The Pennsylvania State University 6OOFV77005
ENVIRONMENTAL ACOUSTICS LABORATORY
110 Moore Building
University Park, Pennsylvania 16802
NOISE TRAINING MANUAL
P.L. Michael
D.M. DeJoy
R.L. Kerlin
A.M. Kohut
J.H. Prout
December 1977
Final Report on Contract No. 68-01-3895
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Noise Abatement and Control
Washington, DC 20460
-------
The Pennsylvania State University
ENVIRONMENTAL ACOUSTICS LABORATORY
110 Moore Building
University Park, Pennsylvania 16802
NOISE TRAINING MANUAL
P.L. Michael
D. M. DeJoy
R.L. Kerlin
A.H. Kohut
J.H. Prout
DECEMBER 1977
Final Report on Contract No. 68-01-3895
U,S, ENVIRONMENTAL PROTECTION AGENCY
Office of Noise Abatement and Control
Washington, DC 20460
-------
FORWORD
Noise is a by-product of our technological society and, until recently,
has been one of the most neglected environmental pollutants. The extent of
the adverse effects of noise on the quality of life and the problems inherent
in noise control are still being realized. Current studies have revealed
that: (1) exposure to noise from common environmental sources may result
in irritability, discomfort, nervous tension, loss of ability to concentrate
effectively, impaired aptitude to perform simple tasks well, loss of sleep,
and stress-related diseases, and (2) most importantly, exposure to high
level noise may cause temporary or permanent hearing loss.
Beginning in the late 1960's, the Federal Government assumed a
leadership role in noise abatement. Initial efforts were directed toward
determining the scope of the national noise pollution problem and in enacting
basic legislation to address this problem. Subsequently, a national noise
control strategy, based on noise abatement at the community level, was
formulated and has recently begun to be implemented.
This manual is a compendium of information considered to be essential
to the development of successful community noise control programs. It
is intended to satisfy the needs of a broad lay audience who will be involved
in the legislative, administrative, and technical aspects of this program.
Because unique problems may be encountered in individual community noise
abatement programs, references have been included at the end of each chapter
to direct the reader to additional resource material. Also, Appendix B to
this manual provides a list of some source reference that are likely to be
useful to persons involved in community noise abatement programs.
The contents of this report were prepared by the authors under contract
with the U.S. Environmental Protection Agency (EPA). The opinions, findings,
and conclusions expressed are not necessairly those of the EPA. Mention of
trade names or commercial manufactures does not constitute an endorsement by
either the EPA or the Pennsylvania State University.
-------
TABLE OF CONTENTS
FORWORD. i i
LIST OF TABLES 1X
LIST OF FIGURES x
1. AUDITION 1-1
1.1 Anatomy of the Ear 1-1
1.1.1 The Outer Ear 1-1
1.1.2 The Middle Ear 1-5
1.1.3 The Inner Ear 1-8
1.2 The Physiology of Hearing 1-8
1.3 Noise-Induced Hearing Loss 1-10
1.3.1 How Noise Damages Hearing 1-11
1.3.2 The Problem at Work 1-11
1.3.3 The Problem Away from Work 1-12
References 1-13
Additional Reading 1-14
2. PHYSICS OF SOUND 2-1
2.1 What Is Sound? 2-1
2.2 How Is Sound Propagated? 2-1
2.3 What Are the Attributes of Sound? 2-3
2.3.1 Amplitude (Loudness) 2-3
2.3.2 Frequency 2-6
2.3.3 Time Distribution 2-9
2.4 What Is Noise? 2-9
Glossary 2-10
Bibliography 2-14
References 2-15
3. COMMUNITY NOISE PROGRAMS 3-1
3.1 Major Elements of a Community Noise
Control Program 3-1
3.1.1 Problem Definition 3-1
3.1.2 Problem Solution 3-1
3.1.3 Guidance System 3-2
3.2 Recommendations for Implementation of an
Effective Community Noise Program 3-2
References 3-6
4. RULES AND REGULATIONS 4-1
4.1 Private and General Nuisance Actions 4-1
4.2 Federal Legislation 4-2
4.2.1 Historical Perspective 4-2
4.2.2 Occupational Noise 4-3
4.2.3 Aircraft/Airport Noise 4-4
4.2.4 Surface Transportation Noise (Highway
and Railroad) 4-5
11.1
-------
4.2.5 Neighborhood Noise 4-7
4.3 State and Local Government 4-7
4.4 Progress Resulting from the Noise Control Act
of 1972 4-9
4.5 Roles and Authority - Toward a National Strategy
for Noi se Control 4-12
References 4-14
5. NOISE ABATEMENT TOOLS 5-1
5.1 General Background Information 5-1
5.1.1 Noise'Control Act of 1972 5-1
5.1.2 Report to the President and Congress
on Noise 5-1
5.1.3 Public Health and Welfare Criteria
for Noise 5-2
5.1.4 Information 'of Levels of Environmental
Noise Requisite to Protect Public Health
and Welfare with an Adequate Margin of
Safety 5-3
5.1.5 EPA Noise Control Program Progress
to Date 5-3
5.1.6 Toward a National Strategy for Noise
Control 5-3
5.2 State and Local Noise Control Legislation 5-4
5.2.1 Model Community Noise Control Ordinance... 5-4
5.2.2 Guidelines for Developing a Training
Program in Noise Survey Techniques 5-5
5.2.3 Chicago Urban Noise Study 5-5
5.2.4 State and Municipal Noise Control
Activities 1973-1974 5-5
5.2.5 Noise Source Regulation in State and Local
Noise Ordinances 5-6
5.3 Community Planning
5.3.1 Handbook for Regional Noise Programs 5-6
5.3.2 FAA Advisory Circular No. 150-5050-4 --
Citizen Participation in Airport Planning. 5-7
5.3.3 DOT Policy and Procedure Memorandum No.
90-2, Noise Standards and Procedures 5-7
5.3.4 Federal Aid Highway Program Manual of
Federal Highway Administration, Volume 7,
Chapter 7, Section 3 -- "Procedures for
Abatement of Highway Traffic Noise and
Construction Noise" 5-7
5.3.5 Department of Housing and Urban Develop-
ment Circular 1390.2, Noise Abatement
and Control 5-8
5.4 Aircraft/Airport and Surface Transportation Noise
Control, Abatement and Enforcement 5-8
5.4.1 Report to Congress on Aircraft/Airport
Noi se '. 5-8
5.4.2 Transportation Noise and Its Control 5-8
5.4.3 Department of Transportation, Bureau of '
Motor Carrier Safety Regulations for
Enforcement of Motor Carrier Noise Emission
Standards 5-9
iv
-------
5.4.4 Department of Transportation, Federal
Railroad Administration Railroad Noise
Emission Compliance Regulations 5-9
5.5 Industrial/Occupational Noise Reduction 5-9
5.5.1 Criteria for a Recommended Standard . .
Occupational Exposure to Noise 5-9
5.5.2 NIOSH Industrial Noise Control Manual 5-10
5.5.3 NIOSH Compendium of Materials for
Noise Control 5-10
5.5.4 Guidelines on Noise 5-10
5.5.5 AIHA Industrial Noise Manual 5-10
5.6 . Miscellaneous Handbooks, Periodicals, and
References 5-11
5.6.1 Quieting: A Practical Guide to Noise
Control 5-11
5.6.2 Commercial Handbooks ." 5-11
5.6.3 Periodicals 5-12
5.7 Standards 5-12
5.8 Environmental Protection Agency Services 5-12
5.8.1 EPA Regional Offices 5-13
5.8.2 Noise Enforcement Division : 5-13
References 5-14
6. HIGH LEVEL NOISE EXPOSURE AND HEARING CONSERVATION. 6-1
6.1 Hazardous Properties of Noi se 6-1
6.1.1 Overall Noise Level 6-1
6.1.2 Frequency Spectrum 6-2
6.1.3 Exposure Duration :-.'..,.. 6-2
6.1.4 Temporal Pattern '. 6-2
6.1.5 Summary 6-2
6.2 How Noi se Damages Heari ng 6-2
6.2.1 Indications of Noise-Induced Hearing Loss. 6-3
6.2.2 Determination of a Hearing Handicap 6-3
6.2.3 Presbycusis and Other Factors Affecting
Hearing 6-4
6.3 Hearing Conservation Programs 6-4
6.3.1 - Assessment of Noise Dose.. .V 6-5
6.3.2 Noise Reduction 6-5
6.3.3 Hearing Assessment 6-6
6.4 Noise Exposure Limits .and OSHA 6-6
6.5 Noise Exposure Limits'and EPA 6-8
References.'.-.:..; ...•'..'.,. .V 6-10
7. . £FFECTS^:-1&:SE;;ON BEHAVIOR AND WELL-BEING 7-1
7;.l Ajft6^a;tfce and Community Response 7-1
• i 7VT.;T Individual Reactions 7-1
, v;7.-l.2 .^Community Reaction 7-1
^J.3^'Complaint Activity 7-2
.;- • 7;vtV4 Noise Ratings ., 7-4
-\7.:-l.i5 Implications of Annoyance and Community
Response 7-4
7.2 Physiological Effects of Noise, Stress and Health 7-4
7.2.1 The N-Response 7-4
-------
Page
7.2.2 Circulatory System Effects 7-5
7.2.3 Pupillary Dilation 7-5
7.2.4 Startle Effects 7-5
7.2.5 Vestibular Effects 7-5
7.2.6 Stress Reactions 7-6
7.3 General and Mental Health 7-6
7.4 Task Performance 7-7
7.4.1 Characteristics of the Nosie, Task, and
Individual 7-8
7.4.2 Cumulative and Post Noise Effects 7-9
7.4.3 Field Studies 7-9
7.4.4 Implications of Task Performance Effects.. 7-10
7.5 Sleep Disturbance 7-10
7.5.1 Stages of Sleep 7-10
7.5.2 Variables Related to Sleep Disturbance 7-10
7.5.3 Implications of the Sleep Disturbance
Effects 7-11
7.6 Speech Interference 7-12
7.6.1 Variables Related to Degree of Speech
Interference. 7-12
7.6.2 Measures of Speech Interference 7-13
7.6.3 Noise Level, Vocal Effort, and Distance... 7-13
7.6.4 Implications of Speech Interference 7-15
References 7-16
8. SOUND PROPAGATION CHARACTERISTICS 8-1
8.1 Spherical and Cylindrical Spreading 8-1
8.2 Absorption Effects from Earth Surfaces and
the Atmosphere 8-2
8.3 Reflection and Transmission Loss from Barriers... 8-6
8.4 Effects of Weather Conditions on Noise
Propagation 8-9
References. 8-10
9. LAND USE PLANNING AND NOISE CONTROL TECHNIQUES 9-1
9.1 Land Use Planning 9-1
9.1.1 Comprehensive Planning 9-1
9.1.2 Zoning .... 9-2
9.1.3 Site Planning 9-3
9.1.4 Building Design ° 9-8
9.1.5 Other Planning Related Techniques 9-9
9.1.6 Summary 9-9
9.2 Physical Noise Control Procedures 9-10
9.2.1 Barriers 9-10
9.2.2 Landscaping 9-12
9.2.3 Combinations of Noise Control Procedures.. 9-15
Appendix A to Chapter 9 9-17
References 9-25
-------
10. SOUND SOURCE CHARACTERISTICS 10-1
10.1 Source Characteristics 10-1
10.1.1 Sound Level ' 10-1
10.1.2 Frequency Distribution 10-2
10.1.3 Temporal Distribution 10-2
10.1.4 Directional Distribution 10-6
10.1.5 Source Operating Conditions 10-9
10.1.6 Description of the Measurement Site 10-9
References 10-10
11. INSTRUMENTATION AND MEASUREMENT METHODOLOGY 11-1
11.1 Sound Level Meters 11-1
11.1.1 Weighting Networks 11-2
11.1.2 Meter Indication and Response 11-2
11.1.3 Microphones 11-4
11.2 Statistical Analysis of SLM Data 11-7
11.2.1 Manual Sampling Procedures 11-8
11.3 Sound Analyzers 11-11
11.3.1 Octave-Band Analyzers 11-12
11.3.2 One-Third Octave-Band Analyzers 11-12
11.3.3 Statistical Analyzers 11-12
11.4 Tape Recorders 11-14
References 11-15
12. COMMUNITY NOISE ATTITUDE SURVEYS 12-1
12.1 Surveys and Survey Instruments (Interviews
and Questionnaires) 12-1
12.2 Sampling 12-2
12.2.1 Simple Random Sample ,. 12-2
12.2.2 Stratified Random Sample 12-3
12.2.3 Cluster Sample 12-3
12.3 Survey Design 12-3
12.3.1 Structured vs Unstructured Interview 12-4
12.3.2 Fixed-Alternative vs Open-Ended
Questions 12-4
12.3.3 Direct vs Indirect Interview 12-4
12.4 Model for the Design of Noise Surveys 12-5
12.5 Survey Content 12-6
12.5.1 Description and Assessment of the
Noise Environment 12-6
12.5.2 Activity Disruption and Interference
from Noise 12-7
12.5.3 Psycho-social and Situational Viriables. 12-7
12.5.4 Personal-demographic Background 12-7
References 12-9
13. SOUND MEASUREMENT LABORATORY AND FIELD EXERCISE... 13-1
13.1 Sound Level Meter 13-1
13.1.1 Instruction Manual 13-1
13.1.2 Operating Controls 13-1
13.1.3 Field Calibration... 13-2
13.2 Analyzers 13-3
vii
-------
Page
13.3 Record Keeping 13-4
13.4 Sound Measurement Laboratory 13-4
13.4.1 Sound Measurement Training Tape 13-4
13.4.2 Use of Recorded Materials 13-9
13.5 Community Sound Measurement 13-10
Appendix A to Chapter 13 13-11
Appendix B to Chapter 13 13-15
Appendix C to Chapter 13 13-17
APPENDIX A: A DISCUSSION OF STRUCTURE-BORNE VIBRATION A-l
APPENDIX B: SOME SOURCE REFERENCES - COMMUNITY NOISE ABATEMENT
PROGRAM : B-l
vn i
-------
LIST OF TABLES
Table Page
7.1 Percentages of Persons Highly Annoyed Who Register
Complaints as a Function of L. . 7-3
8.1 Sound Absorption Coefficients of Material 8-3
9.1 Summary of Noise Levels Identified as Requisite to
Protect Public Health and Welfare with an Adequate
Margin of Safety 9-7
9.2 Barrier Attenuation 9-14
9.3 Effectiveness of Noise Control Procedures 9-16
13.1 Noise Training Tape 13-8
IX
-------
LIST OF FIGURES
Figures Page
1.1 Schematic Drawing of the Human Ear 1-2
1.2 The Exteranl Ear 1-3
1.3 The Middle Ear 1-6
1.4 The Inner Ear 1-9
2.1 Propagation of a Sound Wave 2-2
2.2 Cycle of a Sound Wave and Its Component Parts 2-4
2.3 Sound Waves with the Same Frequency but Different
Amplitudes 2-5
2.4 Relationship Between A-Weighted Sound Pressure ~
Level in Decibels (dB) and Sound Pressure in N/m ... 2-7
7.1 Distance at Which Ordinary Speech Can be Understood
(as a Function of A-weighted Sound Levels of Masking
Noise in the Outdoor Environment) 7-14
8.1 Attenuation for Sound Propagation Through Shrubbery
and Over Thick Grass, Measured Data and Analytical
Approximation. 8-7
8.2 Attenuation for Sound Propagation in Tree Zones,
Measured Data and Analytical Approximation for
Average U.S.A. Forests 8-7
8.3 Distance for 3 dB(A) Deviation Due to Atmospheric
Absorption vs Relative Humidity -- Temperature 68°F
Parameter: Spectral Distribution of Intensity 8-8
9.1 Fixed Source Noise Levels Allowable at Residential
District Boundaries 9-4
9.2 Fixed Source Noise Levels Allowable at Business/
Commerical District Boundaries 9-5
9.3 Fixed Source Noise Levels Allowable at Manufacturing/
Industrial District Boundaries 9-6
9.4 Average Transmission Loss of a Single Barrier as a
Function of Barrier Mass and Percentage of Open
Area 9-11
9.5 Noise Paths From Roadway to Receiver 9-13
9.6 Short-Circuit of Barrier Around Ends 9-13
-------
Figures Page
10.1 Steady-State Continuous Sound 10-4
10.2 Steady-State Intermittent Sound 10-5
10.3 Fluctuating Continuous Sound 10-7
10.4 Fluctuating Intermittent Sound 10-8
11.1 A-, B-, and C-Frequency Weightings as Specified by
ANSI SI.4 -1971 11-3
11.2 Free Field Response of a 1" Pressure Microphone for
Various Angles of Incidence 11-5
11.3 Completed Manual Sampling Data Sheet 11-9
11.4 Noise Survey Data Sheet for Recording Octave-Band
Data 11-13
13.1 Community Noise Survey Data Sheet 13-5
XI
-------
Chapter 1
AUDITION
"It is hearing, with its offspring, speech, that
gives man his superlative capacity to communicate:
to pass along hard-won knowledge, to make use of
that knowledge, and so to rule an entire planet" (1).
Audition is one of man's most complex and intriguing senses. Our
ears have become essential to our survival. They alert us to danger; provide
us the pleasure of music and sound; and, most importantly, allow us to
communicate with each other through speech -- and speech is the basis of
our society. The importance of hearing and speech to man's socialization
is most dramatically seen in those who are hearing impaired. Without
help, these people are often isolated from society, unable to function
in a world that relies on speech, arid incapable of expressing themselves
fully in that world.
The normal healthy human ear is a remarkable and efficient sense
organ. It is sensitive to very low sound pressures that produce a
displacement of the eardrum no greater than the diameter of a hydrogen
molecule, and yet it is capable of transducing sounds more than a million
times louder than this. It also can detect a wide range of frequencies
or pitches from very low to very high. The ear has always intrigued
researchers, and although it has been studied for many years, it still
holds many secrets.
What then is audition? What anatomical structures comprise the ear
and how do they operate? And how can noise damage our hearing? These
questions will be addressed in this chapter.
1.1 Anatomy of the Ear
The ear may be thought of as consisting of three sections: the
outer ear, the middle ear, and the inner ear. These major divisions of
the ear, as well as the various anatomical structures which comprise
them, are shown in Figure 1.1.
1.1.1 The Outer Ear
The outer or external ear has two parts:
1) the pinna or auricle
2) the external auditory meatus or ear canal
These structures are illustrated in Figure 1.2.
-------
AURICLE
ro
INNER EAR
OSSICLES
ACOUSTIC
NERVE
CANAL
EUSTACHIAN
TUBE
FIG, 1,1 SCHEMATIC DRAWING OF THE HUMAN EAR
-------
AURICLE
EAR CANAL
FIG, 1,2 THE EXTERNAL EAR
-------
Pinna or Auricle: The pinna, or auricle, is that structure which
we commonly refer to as our "ear." It is a flap-like appendage fastened
to the side of the head at an angle of 30 degrees (2). In relation to the
contributions of other structures of the ear, the pinna plays only a minor
role in the auditory process. However, it does serve as an aid in sound
localization and also functions to channel'very high frequency sounds into
the ear canal.
The Ear Canal or External Auditory Meatus: The primary function of
the ear canal, or external auditory meatus, is to conduct sound to the
eardrum. The ear canal is a curved, irregularly shaped tube which is
closed at one end by the eardrum. Although the size and shape of the
ear canal differ significantly between individuals and even between
ears of the same individual, the ear canal has certain acoustic properties
which aid the auditory process. The average length of the ear canal is
about 25 to 33 mm (1 to 1 1/3 inch). A tube of this length, when closed
at one end by the eardrum, will produce a resonance at a frequency of
about 3,000 to 4,000 hertz^. This resonance acts to increase the response
of the ear by about a factor of 3 (10 dB). In other words, the ear canal
is structured in such a way that frequencies around 3,000 hertz will be
made to sound around 10 dB louder by the time they have passed through
the canal and have arrived at the eardrum. This acoustic phenomenon
becomes important when one considers that these frequencies fall within
the range of frequencies which comprise human speech.
The ear canal also serves a protective function. It contains both
hairs and wax-secreting glands which prevent the intrusion of foreign
bodies into the canal. Normally, ear wax flows toward the entrance of
the ear canal, carrying with it the dust and dirt that accumulates in
the canal. The normal flow of wax may be interrupted by changes in the
body chemistry that can cause the wax to become hard and to build up
within the ear. Too much cleaning or the prolonged use of ear plugs may
cause increased production of wax, and when the wax builds up to the
point where the canal is occluded, a loss of hearing will result. Any
build-up of wax deep within the ear canal should be removed very carefully
by a well-trained person to prevent damage to the eardrum and middle ear
structures.
The surface of the external ear canal is extremely delicate and easily
irritated. Cleaning or scratching with matchsti.cks, nails, hairpins, etc.,
can break the skin and cause a very painful and persistent infection.
Infections can cause swelling of the canal walls, and occasionally, a loss
of hearing when the canal swells shut. An infected ear should be given
prompt attention by a physician.
Hertz (Hz) is a unit for expressing the frequency of a sound. It is
further defined in Chapter 2.
1-4
-------
1.1.2 The Middle Ear
The middle ear is an air-filled cavity which, as its name so aptly
describes, lies between the outer ear and the inner ear. While the
outer ear functions primarily to direct sound into the canal, the middle
ear acts as a transducer that changes this sound energy, which is in the
form of air pressure variations, into mechanical energy. This transduction
is accomplished through several structures -- the eardrum and three small
bones within the middle ear (2).
The Eardrum or Tympanic Membrane: The eardrum separates the ear canal
from the tympanic or middle ear cavity. The eardrum is a very thin
and delicate membrane that is capable of responding to a wide variation
of sound pressure levels. These changes in sound pressure level actually
displace or move the eardrum very slightly. Although the eardrum is
seldom damaged from displacements caused by common high-level noises, it
may be damaged by a large displacement resulting from the force of an
explosion or rapid change in air pressure. Thus, the often repeated
statement -- "the noise was so loud it almost burst my eardrum" --is
rarely true as a result of exposure to common steady-state noise.
When an eardrum is ruptured, however, the attached middle ear
bones may be dislocated; therefore, the eardrum should be carefully
examined immediately after the injury occurs to determine if it is
necessary to realign the middle ear bones. In a high percentage of
cases, surgical procedures are successful in realigning dislocated ossicles,
so that little or no significant loss in hearing acuity results from this
injury.
The Middle Ear Bones or Ossicles: As shown in Figure 1.3, the middle
ear contains three small bones -- the Malleus (hammer), the Incus (anvil),
and the Stapes (stirrup). These three bones, the smallest in the human
body, serve a dual function:
1) they efficiently deliver sound vibrations to the inner
ear, and
2) they protect the inner ear from receiving vibrations
which could damage it (2).
The ossicles are suspended in the air-filled middle ear cavity
connected to each other and to the walls of the middle ear cavity by
ligaments and muscles. The largest and outermost ossicle , the
malleus, is attached to the eardrum, while part of the stapes (the
innermost ossicle) rests in a small hole in the bone which separates the
air-filled middle ear from the delicate fluid-filled membranes of the
inner ear. This small hole, called the oval window, exposes a portion of
one of the fluid-filled inner ear membranes to the stapes. Thus, the
ossicles form a mechanical link connecting the eardrum to the oval window
of the inner ear. An inward displacement of the eardrum then, will result
in a similar displacement of the ossicles. Therefore, the stapes will
move further into the oval window pushing in on the exposed inner ear
membrane and ultimately displacing the fluid within it.
1-5
-------
I
cr>
MIDDLE EAR
EAR CANAL
FIG, 1,
MIDDLE EAR
-------
The middle ear mechanism (the ossicles and eardrum) therefore is a
mechanical impedance matching device -- that is, it allows pressure
variations in air to be transmitted into pressure variations in fluid with'
very little loss of energy occurring between the two media.
The efficiency of this transmission system is due to the relative
size difference between the eardrum and the oval window (the eardrum has
an area about 20 times that of the oval window), and to the lever action
of the ossicles (the movement of the malleus is greater than that of the
stapes). Because of these conditions, the pressure per unit area becomes
greater at the stapes than at the eardrum. An analagous situation occurs
when hammering a nail into wood. Because the area of the point of the nail
is much smaller than the area of the head of the hammer, the energy
imparted into the nail from the hammer is concentrated into a smaller
area, and thus the energy per unit area is increased, and the nail is
easily driven into the wood.
This complex auditory system also acts in a protective capacity by
mismatching impedances through the involuntary relaxation of coupling
efficiency between the ossicles. In other words, the muscles of the middle
ear can contract and exert tension on the ossicular chain which will
decrease the efficiency of the transmission of energy to the inner ear --
thus protecting it from damage.
The most common problem encountered in the middle ear is infection.
This dark, damp, air-filled space is completely enclosed except for the
small Eustachian tube that connects this space to the back of the throat;
thus, it is very susceptible to infection, particularly in children. If
the Eustachian tube is closed as a result of an infection or an allergy
(see Figure 1.1) there is no way to equalize the pressure inside the
middle ear with that of the surrounding atmosphere. In such an event,
a significant change in atmospheric pressure, such as that encountered in
an airplane or when driving in mountainous territory, may produce a loss
of hearing sensitivity and extreme discomfort as a result of the displace-
ment of the eardrum toward the low-pressure side. Even in a healthy ear
there may be a temporary loss of hearing sensitivity as the result to
the Eustachian tube becoming blocked, but this loss of hearing can be
restored simply by swallowing or chewing gum to momentarily open the
Eustachian tube.
Another middle-ear problem may result from an abnormal bone growth
(otosclerosis) around the middle ear bones, which restricts their normal
movement. The cause of otosclerosis is not totally understood, but
heredity is considered to be an important factor. The type of hearing
loss that results from otosclerosis is generally observed first at low
frequencies. As time passes, it extends to higher frequencies, and
eventually, may result in a severe overall loss in hearing sensitivity.
Hearing aids may often restore hearing sensitivity lost as a result of
otosclerosis, but effective surgical procedures have been refined to such
a point that they are now often recommended.
1-7
-------
1.1.3 The Inner Ear
The inner ear is completely surrounded by bone that protects its
delicate components. As shown in Figure 1.4, it contains both organs for
hearing and for balance. One end of the space inside the bony shell of
the inner ear is shaped like a snail shell and contains the cochlea --
or end organ of hearing. The fluid-filled cochlea, which is only partially
exposed through the oval window, serves to detect and analyze incoming
sound signals and to translate them into nerve impulses that are trans-
mitted to the brain. The other end of the inner ear is shaped like
three semi-circular loops. These bony loops house the membranous semi-
circular canals which contain the sensors for balance and orientation,
In operation, sound energy is transmitted into the inner ear by
the stapes, whose base, you will recall, is coupled to the oval window
of the inner ear. Both the oval window,and the round window located
below it are covered by a thin, elastic membrane which retains the
few drops of fluid within the cochlea. As the stapes forces the oval
window in and out with the dynamic characteristics of the incident sound,
the round window membrane and the fluid of the cochlea are moved with
these same characteristic motions. Thousands of hair cells located along
the two and one-half turns of the cochlea detect and analyze these fluid
motions and translate them into nerve impulses, which are transmitted to
the brain for further analysis and interpretation.
The hair cells w\thin the cochlea may be damaged by old age, disease,
certain types of drugs, and exposure to high levels of noise. Unfortunately,
the characteristics of the hearing losses resulting from these various
causes are often very similar, and it is impossible to determine the
etiology or cause of a particular case.
1.2 The Physiology of Hearing
The preceding section of this chapter discussed the structures and
functions of each of .the three parts of the ear separately. This section
will endeavor to provide an overall view of the functioning of the
auditory system
The function of the auditory system is to change sound pressure
variations in the air into neural impulses which are relayed to the brain
where they are recognized as sound. This process requires a series of
three energy transductions:
1) air pressure vibrations are converted into mechanical
vibrations,
2) mechanical vibrations are converted into pressure
variations in fluid, and
3) pressure variations in fluid are converted into neural
impulses.
1-8
-------
SEMICIRCULAR
CANALS
FIG, 1,4 THE INNER EAR
-------
Each structure of the ear contributes to this transduction process.
Sound incident upon the ear travels through the ear canal to the eardrum.
The combined alternating sound pressures that are incident upon the
eardrum cause the eardrum to vibrate with the same relative characteristics
as the sound source(s). The mechanical vibration of the eardrum is then
coupled through the three bones of the middle ear to the oval window in
the inner ear. The vibration of the stapes in the oval window is trans-
mitted to the fluid contained in the inner ear. (Very high level sounds
may also cause the fluid to be set into motion directly from vibration
of the skull). This fluid movement is detected by thousands of hair cells
which act as transducers, changing physical energy into neural impulses,
which are, in turn, transmitted through the eighth cranial nerve to the
brain for further analysis. It is only when the neural impulses have
reached the brain that we "hear". Thus, audition is an intricate process
requiring many structures -- all necessary contributors to our ability
to hear.
The auditory system is somewhat analagous to a man-made communica-
tions system -- the radio. In much the same way the radio announcer's
voice is transduced several times (from acoustical to electrical to
radio to electrical and back to acoustical energy) before it is finally
received by a listener, sound in the environment must also be transduced
several times in the auditory system before it can be received by the brain.
To continue this analogy, if any part of the radio system is damaged,
such as the microphone or antenna, the message cannot be clearly under-
stood by the receiver, or in some cases, may not be received at all.
The same thing occurs in the auditory system. If damage occurs to any
of the auditory structures they cannot efficiently transduce or transfer
sound energy and a hearing loss will result. The final section of this
chapter will discuss hearing loss caused by noise.
1.3 Noise-Induced Hearing Loss
The number of people who have noise-induced hearing impairment cannot
be accurately assessed because of several factors, three of which are:
1) Hearing test results (the audiogram) are not available
for a significant percentage of our population. Also,
conventional hearing tests are not sensitive to small
changes in hearing.
2) The audiogram can be used to determine total hearing
impairment but it does not provide adequate information
to differentrate between the causes of the hearing loss.
That is, the high frequency loss caused by an over-exposure
to noise is not significantly different from the losses
caused by old age,ototoxic drugs, and childhood diseases.
3) The many different definitions for hearing loss that have
been used by different investigators significantly affect
the estimates proposed for the number of people with losses
or the number of people who are exposed to noise that may
be hazardous.
1-10
-------
One of the most widely accepted estimates of the number of people exposed
to noise that may be hazardous is 40 million, while approximately 80
million persons are in some way affected by noise (3).
1.3.1 How Noise Damages Hearing
Noise-induced hearing loss may be temporary or permanent depending
upon the level and frequency characteristics of the noise, the duration
of exposures, and the susceptibility of the individual.2 Usually tem-
porary losses of hearing sensitivity will diminish so that the original
sensitivities are restored within about sixteen hours (4-6). Permanent
losses are irreversible and cannot be corrected by conventional surgical
or therapeutic procedures.
Noise-induced damage within the inner ear generally occurs in hair
cells located within the cochlea. Hearing acuity is generally first
affected in the frequency range from 2000 to 6000 Hz with most affected
persons showing a loss, or "dip", at 4000 Hz. If high-level exposures
are continued, the loss of hearing will further increase around 4000 Hz
and spread to lower frequencies.
1.3.2 The Problem at Work
Comprehensive data are not available for an accurate determination
of the number of people who have some degree of noise induced-hearing
impairment. However, studies of relatively small groups show that
workers in many industrial areas have sufficient noise exposures to cause
significant hearing impairments (4-6).
The best estimates of the number of persons who have significant
hearing impairment as a result of overexposure to noise are based on a
comparison of the number of those with hearing impairments found in high-
noise work areas and the general population who have relatively low noise
exposures (7). These studies show that significant hearing impairments
for industrial populations are 10% to 30% greater for all ages than for
general populations that have relatively low-level noise exposures. For
example, at age 55, 22% of a group that has had low noise exposures may
show significant hearing impairment while, in an industrial high-noise
exposure group, the percentage is 46%. Significant hearing loss is
defined in many State compensation laws to be greater than 25 dB hearing
level (referenced to the American National Standards Institute, ANSI
S3.6 - 1969 Specifications) averaged at 500 Hz, 1000 Hz and 2000 Hz.
2
The reader is referred to the reference section provided at the end of
this chapter for sources dealing more fully with hearing loss.
1-11
-------
Noise-induced hearing loss is a particularly difficult and insidious
problem because a person does not usually know that his hearing is being
affected, and the damage usually develops over a long period of time so
that the loss of hearing may not be apparent until a considerable amount
of damage has been accrued. Even after incurring a significant amount of
damage, a person with noise induced hearing loss will be able to hear
common, low frequency (vowel) sounds very well, but he will miss the
high frequencies (consonants) so important in speech. He will hear people
talking at loudness levels that are nearly normal, but he may not be able
to understand what they are saying. A noise-induced hearing loss becomes
particularly noticeable when speech communication is attempted in noisy
places, such as in a room where many people are talking, or where a radio
is playing loudly, or in a car moving a high speed with the windows open.
1.3.3 The Problem Away from Hork
An additional concern is that many individuals may be exposed to
harmful noises while away from work. Many people are often exposed to
potentially hazardous noises that might come from guns, power tools,
lawnmowers, airplanes, subways, race cars, loud music, or even from
riding at high speed in a car with windows open.
1-12
-------
REFERENCES
1. Stevens, S. S. and Warshofsky, F., Sound and Hearing, Time-Life
Books, Time Inc., N.Y., 1970.
2. Zemlin, Willard A., Speech and Hearing Science, Prentice-Hall Inc.,
Englewood Cliffs, N.J., 1968.
3. "Report to the President and Congress on Noise" U.S. Environmental
Protection Agency, Office of Noise Abatement and Control, Washington,
D.C. 20460. EPA Document No. NRC 500.1 December 31, 1971 (GPO Stock
No. 5500-0040) (NTIS No. PB-206-716).
4. Occupational Safety and Health Standards (Williams-Steiger Occupational
Safety and Health Act of 1970), U.S. Department of Labor, Federal
Register, May 29, 1971.
5. "Occupational Exposure to Noise," U.S. Department of Health, Education
and Welfare, National Institute for Occupational Safety and Health,
1972.
6. "Information on Levels of Environmental Noise Requisite to Protect
Public Health and Welfare with an Adequate Margin of Safety," U.S.
Environmental Protection Agency, March, 1974.
7. "Noise as a Public Health Hazard," American Speech and Hearing
Association, Report No. 4, pp. 105-109* Feb. 1969.
1-13
-------
ADDITIONAL READING
Newby, Hayes A., Audiology, Appleton-Century-Crofts Educational
Division, Meredith Corp., N.Y. 10016, 1964.
Sataloff, J. and Michael, P.L., Hearing Conservation, Charles C. .
Thomas, Publisher, Bannerstone House, 301-327 East Lawrence Ave.,
Springfield, Illinois, 1973.
1-14
-------
Chapter 2
PHYSICS OF SOUND
This chapter was written for those readers who are unfamiliar with
the characteristics of sound and its propogation, and therefore presents
this information at a rather elementary level. For those readers who
require a more comprehensive treatment of this subject, a list of references
has been compiled and is presented at the end of the chapter. A glossary,
defining most of the terms that may be encountered in readings in this
area, has also been included.
2.1 what Is Sound?
The nature of sound is often debated with the following question:
if a tree falls in the forest, and no one is near to hear it fall, is
there a sound? In other words, does sound deal with a cause (a vibrating
object such as the falling tree) or with an effect (the sensory experience
of hearing)? The answer is that sound is both these things. It is both
a physical event and a physiological sensation (l).
The sensation of sound is a result of oscillations in pressure,
particle displacement, and particle velocity, in an elastic medium
between the sound source and the ear. Sound is caused when an object is
set into vibration by some force. This vibration causes molecular move-
ment of the medium in which the object is situated, thereby propagating
a sound wave. Sound is "heard" when a sound wave impinges on the human
ear and is recognized by the brain. Further, the characteristics of
the sound wave must fall within the limitations of the human ear for the
sound to be heard because the human ear cannot hear all sounds. Sound
frequencies (pressure variation rates) can be too high (ultrasonic) or
too low (infrasonic), or the sound amplitudes may be too soft to be heard
by man.
2.2 How Is Sound Propagated?
Sound in transmitted from the sound source to the ear by the movement
of molecules in the medium. This molecular movement is called a sound
wave.
In air, sound waves are described in terms of propagated changes in
pressure that alternate above and below atmospheric pressure. These
pressure changes are produced when vibrating objects (sound sources)
cause alternate regions of high and low pressure that propagate from the
source. In the production of airborne sound waves, the vibrating sound
source actually "bumps" into the adjacent air molecules forcing them to
move (see Figure 2.1). These molecules, in turn, bump into others
-------
ro
FIG. 2.1 PROPAGATION OF A SOUND WAVE
-------
further away from the source, and so on. Thus, the energy from the sound
source is imparted to the air molecules and thereby is transmitted through
the medium. Note that sound energy and not air particles travel from the
source through the medium. An analagous situation occurs when dropping
a pebble into a still pond. When the pebble hits the water, it causes a
wave motion to emanate from it in all directions, moving outward in
concentric spheres.
There are two phases to a sound wave: compression and rarefaction.
The compression phase occurs when the air molecules are forced closely
together (causing an instantaneous increase in air pressure) and the
rarefaction phase occurs when the air molecules are pulled apart from each
other (causing an instantaneous decrease in atmospheric pressure). This
complete sequence of one compression and one rarefaction is called a
cycle. The cycle of a sound wave and its component parts are illustrated
in Figure 2.2.
2.3 What are the Attributes of Sound?
Sound has several attributes by which it may be characterized. We
have all learned to describe these attributes subjectively. That is, we
refer to sounds as varying in pitch, in loudness, and in quality. However,
these same attributes of sound may be measured objectively and, as such,
are termed frequency, amplitude and time distribution.
2.3.1 Amplitude (Loudness)
The preceding section has shown that the frequency of a sound wave
is dependent on the rate at which the sound source vibrates. The faster
its rate of vibration, the higher the frequency of the sound generated.
The amplitude of sound, however, depends on the amount of displacement of
the vibrating source.
The subjective correlate of amplitude is loudness. Thus, the higher
the amplitude or level of sound, the louder we perceive it, although there
is not a one to one relationship between the physical amplitude of sound
and the sensation of loudness. Figure 2.3 illustrates sounds which have
the same frequency but vary in level.
The ear is sensitive to a wide range of sound levels and this creates
many difficulties in working with absolute sound pressure units. For
instance, the human ear is sensitive to a pressure range greater than
0.00002 to 20,000 newtons per square meter. Because of the awkwardness
and difficulty of working with such a broad range of absolute units, the
decibel has been adopted to compress this large range and more closely
follow the response of the human ear.
2-3
-------
ro
ATMOSPHERIC
PRESSURE
COMPRESSION
(INCREASE IN PRESSURE)
RAREFACTION
(DECREASE IN PRESSURE)
ONE CYCLE
FIG, 2,2 CYCLE OF A SOUND WAVE AND ITS COMPONENT PARTS,
-------
A
B
f
/
FIG, 2,3 SOUND WAVES WITH THE SAME FREQUENCY BUT
DIFFERENT AMPLITUDES,
2-5
-------
The decibel : The decibel (abbreviated dB) is a convenient means for
describing sound pressure level: the logarithmic level of sound pressure
above an arbitrarily chosen reference, 0.00002 newtons per square meter
(N/m2). This reference pressure can also be expressed as 20 micropascals
(yPa). In other words the decibel is based on a ratio comparing two sound
pressures. One sound pressure is that which we wish to quantify and the
Other sound pressure is termed a reference. The reference represents
approximately the minimum audible threshold of the normal ear. The
decibel, then is based on a ratio expressing how much greater a sound
pressure is than the least. sound pressure we can hear, and it is expressed
as a level above the specified reference pressure.
L = 20
The formula for determining the sound pressure level is:
P
where p-j is the sound pressure at the measurement location and p0 is the
reference pressure of 20 MPa. Figure 2.4 relates decibel values to sounds
commonly heard in our environment.
As sound increases beyond normal exposure levels, it will first cause
discomfort, then tickle, and finally, pain (in the region from 110 through
130 dB sound pressure level). Permanent and irreversible damage to hearing
may result from extended exposures to sound levels well below those that
cause tickle and pain sensations.
2.3.2 Frequency
Frequency is defined as the number of complete pressure variations,
or cycles, per second of a sound wave. As discussed earlier, one cycle
is equal to one complete compression and rarefaction variation of a
sound wave.
The unit for expressing frequency is cycles per second, abbreviated
c.p.s., c/s, cps, or hertz, abbreviated Hz. The latter term is now in
more general use. Thus, if a sound source vibrates 500 times per second,
it produces a sound with a frequency of 500 cps or 500 Hz. The terms
kilohertz (kHz) is also frequently used and means 1000 cycles per second
or 1000 Hz. Thus, a 4000 Hz tone may be expressed as 4kHz.
Frequency is directly related to the subjective sensation of pitch.
The term pitch indicates that the human ear is involved in the evaluation
of the sound. The lower the frequency of a sound, the lower we perceive
its pitch. Therefore, a sound with a frequency of 250 Hz will sound much
lower in pitch than a sound with a frequency of 2000 Hz.
2-6
-------
SOUND PRESSURE LEVEL
(dB re 20/i Pa)
120
SOUND PRESSURE
(Pa)
PNEUMATIC CHIPPER (at5ft)
TEXTILE LOOM
NEWSPAPER PRESS
DIESEL TRUCK40mph (at50ft)
110-
100 - - 2
90-
80
70-
ro
i
PASSENGER CAR 50mph (at50ft)
CONVERSATION (at 3 ft) 60
^0.5
+ 0.2
5-0.1
-0.05
5O-
QUIETROOM 4O--0.002
r 0.001
•
-O.OOO5
30H
20 —
O-1-
20
10
5
- - 0.02
=-0.0
=• 0.005
TEENAGE ROCK-N-ROLL BAND
POWER LAWN MOWER (at operator's ear)
MILLING MACHINE (at 4ft)
GARBAGE DISPOSAL (at 3ft)
VACUUM CLEANER
AIR CONDITIONING WINDOW UNIT (at 25ft)
O.OOO2
rO.OOOl
-OOOOO5
OOOOO2
FiGURE2.il RELATIONSHIP BETWEEN
A-WEIGHTED SOUND PRESSURE LEVEL
IN DECIBELS (dB) AND SOUND PRESSURE
IN PA, -
, /
-------
Sound can consist of a single frequency (called a pure tone) or a
combination of many frequencies (called a complex tone). Very few sound
sources produce pure Atones, although a flute almost produces one. Most
sounds in our environment are complex sounds -- that is, they are actually
a combination of many separate pure tones which exist simultaneously and
vary in level. The manner in which these separate tones are combined is
the spectrum of a sound.
Because the frequency range is so broad, it is frequently divided
into numerous bands. Division into octave bands, for example, is con-
venient when measuring sound and will be discussed in Chapter 11. An
octave band is a frequency bandwidth that has an upper band-edge
frequency equal to twice its lower band-edge frequency. The most frequently
used octave bands in sound measurement are geometrically centered at 31.5,
63, 125, 250, 500, 1000, 2000, 4000, and 8000 Hz. For example, all
frequencies between 707 and 1414 Hz comprise one octave band centered at
1000 Hz (see Chapter 11'). The next octave band includes all frequencies
from 1414 Hz through 2828 Hz and is centered at 2000 Hz. It should be
noted that as the octave band increases in center frequency, the width of
the band increases also. For example, the 1000 Hz octave band has a width
of 707 Hz, while the 2000 Hz octave band has a width of 1414 Hz.
The human ear operates within certain frequency limitations. A
healthy young person can hear normal sound levels over a range of
frequencies from about 20 to 20,000 Hz. However, sounds with different
frequencies are not all perceived with equal loudness. The ear is most
sensitive to sounds between 1000 and 4000 Hz. Generally, the ear's sensi-
tivity falls off as frequencies increase above 4000 Hz and as they decrease
below 1000 Hz.
Sounds outside the audible frequency range are sometimes termed
ultrasonic or infrasonic. Ultrasonic sounds have frequencies above the
normal upper limits of the audible frequency range -- they are too high
to be heard by most human ears. Examples of ultrasonic sounds are those
which are produced by a dog whistle, ultrasonic cleaners, or welding
devices. Infrasonic sounds, on the other hand, are those whose frequencies
are below the normal lower limits of the audible frequency range -- they
are too low to be heard by most human ears. Infrasonic sounds are normally
created by very large sound sources such as ventilating systems or wind
tunnels.
Although ultrasonic and infrasonic sounds are not audible to many
people, they can be heard or "felt" by a significant number of sensitive
persons, and the stress of these exposures may be harmful to some (2).
Maximum exposure limits have been proposed by an ANSI Mriting Group (2).
2-8
-------
2.3.3 Time Distribution
The time distribution of sound may be classified broadly under three
noise temporal patterns:
1) Steady-state
2) Time-varying / Fluctuating
3) Impulsive
Both the steady-state and time-varying categories can be divided into
continuous or intermittent patterns. That is, there can be continuous
or intermittent steady-state noises as well as continuous or intermittent
fluctuating noises. Details on the classification of these temporal
patterns and measurement methodologies to be used for each of the patterns
are provided in Section 10.1.3
2.4 What Is Noise?
Most of this chapter was devoted to defining sound and its
attributes. But what about noise? What is it, and what are its
attributes?
Actually, noise has no specific attributes. It can simple be defined
as unwanted sound. Our perception of sound as noise is very individual
and depends, to a large extent on our emotional state and our activities
during exposure to the sound. For example, music may be appreciated during
moments of relaxation; however for certain individuals it may be very
distractig or annoying if they are concentrating on a particular task,
listening carefully to a faint communication, or trying to sleep. Further
details on human response to sound exposures may be found in Chapter 7.
2-9
-------
GLOSSARY
Acoustic Intensity - (see Sound Intensity).
Acoustic Power - (see Sound Power).
Acoustic Pressure - (see Sound Pressure).
Ambient Noise - Ambient noise may be defined as the overall composite
of sound in a given environment.
Amplitude - The amplitude is the amount of sound at a given location
away from the source, or the overall ability of the source to
emit sound. The amount of sound at a location away from the
source is generally described by the sound pressure or sound
intensity, while the ability of the source to produce sound is
described by the sound power of the source.
Anechoic Room - An anechoic room has essentially no boundaries to
reflect sound energy generated therein. Thus, any sound field
generated within an anechoic room is referred to as free-field.
Audiogram - An audiogram is a record of hearing threshold levels as a
function of frequency, The threshold levels are referenced to
statistically normal hearing threshold levels.
Audiometer - An audiometer is an instrument for measuring hearing
sensitivity.
Critical Band - A critical band is a bandwidth within a continuous-
spectrum noise that has a sound power equal to that of a single-
frequency tone centered in the critical band and just audible in
the presence of the critical bandwidth of noise.
Cycle - A cycle of a periodic function is the complete sequence of
values that occur in a oeriod.
Cycle per second - (see Frequency).
Decibel - The decibel is a convenient means for describing the
logarithmic level of sound intensity, sound power, or sound
pressure above arbitrarily chosen reference values (see text).
Diffuse Sound Field - A diffuse sound field has sound pressure levels
that are essentially the same throughout, and the directions of
propagation are wholly random in distribution.
Effective Sound Pressure - The effective sound pressure at a given
location is found by calculating the root-mean-square value of
the instantaneous sound pressures measured over a period of time
at that location.
MO
-------
Free field - A free field exists in a homogeneous isotropic medium
free from boundaries. In other words, the reflections from
boundaries are negligible in a free field. In a free field,
sound radiated from a source can be measured accurately without
influence from the test space. True free-field conditions are
rarely found, except in expensive anechoic (echo-free) test
chambers; however, approximate free-field conditions exist in
any homogeneous space where the distance from reflecting surfaces
to the measuring location is much greater than the wavelengths
of the sound being measured.
Frequency - The frequency of sound describes the rate at which complete
cycles of pressure are produced by the sound source. The unit
of frequency is the cycle per second (cps) or preferably, the
hertz (Hz). The frequency range of the human ear is highly depen-
dent upon the individual and the sound level, but a person with
normal hearing will have a frequency range of approximately 20
to 20,000 Hz at moderate sound levels. The frequency of a
propagated sound wave heard by a listener will be the same as
the frequency of the vibrating source if the distance between
the source and the listener remains constant; however, the
frequency detected by a listener will increase or decrease as
the distance from the source is decreasing or increasing
(Doppler effect).
Hertz - (see Frequency).
Infrasonic Frequency - Sounds of an infrasonic frequency are below
the audible frequency range.
Intensity - (see Sound Intensity).
Level - The level of any quantity, when described in decibels, is the
logarithm of the ratio of that quantity to a reference value in
the same units as the specified quantity.
Loudness - The loudness of sound is an observer's impression of its
amplitude, which includes the response characteristics of the ear.
Noise - The terms "noise" and "sound" are often used interchangeably
but, generally, sound is descriptive of useful communication or
pleasant sounds, such as music; whereas, noise is used to describe
dissonance or unwanted sound.
Noise Reduction Coefficient - The noise reduction coefficient (NRC) is
the arithmetical average of the sound absorption coefficients of
a material at 250, 500, 1000, and 2000 Hz.
2-11
-------
Octave Band - An octave band is a frequency bandwidth that has an upper
band-edge frequency equal to twice its lower band-edge frequency.
One-Third .Octave Band - A frequency band whose cut-off frequencies
have a ratio of 2 V3, which is approximately 1.26. The cut-off
frequencies of 891 Hz and 1123 Hz define a third-octave band in
common use.
Peak Level - The peak sound pressure level is the maximum instantaneous
level that occurs over any specified time period.
Period - The period (T) is the time (in seconds) required for one
cycle of pressure change to take place; hence, it is the reciprocal
of the frequency.
Pitch - Pitch is a subjective measure of auditory sensation that relates
primarily to the frequency of a sound.
Power - (see Sound Power).
Pure Tone - A pure tone is a sound wave whose instantaneous sound
pressure is a simple sinusoidal function of time.
Random-Incidence Sound Field - (see Diffuse Sound Field).
Random Noise - Random noise is made up of many frequency components
whose instantaneous amplitudes occur randomly as a function
of time.
Reverberation - Reverberation occurs when sound persists after direct
reception of the sound has stopped. The reverberation of a space
is specified by the "reverberation time", which is the time required,
after the source has stopped radiating sound, for the rms sound
pressure to decrease 60 dB from its steady-state level.
Root-Mean Square Sound Pressure - The root-mean-square (rms) value
of a changing quantity, such as sound pressure, is the square
root of the mean of the squares of the instantaneous values of
the quantity.
Sound - (see Noise).
Sound Intensity - The sound intensity (I) at a specific location is
the average rate at which sound energy is transmitted through
a unit area normal to the direction of sound propagation. The
units used for sound intensity are joules per square meter per
second. Sound intensity is also expressed in terms of a level
(sound intensity level, LT) in decibels referenced to -IQ-^ watts
per square meter.
Sound Power - The sound power (P) of a source is the total sound energy
radiated by the source per unit time. Sound power is normally
expressed in terms of a level (sound power level, Lp) in decibels
referenced to 10-12 watts.
2-12
-------
Sound Pressure - Sound pressure (p) normally refers to the rms value
of the pressure changes above and below atmospheric pressure when
used to measure steady-state noise. Short-term or impulse-type
noises are described by peak pressure values. The unit used to
describe sound pressures is the pascal (Pa) where one pascal
equals one newton per square meter (N/m2). Sound pressure is also
described in terms of a level (sound pressure level, Lp) in decibels
reference to 1/X/1Q-5 Pa.
Standing Haves - Standing waves are periodic waves that have a fixed
distribution in the propagation medium.
Transmission Loss - Transmission loss (TL) of a sound barrier may be
defined as ten times the logarithm (to the base 10) of the ratio
of the incident acoustic energy to the acoustic energy transmitted
through the barrier.
Ultrasonic - The frequency of ultrasonic sound is higher than that of
audible sound.
Volume Unit - The volume unit (VU) is used for expressing the magnitude
of a complex waveform such as that of speech or music.
Velocity - The speed at which the regions of sound-producing pressure
changes move away from the sound source is called the velocity of
propagation. Sound velocity (c) varies directly with the square
root of the density and inversely with the compressibility of
the transmitting medium as well as with other factors; however,
in a given medium, the velocity of sound is usually considered
constant under normal conditions. For example, the velocity of
sound is approximately 344 M/sec (1,130 ft/sec) in air, 1432
M/sec (4,700 ft/sec) in water, 3962 M/sec (13,000 ft/sec) in wood
and 5029 M/sec (16,500 ft/sec) in steel.
Havelength - The distance required to complete one pressure cycle is
called one wavelength. The wavelength, a very useful tool in
noise control, may be calculated from known values of frequency
(f) and velocity (c): A = c/f.
White Noise - Hhite noise has an essentially random specturm with
equal energy per unit frequency bandwidth over a specified
frequency band.
2-13
-------
BIBLIOGRAPHY
As an aid to the reader, the following list of source books is
provided with a brief comment on the specific application of each book:
Acoustic Noise Measurements, J. T. Broch, Bruel & Kjaer, Denmark
(1971).Intended as a guide for the application of B and K
equipment in sound measurement, this text provides reliable
technical background in physics of sound.
Fundamentals of Acoustics, L. E. Kinsler and A. R. F. Frey, Wiley
& Sons, Ind., New York (1962). Detailed text for the advanced
acoustics student: requires knowledge of physics and calculus.
Handbook of Noise Measurement, A. P. G. Peterson and E. E. Gross, Jr.,
General Radio Co., Concord, Mass. (1972). Basic overview of
physics of sound and sound measurement techniques for the reader
with limited physical science background.
Hearing Conservation, J. Sataloff and P. L. Michael, C. C. Thomas,
Springfield, Illinois, (1973). Basic text on the physics of
sound and the effects of sound on people that is well suited
to a beginning learner in science of sound.
Sound and Hearing, S. S. Stevens and F. Warshofsky, Time-Life Books,
New York, (1970). Very basic and simplified overview of the
physics of sound and the phenomenon of hearing; this book is
especially useful because of the'exceptional photographs and
drawings used to illustrate various acoustic phenomena.
2-14
-------
REFERENCES
1. Stevens, S.S. and Warshofsky, F., Sound and Hearing, Time-Life Books,
Time Inc., N.Y.., 1970.
2. Michael, P., Kerlin, R., Bienvenue, G. and Prout, J., "An Evaluation
of Industrial Acoustic Radiation Above 10 kHz," Final Report on
Contract No., HSM-99-72-125, U.S. Department of Health, Education,
and Welfare, Public Health Service Center for Disease Control,
National Institute for Occupational Safety and Health, Feb. 1974.
2-15
-------
Chapter 3
COMMUNITY NOISE PROGRAMS
Noise has become a major detractor from the quality of life in
both large and small communities, and it has become apparent that
without some form of community intervention, noise pollution levels will
only increase. Fortunately, communities are becoming aware of the need
to develop and implement effective noise control programs. This chapter
outlines the major elements that should be considered in developing
a comprehensive community noise program. Recommendations for implementa-
tion of an effective community noise control program are also presented.
3.1 Major Elements of a Community Noise Control Program
The major elements of a comprehensive noise program are:
1) problem definition
2) problem solution
3) a guidance system (1)
Each of these elements will be discussed below.
3.1.1 Problem Definition
Before a community can take positive steps to reduce noise, an
analysis of the noise environment of the community must be carried out.
Information concerning the sound levels and sound sources present in the
area must be obtained, and this information should be supplemented by
an assessment of the residents' reactions to these sounds. Problem
definition usually involves the use of sound measurement and social
surveys. Sound measurements in an area are used to identify major sound
sources. Social surveys provide information concerning the subjective
reactions of the citizenry to these sounds and their attitudes toward
the sources. Complaint activity is also a useful index of human reactions
to noise but it is almost always an underestimation of annoyance. (A
more comprehensive discussion of survey instruments, design, and techniques
is presented in Chapter 12.)
3.1.2 Problem Solution
This program element involves the determination of what constitutes
a desirable noise environment and how such an environment can be achieved.
Therefore, program goals must be formulated and alternative means of
achieving these goals must be carefully considered. It is usually best
to state the program goals in quantitative terms; that is, specific
noise level, standards should be specified. The federal EPA Levels and
Criteria documents (2,3) provide information concerning those levels of
noise that are safe. Each community faces unique noise pollution problems,
-------
however, and should carefully consider the costs and benefits to .the
community before adopting noise level standards. The community must .
determine those aspects of the noise problem that are the most serious,
and these should receive priority consideration. It must be determined
in each instance if control measures should be directed at the noise
source, path, or receptor. Generally, it is most effective to control
the source of the noise, but this is not always possible. Consideration
must also be given to the control technology available and its attendent
costs and personnel requirements. At this point, the community needs
to develop an action plan.
3.1.3 Guidance System
This program element refers to the steps that are necessary in
order to insure that the goals specified in the problem solution phase
of the program are achieved. The guidance system must be legal, cost
effective, and enforceable. In order for a program to be effective, it
must be enforceable, otherwise, it is only a "paper program". The
guidance system should also include provisions for program evaluation.
3.2 Recommendations for Implementation of an Effective Community
Noise Program
The preceding sections have outlined the major elements of a community
noise program. At this point, it is appropriate to offer some specific
recommendations concerning the means by which such a program might be
implemented.
1) A community should adopt a comprehensive noise ordinance with
realistic yet beneficial quantitative noise criteria.
As of 1977 more than 900 municipalities in the U.S. had some form
of noise ordinance. This represents a 300% increase since 1970. (4)
Unfortunately, not all of these ordinances employ quantitative or per-
formance type standards, but the trend is clearly toward this type of
ordinance, primarily because they are more enforceable. Quantitative
or performance type ordinances are based upon sound level criteria,
hence, they are more objective in nature. These ordinances usually
specify maximum allowable noise lev.els using the A-frequency weighting,
dB(A). Nonquantitative or nuisance type regulations define unlawful
noise in subjective terms. These laws, which prohibit noises that are
deemed unnecessary and excessive, have proven difficult to enforce.
The Federal EPA in conjunction with the National Institute of
Muncipal Law Officers have developed a model community noise ordinance
(5). This ordinance contains provisions for quantitative regulations
for land use and zoning, motor vehicles and other sources of community
noise. In addition, a nuisance type provision for noise disturbances
is also included. The ordinanace is flexible enough to be modified to
the needs of both large and small communities. An ordinance of this
type should constitute an integral part of a community noise program.
3-2
-------
2) An efficient enforcement program should be established
Once realistic quantitative standards have been specified, the
community must develop practical and workable enforcement procedures.
Reliable noise monitoring equipment and trained personnel must be
available. Staffing and equipment requirements must be fulfilled before
enforcement can take place. The major roadblock is inadequate funding.
Without fiscal support for enforcement, the community is left with only
a "paper regulation." As might be expected, it is the smaller communities
that experience the greatest difficulty in funding their noise control
efforts. Larger cities are usually able to hire environmental protection
or noise control officers, while smaller cities are often forced to
rely on already overburdened police officers. Some additional aspects
of the funding and manpower problem will be discussed later.
Florida has initiated'a program in which it utilizes its State
University System to aid local noise control programs. Five universities,
located in different regions of the state, are under contract to the
state for the purposes of providing technical and training services to
the local programs (6). This includes services ranging from providing
basic noise information to city officials and conducting preliminary
noise surveys, to the training fo enforcement personnel.
3) A good community noise program should include a public awareness
campaign.
The citizens of the community should be educated as to the need
for noise abatement and each citizen's role in reducing community
noise pollution. Much of the success of the Memphis, Tennessee
noise control program has been attributed to their large scale education
campaign (7). The cooperation of civic groups, newspapers, advertising
media, youth groups, and schools should be sought in reaching the public.
4) A preventative noise control program should be established
to identify and prevent future noise problems before they occur.
It is almost always easier to design a quiet product than to reduce
the noise coming from a noisy product. The community should establish
some form of formal review process in which careful attention is given
to the noise impact of proposed buildings, subdivisions, transportation
facilities, etc. The developer should be required to prepare an analysis
of noise impact for the proposed sites. Noise should be an element in
the community's comprehensive planning activities and in its land use
and zoning regulations (see Ch. 9). The community should also consider
the noise emission characteristics of the equipment and machinery it
purchases. This is especially so for objects such as air compressors,
trucks and tractors, and power tools.
3-3
-------
5) The community should establish a continuing evaluation and
monitoring program to determine the effectiveness of its effort to control
noise.
An attempt should be made to determine if the noise program is
achieving its stated goals. It is almost inevitable that experience will
dictate that changes should be made in certain aspects of the program.
A specific mechanism for evaluation should be built into the program
prior to program implementation. The impact of noise sources that are
beyond the jurisdiction of the locality such as aircraft noise should
be continually monitored so that this data can be used as evidence to
support requests for regulations by the Federal Government.
6) The successful community noise program requires adequate
funding and management.
A noise control program without an adequate budget is virtually
useless. As mentioned earlier, a large proportion of the program's
funds must be committed to staff training and equipment purchase. As
of 1973, a full 90% of community noise ordinances of all types had no
fiscal support (8). Attempts must be made to obtain local support and
to seek sources of state and federal funding.
The level of staffing that a program can maintain is directly propor-
tional to its budget. Large cities such as New York and Chicago have
large full-time professional staffs. New York has a staff of over 40,
while Chicago has more than 20 full-time professionals. Smaller cities
such as Ingelwood, California and Boulder, Colorado also have at least
one full-time trained professional. Where possible, enforcement respon-
sibilities should not be given to police personnel if active enforcement
is expected. In most communities police are already overworked, and
under such circumstances noise ordinance enforcement becomes just
another low priority activity.
Communities of the same approximate population often differ greatly
in the extent and severity of their noise problems. It is thus very
difficult to specify staff requirements by population. It is possible
that in somecities with populations of about 50,000 one full-time
professional could do an adequate job of program management and enforce-
ment provided he/she had some form of part-time assistance. However,
in other cities of similar size this would be totally inadequate. But,
in communities of any size, the success of the program depends on good
management. The noise control activities of the community should be
centralized in a single office, preferably with noise control as its sole
responsibility. When control is fragmented "few, if any, of the responsible
agencies view noise control as principal-- or even an important mission
(9 p 210)". The noise control office should be able to deal effectively
with other municipal agencies, and serve as the focal point of community
noise activity. It is this need for management and coordination as much
as the need for enforcement that necessitates that any program regardless
of size should have at least one full-time staff member.
3-4
-------
In establishing the community noise program, consideration should
also be given to the formation of a Noise Control Advisory Council. Such
a body could provide recommendations for the development of the program,
stimulate public interest in noise abatement, and participate in program
evaluation. In some communities Hearing Boards have been utilized to
hear cases regarding ordinance violations or requests for variances.
This approach avoids overburdening existing courts.
3-5
-------
REFERENCES
1. "Promoting Environmental Quality Through Urban Planning and Control",
Environmental Protection Agency, Environmental Studies Division, 1973.
2. "Information on Levels of Noise Requisite to Protect Public Health
and Welfare with an Adequate Margin of Safety," U.S. Environmental
Protection Agency, March, 1974. 'EPA Document Number EPA-550/9-74-004.
3. "Public Health and Welfare Criteria for Noise," U.S. Environmental
Protection Agency, July, 1973. EPA Document Number EPA-550/9-73-002.
4. Bragdon, C.R., "Environmental Noise Control Programs in the United
States." Sound and Vibration December 1977 pp 12-16.
5. "Model Community Noise Control Ordinance," U.S. Environmental Protec-
tion Agency, Sept., 1975. EPA Document Number EPA-550/9-76-003.
6. "Local Noise Programs in Florida," State of Florida Department of
Pollution Control, 1975.
/
7. "Chicago Urban Noise Study," Chicago Department of Environmental
Control, 1970.
8. Bragdon, C.R., "Municipal Noise Ordinances," Sound and Vibration.
December, 1973.
9. Council on Environmental Quality, "Environmental Quality Third
Annual Report," Washington, D.C.: U.S. "Government Printing Office,
1972.
3-6
-------
Chapter 4
RULES AND REGULATIONS
"The essential problem in a legislative approach
to the control of noise is that of weighing the
rights of the individual versus the needs of the
community. Each individual in a society is expected
to suffer a certain amount of annoyance or inter-
ference. The amount to be borne depends on the
society's weighting of the harm to the individual
against the utility to other segments of society
-- in this case, the producers of noise. The type
of legislation of a particular political jurisdic-
tion determines the balance between these two
considerations" (1).
This statement provides a perspective from which to view the
complexities inherent in the formulation of rules and regulations for
the control of noise. Further, an additional factor that complicates
the problem of noise legislation a'nd enforcement is the problem of
conflicts between government units arising from disputes over jurisdic-
tional boundaries. For instance, a particularly noisy area, such as a
major airport facility, may fall under the jurisdiction of several agencies.
Also, certain aspects of legislative control can be pre-empted by a superior
authority, as in the case of some major sources of transportation noise.
For example, the Federal Government pre-empts jurisdiction for noise
control of jet aircraft and interstate tractor-trailer vehicles.
Consequently, there is a continuing need for clarification and delegation
of authority and responsibilities between Federal, State, and local units
of government.
4.1 Private and General Nuisance Actions
There is a clear need for control of noise through appropriate
and effective legislation and enforcement. Civil actions, under the
common law guarantee of protection from a nuisance, are neither effective
nor, in many cases, warranted. Remedies must be decided on the merits of
each case and by appropriate judicial action. Thus, the time and costs
involoved can be prohibitive. This is especially true in light of the
fact that a favorable noise abatement solution may be doubtful if the
noise creating activity is justifiable because of its' service or benefits
to a certain section of society. In addition, enforcement of general
nuisance statutes regarding noise are not generally effective. Those
officials assigned to administer and enforce a nuisance ordinance may
be neither inclined nor encouraged to do so. For example, local police
often must give a lower priority to such tasks than to ones more clearly
related to their duties for crime protection.
-------
4.2 Federal Legislation
The most promising means for the abatement and prevention of
environmental noise pollution is through the enactment of effective
legislation. Thus, suitable ordinances may be enacted to deal with the
major sources of noise found in the areas of industrial, aircraft, surface
transportation, and neighborhood noise. However, in order for legislation
to be effective, it must include rules, regulations, and/or standards that
are based on quantitative measures of noise. The use of quantitative
measures allows for easy determination and enforcement of noise abatement
measures and it is only in this way that viable limits of permissable
noise levels can be established. Further, such specified limits may be
used to assess the existing quality of an environment and can be adjusted
in time to lower values in order to provide the basis for a continuing
improvement in the environment. The Federal Government has taken such
action to set standards for the emission of noise from major sources under
the provisions of various legislative acts and through actions by different
regulatory agencies.
4.2.1 Historical Perspective
Regulation for the control of noise is not a recent societal
concern. Reportedly, there was an ordinance enacted some 2500 years
ago in ancient Sybaris, Greece, banning metal works and the keeping of
roosters within the city in order to protect against noise that would
interfere with speech and/or disturb sleepJ In the United States, how-
ever, the Federal Government as well as the general populace have been
generally unconcerned with the level of noise in the American environment
until recently.
Our concern over the increasing intrusion of noise in our environ-
ment closely follows that expressed by many European countries in the
post World War II era. Noise problems became evident in many European
countries during the period of reconstruction and economic expansion
following the war. The continuing construction and transportation related
noise have made substantial impact in the lives of many Europeans.
In the United States the urbanization of our society, the increased
mobility of our life style, and the technological advances of our industri-
alized society have been among those factors that have brought large
numbers of people into close contact with sources of noise. Many new
noise sources such as commercial aviation (the SST), recreational vehicles
(the snowmobile and motorcycle), mechanized tools (the gasoline-engine-
powered chainsaw and lawn mower), and convenience devises (appliances),
have entered our daily lives. The noise produced by these elements has
combined with that already existing in the environment and has resulted in
a general awareness of dissatisfaction with the noisy conditions which
pervade both our working and leisure environments.
See Reference 49, page 1-4.
4-2
-------
The increasing popular pressure for noise abatement has resulted
in a variety of activities in the public and private sectors. The
Federal Government has taken steps to increase and coordinate its activities
for the control of noise. Most importantly, it has assumed responsibility
for noise regulation of activities affecting interstate commerce (or the
national defense), an area where State and local governments cannot be
effective.
The Noise Control Act of 1972 (2) was adopted as U.S. public law to
control the emission of noise that is detrimental to the human environment.
It is based on the findings of the U.S. Congress which state the "inadequately
controlled noise presents a growing danger to the health and welfare of the
Nation's population, particularly in urban areas." Also, the Act serves
to provide a national uniformity in the control of major sources of noise
in commerce while at the same time recognizing that the primary responsi-
bility for control of noise rests with State and local governments. The
Act embodies a policy that calls for the promotion of an environment
for all Americans that is free from noise that jeopardizes health or welfare.
To date, the Noise Control Act of 1972 remains as one of the primary
motivating forces behind the national collective movement for quieting
the environment. The act was the culmination of effort's begun when the
Office of Noise Abatement and Control (ONAC) was established within the
U.S. Environmental Protection Agency (EPA) by authority of the Noise
Pollution and Abatement Act of 1970. This Act required that the ONAC
conduct a full and complete study of noise and its effects on the public
health and welfare and report the results, together with EPA's recommenda-
tion for legislation, to the President and Congress. The report (3) was
published in 1972, having been prepared on the basis of material collected
and published in 15 technical information documents (4-18) and from
testimony obtained at eight different public hearings held by the ONAC (19-26),
4.2.2 Occupational Noise
A very substantial effort by the Federal Government to regulate and
control exposure of people to noise has arisen in the area of occupational
health and safety. In May of 1969, under provisions of the longstanding
Walsh-Healy Public Contracts Act of 1942, the U.S. Secretary of Labor issued
regulations (27) requiring the administration of a continuing, effective
hearing conservation program. Noise exposure limits were established in
terms of permissable level and duration of exposure. This established the
now widely known permissable limit of 90 dB(A) sound level for an 8-hour
duration in the work place which is estimated to protect about 85% of the
working population from adverse hearing impairment during a normal working
lifetime. The Walsh-Healy criteria were restricted in that they were
applicable only to working conditions of employees of contractors supplying
the Federal Government with materials, supplies, articles, or equipment
under contracts in excess of a total amount of $10,000.
4-3
-------
The Williams-Steiger Occupational Safety and Health Act of 19702
(PL 91-596) (28) became effective April 28, 1971, and authorized the U.S.
Secretary of Labor to set mandatory occupational safety and health standards
applicable to businesses affecting interstate commerce. On May 29, 1971,
(29) under the provisions of this Act, the Secretary extended the Walsh-
Healy standards for noise exposure to apply to all businesses affecting
interstate commerce. This action was meaningful in that substantial
numbers of employees were included under this Act and penalties were
specified that involved civil and criminal actions against violators of
the law in order to ensure compliance by employers. Activity under this
Act by the Occupational Safety and Health Administration (OSHA) of the
U.S. Department of Labor has received considerable public attention since
OSHA was created in 1970. OSHA published a new set of proposed require-
ments and procedures for control of occupation noise exposure on October
24, 1974 (30). These standards have received wide-ranging comment and
some criticism due, in part, to the fact that they would maintain the
prevailing limits of exposure such as 90 dB(A) for 8 hours. In fact,
others would have proposed lower exposure limits. In general, all of the
interested parties concur that limits lower than those proposed in the
new OSHA requirements are a desirable goal, but there are differences in
opinion about the costs and practicality of lower limits. There are also
differences in opinion about the noise control procedures to be used. For
instance, should the use of hearing protectors be endorsed as more than a
temporary means of reducing exposure? Is reduction of the noise at the
source by engineering control procedures too expensive or impractical?
It should be recognized at this point that enabling legislation such
as the Occupational Safety and Health Act of 1970 or the Noise Control
Act of 1972 generally provides the authority for setting criteria, and that
subsequent regulations or standards are promulgated by the appropriate
administrative body (OSHA or ONAC) in compliance with the general provisions
of the legislation. It is in this context that, frequently, our courts
and judicial system come into play in order to provide an interpretation
of the legislative intent as regards its proper (and legal) administration.
4.2.3 Aircraft/Airport Noise
Aviation noise abatement is one of the most regulated areas of
environmental noise at the Federal level. This has been due to a combina-
tion of factors. There has been the rapid development of the technology
of flight in the post-World War II years and the resultant introduction
of increased numbers and types of aircraft (the jet airliner) which are
major sources of noise in the environment. Further, there has been the
necessity for the Federal Government to exercise a preemptive responsibi-
lity for controlling this segment of interstate commerce. It was in 1968
when Public Law 90-411 (31) added Section 1431 titled "Control and Abate-
ment of Aircraft Noise and Sonic Boom: to the Federal Aviation Act of 1958
and the Department of Transportation Act of 1966. Under the legislative
2
Sometimes referred to as the OSHAct (of 1970).
4-4
-------
authority of this Act, the Federal Aviation Administration (FAA) of the
U.S. Department of Transportation promulgated Federal Aviation Regulations
(FAR) Part 36 (32) to put a stop on the escalation of aircraft noise. These
regulations set noise emission standards to be used in type certification
procedures that are applied to new aircraft types or existing types on
which "acoustical changes" are to be made. Unfortunately, these regulations
were adopted too late to be effective for the majority of types of airplanes
that will be in our commercial fleet until well after 1980. That is, pre-
wide-body jets.such as the Boeing 707-320 B/C, 727, 737, and DC-9 are not
covered unless "acoustical changes" are made. (The Boeing 747 was at the
stages of final development at the time these regulations were enacted and
a time period was given for them to meet the FAR Part 36 noise level require-
ments.) However, subsequently the EPA and FAA have developed other regula-
tions that require a program of retrofit and replacement of existing
commercial airplanes in order that they also meet existing Federal (FAR
Part 36) noise standards (33). This retrofit program has been developed
in accordance with a phased time schedule designed to be completed on
January 1, 1985. This action clarifies the overall aims of a high-priority
program for noise abatement of aircraft noise and assures a better measure
of program success.
The FAA is also initiating noise control regulations and guidelines
in such areas as the control of operational (flight) activities,:; and
airport planning for development and/or improvements of facilities. The
highest standards for aviation safety are included in all of these noise
abatement activities since the FAA has the authority and responsibility
for both of these problem areas.
The EPA has a special role in the area of aircraft/airport noise
under the Noise Control Act of 1970, whereby the agency is required to
make proposals to the FAA with regard to any regulations that may be
required to protect the public health and welfare. The FAA must then
respond by either agreeing to the proposal or explaining its disagreement.
Thus, the FAA may choose to either promulgate or disregard EPA-suggested
regulations.
4.2.4 Surface Transportation Noise (Highway and Railroad)
In 1966, the U.S. Congress passed the Department of Transportation
Act which created the U.S. Department of Transportation (DOT). Under
this Act the Secretary of the DOT is directed to ". . . promote and
undertake research and development relating to transportation, including
noise abatement with particular attention to aircraft noise ..." Progress
in the area of rules and regulations to control and abate highway noise
has occurred since that time. A 1970 Amendment (P.L. 91-605) to the
Federal-Aid Highways' Act requires the Secretary to develop and promulgate
standards for highway noise levels that are compatible with different land
uses. The Act further specifies that approval for Federal aid not be
given for any proposed project unless the standards for noise levels are
met. Such standards for abatement of noise from highways and highway con-
struction were first issued in April 1972 by the Federal Highway Administra-
tion (FHWA) of the DOT as Policy and Procedure Memorandum (PPM) 90-2
4-5
-------
(34). Subsequently, standards and procedures rules were issued and became
effective May 24, 1976 (35). These rules include a non-retroactivity
provision which means that prior approval actions initiated in conformance
with PPM 90-2 are not preempted. These newer noise standards set forth
provisions for highway-traffic noise studies, noise abatement procedures,
steps for coordination with local officials, and desired noise levels
for use in the planning and design of highways which are to be approved
for development persuant to Title 23, United States Code. In support of
efforts to abate highway noise, the ONAC of the EPA has taken steps to
regulate sources of highway noise. On October 29, 1974, under authority
of the Noise Control Act of 1972, the EPA issued regulations (36) setting
specific maximum in-use noise emission standards applicable to vehicles
weighing over 4,536 kg (10,000 pounds) Gross Vehicle Weight Rating (GVWR)
that are operated by interstate motor carriers. To be effective as of
October 14, 1975, these standards set maximum limits for stationary and
moving operations such as: 88 dB(A) measured at 50 feet for a stationary
run-up(or acceleration) of the engine from idle to governed speed with
wide-open throttles. In addition, these standards require that vehicle
exhaust systems not be defective and ban the use of noisy tires on
vehicles subject to the regulation. Rules prescribing procedures for
inspection, surveillance and measurement of motor vehicles to determine
compliance with these standards have been promulgated by the Bureau of
Motor Carrier Safety (BMCS) of the DOT (37). BMCS is responsible for
enforcement of these regulations. In addition to this in-use regulation
of noise emission from heavy trucks, the EPA has promulgated noise emission
standards for new medium and heavy duty trucks (38). These standards will
become effective on January 1, 1978, and include a provision for the
subsequent lowering of maximum limits which will become effective in 1982
and 1985. These new product standards which are to be enforced by EPA
are more stringent than the in-use regulations. They are the result of
the EPA's earlier work in identifying trucks among the transportation
products which are major sources of noise (39). (Other products similarly
identified as major sources of noise are to be similarly covered by new-
product noise emission standards.) In the case of the in-use truck noise
emission standards, several States and localities have joined with the
BMCS in enforcing these regulations and this i's a pertinent example of
the type of cooperation that should be encouraged between different
governmental jurisdictions for quieting the environment.
In the area of railroad noise, the EPA has promulgated railroad.
noise emission standards establishing specific maximum in-use noise
level standards applicable to trains operated by interstate rail carriers
(40). These standards which became effective on December 31, 1976, are
for measurements made at 100 feet perpendicular to the center line of
the truck and they include more restrictive levels for locomotives
manufactured after December 31, 1976. The DOT through the Federal Rail-
road Administration (FRA) is responsible for the enforcement of this
regulation and has issued compliance regulations for enforcement of the
emission standards (41). Under a provision of these regulations, any State
or local jurisdiction may arrange to enforce the emission standards.
4-6
-------
4.2.5 Neighborhood Noise
Neighborhood noise is a broad classification, including various
types of noise sources and control measures. There are several Federal
requirements and standards that are applicable in this area. The
Public Buildings Service of the General Services Administration (GSA) has
issued noise control requirements for construction equipment These
requirements apply to work at sites of Federal Government structures
under contract with the GSA (42). In addition to specifying equipment
noise emission limits, these rules require contractors to comply with all
applicable State and local rules and regulations relative to noise control.
Of more importance and long range impact, however, are the standards
for noise abatement and control that have been issued by the U.S. Depart-
ment of Housing and Urban Development (HUD) in August, 1971 (43). HUD
has adopted a program policy for noise abatement and control that includes
consideration of housing site selection (external noise exposure standards),
structural characteristics of buildings (interior noise exposure stand-
ards), and noise ratings for appliances and equipment where the use of
quieter products might be encouraged through departmental policy. In
particular, HUD support is prohibited for new construction on sites that
have unacceptable noise exposures. The adoption of these standards means
that buildings to be financed with HUD's support will be constructed with
noise-exposure abatement as a primary consideration for the future occupants,
EPA is also directly involved in the abatement of neighborhood noise
through its actions to identify major sources of noise and promulgate
noise emission standards for products distributed in commerce. Among
those products that have been either identified or considered for identi-
fication as major sources of noise are portable air compressors, truck-
mounted solid waste compactors, motorcycles, power lawn mowers, pavement
breakers, chainsaws, and air conditioners. Regulatory action to set
noise emission standards for new products in these categories is one of
the most effective ways of addressing the neighborhood noise problem.
Controlling noise at the source is the most cost-effective method of re-
ducing noise and by requiring all manufacturers to meet comparable
standards, pressure is applied so that available technology will be
incorporated into new products.
4.3 State and Local Government
There has been an increase in State and local programs for nosie
control over the past years. However, in many communities, budget crises '
have restricted the growth of programs and in some cases have led to
their termination. Similarly, State programs have had to be tempered
because of cost considerations. It is not possible to cover the extent
or exact nature of these programs in any detail here because of the varia-
tions between programs and the large number of programs that exist. To
begin with, the number of State and local noise control programs has been
4-7
-------
estimated to have increased from 288 in 1973 to 665 in 1976 (44). In
December 1974, a report was given (45) that listed 440 municipalities
with noise regulations as compared to only 288 listed in the previous
year, December 1973 (46). These 440 ordinances in 1974 represented
provisions for noise control that were applicable to a combined population
in excess of 62 million people. However, the provisions were different
among ordinances in that the legal categories considered varied from
either nuisance, zoning, vehicle, aircraft, or building noise singly to
some combination of the five categories being covered by ordinance.
Some local ordinances may seek to control specific noises such
as lawnmower or construction-site noise by limiting the hours of the
noisy activity. Other laws may seek to provide comprehensive regulation
for noise in the community. Zoning ordinance requirements may be based
in part upon the goal of separating noise sources from certain segments
of the community. Building codes may be used to protect the public from
indoor noise in multi-family dwellings or from outdoor noise in housing
that is to be located in noisy areas. Incorporation of noise regulations
in existing codes requires that enforcement rest with the respective code
enforcement agency. In contrast, a more comprehensive noise abatement
program would better place regulation and enforcement with a special agency
and suitably trained personnel.
In many cases, legislation for noise abatement at the State
level made its appearance along with other legislation related to the
environment. Most of this legislation was limited to the establishment
of State environmental agencies or commissions, or to the delegation of
authority in the area of the environment to existing agencies. Responsi-
bility was given to set standards and guidelines concerning the control
and abatement of pollution in various forms. Such laws fall commonly into
three categories. They are either general environmental laws which
specifically includes noise as an environmental problem, laws dealing
only with noise, or environmental laws which make no mention of noise
but which could be used by the States to combat their noise problems.
Recently States as a group have become more sophisticated in the writing
of noise laws. States are beginning to specify noise limits in terms of
decibels instead of the subjective and inexact terms previously used,
such as "unnecessary" and "unreasonable." A growing number of States are
also setting standards for noise from new vehicles and equipment and
forbidding the sale of any such products that fail to conform to the
standards. However, a coordinated and consistent pattern of program
development between States has not yet evolved. Established programs
which are characterized by a high level of activity and appropriate
personnel, funding, instrumentation and enforcement activities are in
the minority. As of 1974, the majority of States had either no program
or minimal activities in noise control. A more recent report (47) given
in December 1977 cites that there are now in excess of 900 local, county
and State noise control laws, and that this represents nearly a 300%
increase in legislative activity since 1970.
4-8
-------
At the regional level, there are several examples of noise
abatement regulatory agencies. The most notable one is perhaps the Port
Authority of New York and New Jersey, a bi-state agency created by
the States of New York and New Jersey. This Authority has established
noise standards for the operation of the airports within its jurisdiction;
these include Kennedy, La Guardia, Newark, and Teterboro Airports in the
vicinity of New York City. The Authority is exempt from municipal and
State laws with the exception of bi-state amendmentof its charter. It
has set up regulations governing take-offs from its airfield using an
objective set of criteria for noise measured at cerain points in the
communities surrounding the airports. However, the only way the.Port
Authority can enforce these regulations is to threaten the withholding
of permission for planes to land. Unfortunately, there are frequent
jurisdictional conflicts when it comes to this type of regional noise
regulation and enforcement. This is understandable when one considers
that many (several dozen) Federal and State agencies are involved with
an airport facility. Other examples of regional efforts in noise abate-
ment are the Minneapolis-St. Paul regional zoning for airports as well
as a similar scheme for the Dallas-Fort Worth Regional Airport.
4.4 Progress Resulting from the Noise Control Act of 1972
In March 1977, EPA reported (48) on the progress it had made
in accomplishing the mandated requirements of the Noise Control Act of
1972. As has already been mentioned, this Act sets as its goal the
promotion of an environment for all Americans free from noise that
jeopardized their health and welfare. Various sections of the Act contain
requirements for definite outputs or major coordinating actions by EPA.
Certain of these activities have already been discussed in the previous
section of this Chapter on the Federal Government under the different
categories of noise legislation, but it is instructive to consider briefly
the progress made under the 19 sections of the Noise Control Act. Sections
1 through 3 and 19 deal with the short title, Congressional findings and •
policy, definitions, and Congressional appropriations for the Act.
Section 4 of the Act requires: 1) each Federal agency to comply with
Federal, State, interstate, and local noise control requirements and
2) EPA to coordinate all Federal noise research and control programs.
There has been substantial progress in this area and the emergence of a
convergent trend in the actions of Federal agencies to implement the policy
of the Act, with a leadership role being undertaken by EPA. Under Section
5 of the Act, EPA is required to publish two major documents and this has
been done. First, the "Public Health and Welfare Criteria for Noise"
document (49) represents an appraisal of available knowledge relating to
the effects of noise on the public health and welfare. The second
document published in 1974 (50) identifies levels of environmental noise
requisite to-protect the public health and welfare with an adequate margin
of safety. A further requirement of this section is for EPA to identify
products which are major sources of noise. Through February 1977, EPA
has identified ten such products as:
4-9
-------
Portable air compressors
Medium and heavy trucks
Wheel and crawler tractors (loaders and dozers)
Truck refrigerator units
Truck-mounted solid waste compactors
Motorcycles
Buses
Power lawn mowers
Pavement breakers
Rock drills.
Other products are under pre-identification study and may be anticipated
to join the listing.
Under the previsions contained in Section 6 of the Noise Control
Act, EPA is authorized to promulgate noise standards for any products
identified as major noise sources (per reports published under section 5)
or for products for which standards are considered both feasible and
necessary. These noise emission regulations shall contain performance
standards which are the result of careful consideration of many factors
including the cost of compliance. Given such standards, manufacturers
shall warrant that products are designed, built, and equipped so as to
conform at the time of sale with applicable regulations. The EPA has
published final regulations on newly manufactured protable air compressors
and for medium and heavy trucks (both regulations are effective in 1978).
Proposed standards for other products are included in the ongoing regula-
tory program of EPA. A Noise Enforcement Division of the EPA has been
established with responsibilities that include covering the manufacture
of new products having noise emission standards. It is important to note
that provisions of Section 6 include a prohibition that: no State
or political subdivision thereof may. adopt or enforce noise emission
standards for new products that are not identical to those published by
EPA. However, nothing shall preclude the rights of these same political
jurisdictions to establish and enforce controls on environmental noise
through the licensing, regulation, or restriction of the use, operation,
or movement of any product or combination of products.
Section 7 of the Act covers aircraft noise standards in a special
way. It first directs EPA to study the adequacy of aircraft noise controls
and standards and report their findings to Congress. This has been done (51)
The remainder of the Section is actually an amendment of the Federal
Aviation Act of 1958 which has been referred to in the previous discussion
of aircraft/airport noise. Aviation noise regulatory authority is given
to the FAA, with EPA playing a significant role in the process by way
of submitting proposed rules to the FAA.
Section 8 of the Act gives EPA authority to designate products which
either may emit adverse kinds of noise or are sold on the basis of reducing
noise. For these products, EPA shall require appropriate labeling so as
to provide notice to the prospective user concerning the level of noise
emitted or, the effectiveness of the product for reducing noise. Here
again, States or political subdivisions thereof are not prevented from
similar product labeling regulations so long as they do not conflict with
EPA regulations.
4-10
-------
In Sections 9 through 13 of the Act, further authority is assigned
to agencies and provisions are made as follows. The Secretary of the
Treasury issues regulations for new products to be imported into the
country (Section 9). Prohibited acts are spelled out in Section 10 with
regards to the new products and labeling requirements under sections 6
and 8; and Section 11 provides for enforcement with specified penalty
against such prohibited acts. In Section 12, provisions are made for
citizen suits to prevent and/or correct violations of the noise control
requirements, standards, rules, or regulations contained or issued
under provisions of the Act itself. EPA is given authority to require
records, reports, and information from manufacturers in Section 13 of
the Act. This material would be for products to which emission or
labeling regulations apply under Section 6 or 8 of the Act.
Section 14 on research, technical assistance, and public information
provides EPA with certain authority to: (a) conduct and finance research,
(b) advise on training of noise control personnel and on selection and
operation of noise abatement equipment as part of technical assistance
to State and local governments, (c) develop improved methods of
measuring and monitoring noise (in cooperation with the National Bureau
of Standards), (d) prepare model State or local legislation for noise
control, and (e) disseminate information to the public. The many
activities of EPA in this regard are substantial and have been summarized
in their progress report (48).
Section 15 of the Act provides for development of procedures to
certify products as "low-noise emission" products if they emit noise in
amounts significantly below the levels specified in noise emission
standards promulgated under Section 6 of the Act. As such, these products
would be subject to special rules and cost allowances for their procure-
ment by the Federal Government. In Section 16, procedures are spelled
out for judicial review of the actions taken by EPA under certain sections
of the Act (promulgating standards, regulations and labeling requirements),
In Sections 17 and 18 of the Act, provisions for regulation of
railroad and motor carrier noise emission standards are given. As has
been discussed previously, these regulations require the EPA to promul-
gate noise emission standards and for the DOT to issue compliance
(enforcement) regulations. In both cases, this has been institued. Two
provisions of each of these sections are of interest in that State or
political subdivisions thereof may 1) neither adopt nor enforce any
noise emission standards which are not identical with ones that .have
already been promulgated by EPA under these sections, and 2) have the
right to establish and enforce standards or controls on levels of
environmental noise, and/or otherwise control license, regulate, or
restrict the use, operation, or movement of any related product if, the
EPA and DOT concur that such program is necessitated by special local
conditions and is not in conflict with Federal regulations. Once again
we have an example of how the Noise Control Act contains provisions which
recognize the rights of State and local governments to regulate and
control noise, and spells out the basis for a coordination between
governmental programs at different levels.
4-11
-------
4.5 Roles and Authority - Toward a National Strategy for Noise Control
In April of 1977, EPA published the 62 page document "Toward a
National Strategy for Noise Control" (44). This document was developed
"to continue the dialogue on the overall goals of the noise program, the
role of government, the role of consumers, and the role of industry in
noise control, along with the selection of specific abatement and enforce-
ment activities for EPA". To reach the Noise Control Act's primary objec-
tive of a noise-free environment, EPA has formulated five specific opera-
tional goals for the future. These goals are:
A) To take all practical steps to eliminate hearing loss
resulting from noise exposure;
B) To reduce environmental noise exposure to an L. value
of no more than 75 dB immediately;
C) To reduce noise exposure levels to Ldn 65 dB or lower by
vigorous regulatory and planning actions;
D) To strive for an eventual reduction of noise to an L.
of 55 dB; and
E) To encourage and assist other Federal, State and local
agencies in the adoption and implementation of long range
noise control policies.
These goals are intended to be part of the basis for a national program.
In assessing the existing status for developing a more unified and
coordinated approach to a national program, EPA has established the follow-
ing. In the first years of activity since passage of the Noise Control
Act, EPA has been of necessity mostly concerned and occupied with meeting
certain specified deadlines for mandatory documents such as the airport/
aircraft report, and the criteria and environmental noise level documents.
(49-51). Secondly, EPA has placed top priority on attacking the most
serious noise sources first and therefore has developed source standards
and regulations in the surface transportation and construction areas.
Where lower priority has previously prevailed - in the areas of technical
assistance, Federal program coordination, and labeling -- EPA now finds
itself in a position to increase its activity and provide the support for
a broader approach to national noise control. They have identified three
specific components that will greatly influence the shape of a national
program according to the emphasis used. These are: (a) Federal noise
emission regulations for new products, (b) State and local controls, and
(c) Federal regulations requiring the label.ing of products. Accordingly,
EPA has designed a plan for their own program of activities with the inten-
tion of maximizing the effectiveness of their authority and influence
effectively. This strategy recognizes the essentiality of (a) State and
local programs, (b) other Federal programs, and (c) informed consumer
choice (through product labeling), for the national noise control effort.
A major area of emphasis will be in the expansion of assistance to State
and local agencies. This is considered essential to provide more immediate
relief from noise, to provide control of non-federally regulated sources of
noise which are either a "nuisance" or otherwise a component of neighborhood
noise, and to assist in the enforcement of EPA standards.
4-12
-------
The EPA has only a portion of the authority necessary to carry out
a national noise abatement and control effort. However, the Noise
Control Act of 1972 has given the Agency the responsibility to serve as
the coordinator of all Federal government noise abatement activities and,
to give technical assistance 'to State and local agencies and to the general
public. Unlike other Federal environmental legislation, the Act places
no specific requirements upon State and local governments. Rather,
full discretion is left to these governments as to whether to become
involved in noise control, and as to what degree. In addition, there
are no provisions for grants to help fund local programs. The permitted
delivery of technical assistance by the Federal Government is an activity
that will require extensive utilization of the limited manpower resources
which EPA has to offer. With the increase in the number of communities
that are initiating noise programs, and the need to solve the practical
problems of actual implementation and enforcement, EPA has designed a
new approach to the delivery of noise control technical assistance to
State and local governments.
The new approach is composed of two related programs: the Quiet
Communities Program (QCP) and the ECHO (Each Community Helps Others)
Program. The QCP plans to select a number of communities around the
country and establish an intensive and close working relationship
between these communities and EPA's cognizant Regional Offices in
the development of a noise control program. These community programs
may be of various types, either comprehensive, or ones in some particular
functional area, such as construction site noise, motor vehicle noise,
boundary line standards, or railroad noise. Evaluations of these test
projects will serve as guides for the future efforts of other communities.
Under the ECHO program, EPA will assist communities, that have well-
developed and successful noise programs, to provide direct, person-to-
person technical assistance to other communities with similar problems.
In the following chapter, on tools for noise control programs,
further additional background information on rules and regulations
will be found. However, the interested individual is referred to the
EPA's national strategy document of April 1977 (44) and news of its
subsequent further development for additional details.
4-13
-------
References
Many of the following documents can be purchased through the U.S.
Government Printing Office (GPO), Washington, D.C. 20402, Phone 202/
783-3238 or the National Technical Information Service (NTIS), U.S.
Department of Commerce, 425 13th St., N.W., Room 620, Washington, D.C.
20004, Phone 202/296-4348. A GPO or NTIS document number will be
'included with the reference in such cases.
1. Bugliarello, G., Alexandre, A., Barnes, J. and Wakstein, C.,
The Impact of Noise Pollution, A Socio-Technological Introduction,
Pergamon Press Inc., Maxwell House, Fairview Park, Elmsford, NY
10523, 1976.
2. Noise Control Act of 1972, Public Law 92-574, 92nd Congress, H.R.
11021, October 27, 1972, 86 Stat. 1234.
3. "Report to the President and Congress on Noise," U.S. Environmental
Protection Agency, Office of Noise Abatement and Control, Washington,
D.C. 20460, EPA Document No. NRC 500.1, December 31, 1971. (GPO
Stock No. 5500-0040) (NTIS No. PB-206-716).
4. "Noise from Construction Equipment and Operations, Building
Equipment, and Home Appliances " NTID 300.1, U.S. Environmental
Protection Agency, Office of Noise Abatement and Control, Technical
Document, December 1971. (GPO Stock No. 5500-0044) (NTIS No. PB-
206-717).
5. "Noise from Industrial Plants," NTID 300.2, U.S. Environmental
Protection Agency, Office of Noise Abatement and Control, Technical
Document, December 1971. (GPO Stock No. 5500-0042) (NTIS No. PB-
206-718).
6. "Community Noise," NTID 300.3, U.S. Environmental Protection
Agency, Office of Noise Abatement and Control, Technical Document,
December 1971. (GPO Stock No. 5500-0041) (NTIS No. PB-207-124).
7. "Laws and Regulatory Schemes for Noise Abatement," NTID 300.4,
U.S. Environmental Protection Agency, Office of Noise Abatement
and Control, Technical Document, December 1971. (GPO Stock No.
5500-0046) (NTIS No. PB-206-719).
8. "Effects of Noise on Wildlife and Other Animals," NTID 300.4,
U.S. Environmental Protection Agency, Office of Noise Abatement
and Control, Technical Document, December 1971. (GPO Stock No.
5500-0055) (NTIS No. PB-206-720).
4-14
-------
9. "An Assessment of Noise Concern in Other Nations," (2 Vols.) NTID
300.6, U.S. Environmental Protection Agency, Office of Noise
Abatement and Control, Technical Document, December 1971. (GPO
Stock No. 5500-0043) (NTIS No. PB-206-721, Vol.1 and PB-206-722 Vol.2),
10. "Effects of Noise on People," NTID 300.7, U.S. Environmental
Protection Agency, Office of Noise Abatement and Control,
Technical Document, December 1971. (GPO Stock No. 5500-0050)
(NTIS No. PB-206-723).
11. "State and Municipal Non-Occupational Noise Programs," NTID 300.7,
U.S. Environmental Protection Agency, Office of Noise Abatement
and Control, Technical Document, December 1971. (Available at
NTIS only, NTIS No. PB-208-659).
12. "Noise Programs of Professional/Industrial Organizations, Universities
and Colleges," NTID 300.9, U.S. Environmental Protection Agency,
Office of Noise Abatement and Control Technical Document, December
1971. (GPO Stock No. 5500-0053) (NTIS No. PB-207-125).
13. "Summary of Noise Programs in the Federal Government," NTID 300.10,
U.S. Environmental Protection Agency, Office of Noise Abatement
and Control, Technical Document, December 1971. (GPO Stock No.
5500-0061).
14. "The Social Impact of Noise," NTID 300.11, U.S. Environmental
Protection Agency, Office of Noise Abatement and Control, Technical
Document, December 1971. (GPO Stock No. 5500-0047) (NTIS No. PB-
206-724).
15. "The Effect of Sonic Boom and Similar Impulsive Noise on Structures,"
NTID 300.12, U.S. Environmental Protections Agency, Office of Noise
Abatement and Control, Technical Document, December 1971. (GPO
Stock No. 5500-0048) (NTIS No. PB-206-725).
16. "Transportation Noise and Noise from Equipment Powered by Internal
Combustion Engines," NTID 300.13, U.S. Environmental Protection
Agency, Office of Noise Abatement and Control, Technical Document,
December 1971. (GPO Stock No. 5500-0045) (NTIS No. PB-208-660).
17. "Economic Impact of Noise," NTID 300.14, U.S. Environmental Protection
Agency, Office of Noise Abatement and Control, Technical Document,
December 1971. (GPO Stock No. 5500-0049) (NTIS No. PB-206-726).
18. "Fundamentals of Noise; .Measurement, Rating Schemes, and Standards,"
NTID 300.15, U.S. Environmental Protection Agency, Office of Noise
Abatement and Control, Technical Document, December 1971. (GPO Stock
No. 5500-0054) (NTIS No. PB-206-727).
4-15
-------
19. "Public Hearings on Noise Abatement and Control," Vol. I -
Construction Noise - Atlanta, Georgia, July 8-9, 1971. (GPO
Stock No. 5500-0037) (NTIS No. PB-230-064).
20. "Public Hearings on Noise Abatement and Control," Vol. II -
Manufacturing and Transportation Noise (Highway and Air) -
Chicago, Illinois, July 28-29, 1971. (GPO Stock No. 5500-0085).
21. "Public Hearings on Noise Abatement and Control," Vol. Ill -
Urban Planning, Architectural Design; and Noise in the Home -
Dallas, Texas, August 18-19, 1971 / (GPO Stock No. 5500-0062)
(NTIS No. PB-230-065).
22. "Public Hearings on Noise Abatement and Control," Vol. IV -
Standards and Measurements Methods, Legislation and Enforcement
Problems - San Francisco, California, September 27-29, 1971.
(GPO Stock No. 5500-0036).
23. "Public Hearings on Noise Abatement and Control," Vol. V -
Agricultural and Recreational Use Noise - Denver, Colorado,
September 30 - October 1, 1971. (Available only at EPA).
24. "Public Hearings on Noise Abatement and Control," Vol. VI -
Transportation Noise (rail and other); Urban Noise Problems
and Social Behavior - New York, NY, October 21-22, 1971.
(GPO Stock No. 5500-0038).
25. "Public Hearings on Noise Abatement and Control," Vol. VII -
Physiological and Psychological Effects - Boston, Mass. October
28-29, 1971. (GPO Stock No. 5500-0056).
26. "Public Hearings on Noise Abatement and Control," Vol VIII -
Technology and Economics of Noise Control; National Programs and
their Relation with State and Local - Washington, D.C. November
9-12, 1971. (GPO Stock No. 5500-0095).
27. Safety and Health Standards for Federal Supply Contracts (Walsh-
Healy Public Contracts Act), U.S. Department of Labor, Federal
Register 34, 7948-49 (May 20, 1969).
28. Occupational Safety and Health Act of 1970, Public Law 91-596,
91st Congress, S. 2193, December 29, 1970, 84 Stat. 1590.
29. Occupational Safety and Health Standards (Williams-Steiger
Occupational Safety and Health Act of 1970), U.S. Department of
Labor, Federal Register, 36^10518 (May 29, 1971).
30. Occupational Noise Exposure, Proposed Requirements and Procedures
(Williams-Steiger Occupational Safety and Health Act of 1970), .
U.S. Department of Labor, Federal Register, 37773-37778 (October
24, 1974).
4-16
-------
31. An Act to Require Aircraft Noise Abatement Regulation, Public
Law 90-411, 90th Congress, H.R. 3400, July 21, 1968.
32. "Federal Aviation Administration Noise Standards," Title 14,
Code of Federal Regulations, Chapter I, Part 36.
33. "Federal Aviation Administration Regulations," Title 14,
Code of Federal Regulations, Chapter I, Subchapter F, Part 91.
34. "Federal Highway Administration Noise Standards and Procedures,"
Policy and Procedure Memorandum 90-2, February 8, 1973.
35. "Federal Highway Administration Highway Noise Control Standards
and Procedures," Title 23, Code of Federal Regulations, Chapter I,
Subchapter J, Part 772.
36. "Environmental Protection Agency Final Noise Emission Standards
for Motor Carriers Engaged in Interstate Commerce," Title 40,
Code of Federal Regulations, Chapter I, Part 202. (Federal
Register 39, 38208, October 29, 1974).
37. "Bureau of Motor Carrier Safety Regulations for Enforcement of
Motor Carrier Noise Emission Standards, Title 49, Code of Federal
Regulations, Chapter II, Part 325.
38. "Environmental Protection Agency Noise Emission Standards for
New Medium and Heavy Duty Trucks," Title 40, Code of Federal
Regulations, Chapter I, Part 205.
39. "Identification of Products as Major Sources of Noise,"
Environmental Protection Agency, Publication of Report,
Federal Register 39_, 22297, June 21, 1974.
40. "Environmental Protection Agency Railroad Noise Emission Standards,"
Title 40, Code of Federal Regulations, Chapter I, Part 201.
(Federal Register 41_, 2184, January 14, 1976).
41. "Federal Railroad Administration Railroad Noise Emission Compliance
Regulations," Title 49, Code of Federal Regulations, Chapter II,
Part 210, (Federal Register 42_, 42343, August 23, 1977).
42. General Services Administration, Public Buildings Service,
Construction Equipment and Practices, Noise Control, (Par.
44.8 in Guide Specification PBS 4-01100, October 1973).
43. "Noise Abatement and Control; Departmental Policy, Implementation
Responsibilities and Standards," August 4, 1971, Department of
Housing and Urban Development Circular 1390.2.
44. "Toward a National Strategy for Noise Control," U.S. Environmental
Protection Agency, Office of Noise Abatement and Control, Washington,
D.C. 20460, April 1977.
4-17
-------
45. Bragdon, C.R., "Municipal Noise Ordinances: 1974", Sound and
Vibration 8. 28-30 December, 1974.
46. Bragdon, C.R., "City Noise Ordinances - A Status Report," Sound
and Vibration 7. 34-35, December, 1973.
47. Bragdon, C.R., "Environmental Control Programs in the United
States," Sound and Vibration 11, 12-16, December, 1977.
48. "EPA Noise Control Program Progress to Date," U.S. Environmental
Protection Agency, Office of Noise Abatement and Control (AW 471),
Washington, D.C. 20460, March 1977.
49. "Public Health and Welfare Criteria for Noise," U.S. Environmental
Protection Agency, Office of Noise Abatement and Control, Washington,
D.C. 20460, EPA Document No. 550/9-73-002, July 27, 1973. (6PO Stock
No. 5500-00103) NTIS No. PB-241 000/AS).
50. "Information on Levels of Environmental Noise Requisite to Protect
Public Health and Welfare with an Adequate Margin of Safety," U.S.
Environmental Protection Agency, Office of Noise Abatement and
Control, Washington, D.C. 20460, EPA Document No. 550/9-74-004,
March 1974. (NtlS No. PB-239 429/AS).
51. "Report on Aircraft-Airport Noise," U.S. Environmental Protection
Agency, Office of Noise Abatement and Control, Washington, D.C.
20460, EPA Document No. Senate 93-8, August, 1973. (GPO Stock
No. 5270-01936).
4-18
-------
Chapter 5
NOISE ABATEMENT TOOLS
In terms of community noise control programs, the term "tool" must
be broadly defined to include anything that may be utilized by a community
as a means of aiding in the process of noise abatement. Thus, many tools
are available to communities including such varied things as texts,
reports, documents, legislation, services, equipment, and organizations.
It is not possible to list all tools that may prove beneficial to every
community noise control program because individual programs will vary
substantially in terms of factors such as type of noise source,
personnel background, and program resources. However, there are a
number of basic tools which are of fundamental importance to the develop-
ment and maintenance of effective community noise programs. These will
be discussed in this chapter under the various sectional groupings that
follow. It should be recognized that new tools are continually being
developed. Noise program personnel should consider incorporating these
new tools into their program as they become available.
5.1 General Background Information
5.1.1 Noise Control Act of 1972 (1)
This Act, United States Public Law 92-574, provides much of the
basis for the scope and direction of noise abatement activities through-
out the country at every level of public and private involvement. It
sets as its goal the promotion of an environment for all Americans free
from noise that jeopardizes their health and welfare. The Act mandates
the U.S. Environmental Protection Agency to undertake major coordinating
actions for a comprehensive national noise abatement effort.
5.1.2 Report to the President and Congress on Noise (2)
Prepared by the EPA in compliance with the Clean Air Act of 1970,
this report chronicles the earlier noise control efforts of EPA. The
report, submitted in 1972, was prepared from 1) a number of techno-
logical information documents prepared by EPA and outside contractors
and 2) testimony obtained at eight public hearings held throughout the
country. The Noise Control Act of 1972 (see 5.1.1) was originally intro-
duced as a proposed bill in this report.
The report contains 383 pages of textual material in six chapters
on the following topics:
1) Effects of Noise on Living Things and Property.
2) Sources of Noise and Their Current Environmental Impact
3) Control Technology and Estimates for the Future
4) Laws and Regulatory Schemes for Noise Abatement
5) Government, Industry, Professional and Voluntary
Association Programs
6) An Assessment of Noise Concern in Other Nations.
-------
As a resource document, this report provides a valuable consensus
of opinion regarding the effects of noise on public health and welfare
circa the early 1970's. It was also intended to aid State and local
governments and the general public in making decisions regarding the
enviornmental noise pollution problem.
5.1.3 Public Health and Welfare Criteria for Noise (3)
This document was developed and published by the EPA in accordance
with a requirement set forth in the Noise Control Act of 1972. The purpose
of this document was to "reflect the scientific knowledge most useful in
indicating the kind and extent of all identifiable effects of noise on
the public health and welfare which may be expected from differing
quantities and qualities of noise." The information presented, unlike
standards and regulations, does not take into account either feasibility
or cost of the control measures. Rather, the document was written to
provide a basis for the establishment of environmental noise level goals
(see Section 5.1.4).
The document contains twelve sections on the topics:
1) Noise and Noise Exposures in Relation to Public Health
and Welfare
2) Rating Schemes for Environmental Community Noise
3) Annoyance and Community Response
4) Normal Auditory Function
5) Noise-Induced Hearing Loss -- Temporary and Permanent
6) Masking and Speech Interference
7) Additional Physiological and Psychological Criteria
8) Effects of Noise on Performance
9) Interactions of Noise and Other Conditions or Influences
10) Effects of Infrasound and Ultrasound
11) Effects of Noise on Wildlife and Other Animals
12) Effects of Noise on Structures.
This document, which is frequently referred to as simply the
"criteria document", was published in July, 1973. In its preparation,
EPA sought to include the views and opinions of many of the leading experts
on the effects of noise. Towards that end, EPA'sponsored an International
Conference on Public Health Aspects of Noise in Dubrovnik, Yugoslavia
in May, 1973.1
Proceedings of the International Congress on Noise as a Public Health
Problem, Dubrovnik, Yugoslavia, May 13-18, 1973 are available as NTIS
Document No. PB-241 060/AS from the office of NTIS, 425 13th Street,
N.W., Room 620, Washington, D.C. 20004 (Phone 202/296-4348).
5-2
-------
5.1.4 Information on Levels of Environmental Noise Requisite to Protect
Public Health and Welfare with an Adequate Margin of Safety (47
Like the preceding "criteria document", this "levels document" was
also prepared by EPA in compliance with the Noise Control Act of 1972.
This Act required the publication of information on which to base goals
for environmental noise control programs. As in the preceding document,
neither cost nor feasibility have been considered in determining these
levels and therefore the EPA does not adopt them in their regulations
and standards. However, this document does present reasoned judgements
based on the best scientific work available. The levels presented in this
document are based on statistical determinations and incorporate a safety
margin. These statistical generalizations should not be applied to a
particular individual, and States and localities should approach this
information according to their individual needs and situations (see
Section 5.2.1, for instance).
Following an introductory Section, the report addresses the details
of characterizing and measuring human exposure to environmental noise
in Section II of the document. Section III summarizes cause and effect
relationships and presents them as the basis and justification for the
environmental noise levels that are identified in Section IV. These
levels for various indoor and outdoor areas in the public and private
domain are presented in terms of Leq and L^. Sections V and VI present
a list of references and are followed by several appendices containing
related material and information.
5.1.5 EPA Noise Control Program Progress to Date (5)
This 37 page booklet describes the progress made by EPA to date
(March 1977) in accomplishing the mandated requirements of the Noise
Control Act of 1972. This report also includes the EPA's plans for
future actions. The information is presented in a format that relates
the material to the appropriate sections of the Noise Control Act.
Listings of all available EPA noise-related publications and the names
and addresses of the EPA regional office Noise Representatives are also
included. This booklet is concise and informative. In particular, it
should prove useful to those persons interested in a coordinated national
program for a quieter America (see strategy document below).
5.1.6 Toward a National Strategy for Noise Control (6)
This document has been developed by EPA for their use in the comple-
tion of a comprehensive noise strategy. The Agency has sought public
comment in its preparation and intends to continue to seek public
participation and involvement as the strategy is shaped. The purpose of
the document is to present a report of the continuing dialogue on 1) the
overall goals of the noise program and 2) the roles of government, industry,
and consumers in noise control, along with the selection of specific
5-3
-------
abatement and enforcement activities for EPA. On the basis of the
directives of the Noise Control Act of 1972 and having completed its
first priority tasks, the Agency intends to broaden its approach to
national noise control It has designed a program intended to maximize
the effectiveness of its authority, as well as to encourage other parties
to use their authority effectively.
The document contains 53 pages of text in six sections of the
following topics:
1) Introduction - background and purpose
2) Nature and Scope of the Noise Problem -- effects and
prevasiveness of noise
3) Tools Available for the Control of Noise -- regulatory
measures
4) Goals for the National Effort -- general and specific
5) Relative Emphasis Among Alternative Approaches --
interrelationship of program components; national source
regulations and State and local programs; labeling
6) National Programs -- recommended programs; role of
research and development; cost and economic impact data;
source regulations; State and local programs; labeling;
awareness and public information; aircraft/airport noise;
enforcement; other Federal programs.
This strategy recognizes the essentiality of non-Agency endeavors
including State and local programs. As a result, EPA will be expanding
their assistance to State and local agencies and this strategy document
is of particular interest to a large audience of officials and interested
individuals.
5.2 State and Local Noise Control Legislation
5.2.1 Model Community Noise Control Ordinance (7)
This report contains a model ordinance for use by cities and counties
in the development of noise control ordinances tailored to meet local
conditions and goals. It is a comprehensive, performance-standard noise
ordinance intended to over-come enforcement problems associated with the
outmoded nuisance law approach to noise control. This report contains
sections on the control of noise from both stationary and mobile sources
and includes land use planning provisions. A preamble gives important
explanatory information for certain ordinance sections. This model
ordinance was prepared by the National Institute of Municipal Law
Officers in conjunction with the EPA. The model ordinance does not
contain recommended values for sound levels in the performance standards
because there were not any single numbers that could be chosen as
appropriate for all communities. Rather, localities are directed to.
consult the EPA "levels document" (see Section 5.1.4) for a specification
of national maximum noise exposure guidelines.
5-4
-------
5.2.2 Guidelines for Developing a Training Program in Noise Survey
Techniques (8)
This report contains guidelines for the content, format, organization,
and administration of a training program for noise survey technicians.
It is intended to provide assistance to State and local governments in
setting up a training program with the following objective: the training
of technicians to assist in the enforcement of noise ordinances and
investigation of noise complaints. The program is directed toward trainees
with a minimum of a high school education and no previous experience in
acoustics. The report outlines and explains material to be covered in a
4 1/2 day training program.
5.2.3 Chicago Urban Noise Study (9)
The city of Chicago has a noise ordinance that is one of the most
comprehensive and effectively enforced in the country. The basis for
this exemplary program is found in the document "Chicago Urban Noise Study"
which was submitted by Bolt Beranek and Newman Inc. In November, 1970
under contract to The City of Chicago. The document is actually a com-
pliation of three separate reports on four phases of the study. These
are:
Phase I. Noise in the Urban Environment
Phase II. Noise Control by Law
Phase III. Noise Control Technology and Federal Aid for
Noise Abatement
Phase IV. Noise Control Program Recommendation
The first report is on Phase I and draws from a review of the then current
literature to present material on needs for noise abatement and measure-
ment of urban noise. It describes the noise environment, discusses the
urban vibration environment, and provides a summary of existing noise
and vibration ordinances. In the second report on Phase II, a new noise
control ordinance is proposed along with relevant background and supple-
mentary material. The third and final report contained in the study
document presents results of the Phase III study on available noise
control technology and Federal assistance. In addition, a concise report
under Phase IV requirements is presented that gives seven recommendations
to improve Chicago's urban noise environment. This document is a valuable
reference that presents quite a comprehensive treatment of the urban noise
problem.
5.2.4 State and Municipal Noise Control Activities 1973-1974 (10)
This report presents an assessment of 1973-1974 State and
municipal environment noise control efforts based on an EPA survey of
1) States and 2) municipalities with populations greater than 75,000.
This assessment is designed to provide an overall perspective of the
composition and scope of noise control efforts. Areas covered are:
organization and orientation of noise control efforts, enforcement,
budgetary data, personnel, equipment, program problems, and application
of technical assistance.
5-5
-------
The survey results have been used by EPA/ONAC as a guide in the
present technical assistance program. This document has been prepared
primarily as a planning and reference guide for public administrators
and other officials engaged in the development and implementation of
environmental noise control programs. (Note: EPA has a continuing need
for information on State and local programs in order to develop an
integrated, nationwide noise control program that is to involve a
coordinated approach by the varying levels of government. Subsequent
surveys are planned that will include a larger number of communities).
5.2.5 Noise Source Regulation in State and Local Noise Ordinances (11)
This document in its most recent version (February, 1975) updates
the previous report by EPA on March .1, 1973. It has been prepared as a
planning and reference guide for public administrators of environmental
noise control programs. It presents a summary of noise source regulations
encompassed in current State laws and local ordinances. Data have been
extracted from only those laws and ordinances stipulating specific
decibel levels. For the States, the laws summarized are grouped under
the headings: motor vehicles, recreational vehicles, land use, and
general. For localities, the headings are: motor vehicles, recreational
vehicles, intrusive noise sources, stationary noise sources, construction
noise, and miscellaneous noise regulations. Because of the many variations
among local jurisdictional regulations, no attempt is made to list the
specific level requirements for recreational vehicles, construction equip-
ment, or land use.
5.3 Community Planning
5.3.1 Handbook for Regional Noise Programs (12)
This handbook is, intended as a working reference manual for EPA
regional program managers and staff personnel. Published in April,
1974, it provides a (then current) overview of the noise problem and
EPA's regional noise program. It was designed to be useful to non-
technical ly oriented and technically oriented personnel. This handbook
provides much valuable and important information through its straight-
forward format. It contains eleven sections, including areas on noise
effects, criteria for rating sounds, sources, measuring noise, and noise
reduction. Bibliographic references are provided throughout. The
appendices include a glossary of terms, a list of EPA noise documents,
a compilation of ordinances, and a schedule of EPA noise workshops.
5-6
-------
5.3.2 FAA Advisory Circular No. 150-5050-4 -- Citizen Participation in
Airport Planning (13)
This advisory circular is one of several that contain aviation noise
abatement information. These circulars have been prepared by the Federal
Aviation Administration (FAA) to present information of Agency policy.
Circular No. 150-5050-4 provides guidance for citizen involvement in
airport planning. It demonstrates the need for early citizen participa-
tion in airport planning and discusses methods by which this participation
may be achieved. Of particular note is the discussion of the off-airport
land use plan which is an element of an airport master plan and is designed
to achieve compatible land uses within areas affected by aircraft noise.
The affected citizen, professional planner, and elected official are
intended to be involved in the planning and decision making processes
for the long-range development of an airport and its neighbors in the
surrounding environment.
5.3.3 DOT Policy and Procedure Memorandum No. 90-2, Noise Standards
and Procedures (ITJ
The purpose of this memorandum is 1) to provide standards and
procedures for use by State highway agencies and the Federal Highway
Administration (FHWA) in the planning and design of highways approved.
pursuant to Title 23, United States Code, and 2) to assure that measures
are taken in the overall public interest to achieve highway noise levels
that are compatible with different land uses. Due consideration is also
given to other social, economic and environmental effects. Design noise
levels are specified in dB(A) with regard to land uses or activities at
the location of a proposed highway section. All projects to which noise
standards apply shall include noise abatement measures to obtain the
design noise levels in order to be leigible for Federal aid participation.
Noise abatement measures may include acquisition of property rights for
providing buffer zones, the installation of noise barriers, or, in some
specific cases, provision to "sound-proof" existing structures. More
recent highway noise standards and procedures are discussed in the FHWA
manual in the following section.
5.3.4 Federal Aid Highway Program Manual of Federal Highway Administration,
Volume 7, Chapter 7, Section 3 -- "Procedures for Abatement of
Highway Traffic Noise and Construction Noise" (15)
This directive is effective May 14, 1976 and promotes 1) policy
and procedures for noise studies and noise abatement measures, 2) design
noise levels, and 3) requirements for coordination with local officials
for use in the planning and design of highways approved pursuant to Title
23, United States Code. The requirements of this directive are not
retroactive and do not supersede prior approval actions such as those in
conformance with PPM 90-2 (see Section 5.3.3).
5-7
-------
5.3.5 Department of Housing and Urban Development Circular 1390.2,
Noise Abatement and Control (16)~
This circular presents HUD departmental policy. This policy 1) calls
attention to the adverse effects of noise exposure, 2) encourages the
control of noise at its source, 3) encourages land utilization that will
separate uncontrollable noise sources from residential and other noise-
sensitive areas, and 4) prohibits HUD support to new construction on
sites having unacceptable noise exposures. The circular presents further
explicit information on Departmental policy, implementation responsibilities,
and interim external and interior noise exposure standards for residential
construction.
5.4 Aircraft/Airport and Surface Transportation Noise Control, Abatement
and Enforcement
5.4.1 Report to Congress on Aircraft/Airport Noise (17)
This report was mandated under requirements of the Noise Control
Act of 1972 and was completed by EPA on July 27, 1973. The report
presents findings and recommendations in four major areas:
1) Adequacy of FAA flight and operational noise controls
2) Adequacy of noise emission standards on new and existing
aircraft, together with recommendations on the retro-
fitting and phaseout of existing aircraft
3) Implications of identifying and achieving levels of
cumulative noise exposure around airports
4) Additional measures available to airport operators and
local governments to control aircraft noise.
This report established the need for the submission of regulatory proposals
by EPA to the FAA. Activity in this regard has been undertaken and a
brief summary of the results appears in EPA's Noise Control Program
Progress booklet (pages 13 and 14) (5).
5.4.2 Transportation Noise and Its Control (18)
This 27 page booklet was issued by the Department of Transportation
in June, 1972. It is meant to serve as a primer on the problem of
transportation noise. Concise and well-illustrated, this booklet
presents information on transportation noise — what it is, how it differs
depending on sources and distance, and what can be done to curtail or
contain it. Included in the material covered are subsonic and supersonic
aircraft, highway noise, rapid transit noise, and appendices on measure-
ment of noise, propagation of sound, and residential noise level guide-
lines. (These latter guidelines are the ones presented in HUD circular
1390.2, see section 5.3.5).
5-8
-------
5.4.3 Department of Transportation, Bureau of Motor Carrier Safety
Regulations for Enforcement of Motor Carrier Noise Emission
Standards (T9)~
These compliance regulations prescribe procedures for enforcement
of the EPA in-use noise emission standards applicable to vehicles having
a Gross Vehicle Weight Rating of over 4,536 kg (10,000 Ib) that are
engaged in interstate commerce. Effective on October 15, 1975, these
regulations are enforceable by any special aqent of the FHWA or, under
provisions of the Noise Control Act of 1972, by States and localities
that have adopted identical standards.
5.4.4 Department of Transportation, Federal Railroad Administration
Railroad Noise Emission Compliance Regulations (20)
These compliance regulations prescribe procedures for enforcement
of the EPA in-use noise emission standards applicable to trains operated
by interstate rail carriers. The regulations are enforceable by Federal
Railroad Administration inspectors or by qualified persons designated
by any State or local jurisdiction that desires to undertake enforcement
and notifies the Administration.
5.5 Industrial/Occupational Noise Reduction
5.5.1 Criteria for a Recommended Standard . . . Occupational Exposure
to Noise (2TT
The Occupational Safety and Health Act of 1970 emphasized the need
for standards to protect the health of workers exposed to an ever
increasing number of potential hazards at their workplace, including that
of exposure to loud noise. The National Institute for Occupational
Safety and Health (NIOSH) of the U.S. Department of Health, Education,
and Welfare, Public Health Service, has projected a formal system of
research in order to provide relevant data from which valid criteria and
effective standards can be deduced. This NIOSH report, issued in 1972,
is a criteria document which presents recommendations for an occupational
exposure standard for noise. In addition, the report presents background
information, a discussion of acoustical terms and methods, a review of
the effects of noise on man, procedures for reducing noise exposure,
information on the development of the recommended standard, and a listing
of 139 references. Successive reports are intended as may be indicated
by the results from completed studies, in applicable areas of research
and development.
5-9
-------
5.5.2 NIOSH Industrial Noise Control Manual (22)
This manual was published in 1975 and contains fundamental informa-
tion to aid the user in understanding, measuring, and controlling indus-
trial noise. It was written for persons having little or no experience
in solving noise control problems, realizing that a large number of
businesses are not prepared to deal with their noise problems effectively.
There are seven chapters in the manual covering the following subjects:
1) Fundamental principles of sound
2) Noise measurement
3) Noise control techniques
4) Noise control materials
5) Case histories of successful applications of noise control
methods in actual industrial situations
6) How to choose a qualified consultant
7) References to additional pertinent literature.
The manual is designed to be used as a guide to help the reader develop
solutions to his/her particular noise problems using proven methods.
5.5.3 NIOSH Compendium of Materials for Noise Control (23)
This compendium of available, noise-reduction materials was developed
for use by plant engineers, industrial hygienists, acoustical consultants,
and others engaged in noise control. Published in June, 1975, it can be
used to determine the availability of noise control materials, the
characteristics, and specifications of the materials, and their supply
sources. Also included are data on both sound absorption and transmission
loss of materials and a general and technical description of the uses
and limitations of the materials listed.
5.5.4 Guidelines on Noise (24)
This medical research report was published by the American Petroleum
Institute in 1973. Developed to serve as a noise control manual, it
contains four sections that deal respectively with criteria regarding the
effects of noise on hearing, speech communication, and community response;
procedures for the measurement and evaluation of noise; precedures for
the reduction and control of noise; and current data related to noise
analysis and control. Together, these sections are intended to deal
effectively with all but the most specialized aspects of noise control
5.5.5 AIHA Industrial Noise Manual (25)
This third edition of the manual appeared in 1975. One of its
purposes is to present the available information that can provide
intelligent solutions to problems of noise control. In addition, it is
intended to serve as a resource tool for those responsible for establishing
5-10
-------
a complete hearing conservation program designed to prevent occupational
hearing loss in an industrial population. In logical order, this manual
presents the physics of sound; discusses noise measuring instruments and
noise analysis; surveys medical evaluation methods; examines the means
of noise control, both personal hearing protection and control of noise
at the source; and, finally, treats the legal aspects and liabilities in
detail.
5.6 Miscellaneous Handbooks, Periodicals, and References
5.6.1 Quieting: A Practical Guide to Noise Control (26)
This National Bureau of Standards (NBS) Handbook was issued in
July, 1976. It offers practical solutions for ordinary noise problems
that a person is likely to meet. The discussion describes the ways in
which sounds are generated, travel to the listener, and affect his hearing
and well-being. Recommendations are given for controlling noise at the
source and along its path of travel, and for protecting the listener.
The guide instructs the reader to heed "Warning Signs" to determine if
he is being subjected to prolonged noise exposure in the environment
that may be hazardous to his hearing. Remedies are presented for noise
problems encountered in the home, at work or school, while traveling and
in community development. These remedies include noise prevention
techniques and the selection of quiet alternatives to existing noise
sources. General principles for selecting quiet appliances are also
presented. Ways of searching for the sources of noise and for determining
the paths over which it travels are described. A detailed index is
given for individual noise sources describing specific solutions to the
problems they present. General ways of looking for quiet homes and travel
accommodations are described. In the final chapter, suggestions are given
for enlisting community help when large external noise sources, such as
those arising from public utilities and public transportation, must be
quieted.
5.6.2 Commercial Handbooks
There are many companies engaged in commercial activities related to
noise control. These firms publish a wealth of material on topics dealing
with noise abatement. In particular, there are two handbooks that may be
especially helpful. These are Application of B&K Equipment to Acoustic
Noise Measurement, 203 pages (27) and Handbook of Noise Measurement, 322
pages (28).Both of these noise measurement handbooks present a com-
prehensive treatment of the topic and present the fundamentals of noise
measurement and analysis.
5-11
-------
5.6.3 Periodicals
There is a large number of journals, newsletters and other publica-
tions that appear as periodicals and contain material related to noise
abatement and control. Among those that are devoted principally to this
area are:
1) Noise Control Report (29), a bi-weekly business newsletter
published in Washington, D.C. and available through
subscription,
2) Noise Regulation Reporter (30), a private subscription
information service that includes a reference file and
a bi-weekly publication report,
3) Noise/News (31), a bi-monthly newsletter published by the
Institute of Noise Control Engineering and dedicated to
the publication of new items related to the scientific
and engineering aspects of noise, its control, and its
effects on people,
4) Sound and Vibration (32), a monthly trade magazine sent at
no cost to persons concerned with noise and vibration control,
5) Noise Control Engineering (33), a professional journal
published bi-monthly by the Institute of Noise Control
Engineering in cooperation with the Acoustical Society
of America.
5.7 Standards
The object of standardization is to set up a set of rules that
facilitate the exchange of goods and/or services and develop mutual coopera-
tion in the spheres of intellectual, scientific, technological, and
economic activity. Standards in acoustics and mechanical shock and
vibration can be purchased from the American National Standards Institute
(ANSI), 1430 Broadway, New York, NY 10018. ANSI standards may also be
purchased from the Acoustical Society of America (ASA) along with other
ASA standards and an Index to Noise Standards -- ASA STDS. Index 1-1976
(national and international) (34). The source of standards varies among:
1) international organizations such as the International Organization for
Standardization (ISO) and the International Electrotechnical Commission
(IEC), 2) national organizations such as ANSI, ASA, and the American
Society for Testing and Materials (ASTM), 3) professional societies such
as the American Society of Heating, Refrigerating and Air-Conditioning
Engineers (ASHRAE) and the Society of Automotive Engineers (SAE), and
4) industry groups such as the Air Moving and Conditioning Association
(AMCA) and the National Electrical Manufacturers Association (NEMA). One
representative listing of standards and their sources may be found in
appendices material in the Handbook of Noise Measurement (28).
5.8 Environmental Protection Agency Services
The U.S. Environmental Protection Agency has a leadership role
in the task of environmental noise abatement. Their past activities
that have been reported in the Agency's "Progress to Date" booklet
5-12
-------
published in March, 1977 (5), and their planned future efforts will present
a vast array of noise abatement tools that may be used in State and local
programs. In the national strategy for noise control document (6), the
basis and outline for a cooperative and concerted effort by all segments
of the public and private sectors of the nation are presented. In recog-
nition of their roles, the technical assistance and public information
services of EPA will receive increasing attention and assume greater
importance in the Agency's ongoing program. Two components of this pro-
gram that may be singled out for their potential usefulness as tools for
State and local programs are listed in this final section of the chapter.
5.8.1 EPA Regional Offices
Assistance to State and local agencies is one of the major roles
provided by the ten EPA Regional Offices. These offices are assigned
responsibility for geographical areas throughout the country . Each
office has an individual designated as a noise representative. Efforts
are concentrated on encouraging the development of State and local noise
control programs to implement noise control benefits and to compliment
EPA regulatory efforts. EPA sponsored noise workshops are administered
by regional noise program personnel to train State and local officials
in all aspects of environmental noise. Through the Regional Offices,
sound level meters and other types of equipment are available for loan
to States and localities as well advice on types and uses of equipment.
Newer programs of EPA such as the Quiet Communities and ECHO programs
are designed to establish a more intensive and close working relationship
between the Regional Offices and these communities.
5.8.2 Noise Enforcement Division
This division was established in 1976 under the EPA 'Office of
Enforcement. This new Division's responsibilities include development
and implementation of enforcement regulations requiring testing, record
keeping, reporting and any necessary remedial actions by manufacturers
of new products for which standards of labeling requirements are prescribed
under the Noise Control Act. In addition, the Division will assist EPA
regions, States and localities in enforcing Federal noise control stand-
ards and regulations and in designing and enforcing supplementary State
and local controls. Under this Division a Noise Enforcement Facility,
located in Sandusky, Ohio, has been set up. In addition to laboratory
testing, this facility has mobile units that may be used to train EPA
regional, State and local personnel in noise enforcement.
5-13
-------
REFERENCES
Many of the following documents can be purchased through the U.S.
Government Printing Office (GPO), Washington, D.C., 20402, Phone: 202/
783-3238 or the National Technical Information Service (NTIS), U.S.
Department of Commerce, 425 13th St., N.W., Room 620, Washington, D.C.
20004, Phone: 202/296-4348. A GPO or NTIS document number will be
included with the reference in such cases.
1. Noise Control Act of 1972, Public Law 92-574, 92nd Congress,
H.R. 11021, October 27,1972, 86 Stat. 1234.
2. "Report to the President and Congress on Noise," U.S. Environmental
Protection Agency, Office of Noise Abatement and Control, Washington,
D.C. 20460, EPA Document No. NRC 500.1, December 31, 1971. (GPO Stock
No. 5500-0040) (NTIS No. PB-206-716).
3. "Public Health and Welfare Criteria for Noise," U.S. Environmental
Protection Agency, Office of Noise Abatement and Control, Washington,
D.C. 20460, EPA Document No. 550/9-73-002, July 27, 1973. (GPO Stock
No. 5500-00103) (NTIS No. PB-241 000/AS).
4. "Information on Levels of Environmental Noise Requisite to Protect
Public Health and Welfare With An Adequate Margin of Safety," U.S.
Envrionmental Protection Agency, Office of Noise Abatement and Control,
Washington, D.C. 20460, EPA Document No. 550/9-74-004, March 1974.
(NTIS No. PB-239 429/AS).
5. "EPA Noise Control Program Progress to Date," U.S. Environmental
Protection Agency, Office of Noise Abatement and Control (AW471),
Washington, D.C. 20460, March 1977.
6. "Toward a National Strategy for Noise Control," U.S. Environmental
Protection Agency, Office of Noise Abatement and Control, Washington,
D.G. 20460, April 1977.
7. "Model Community Noise Control Ordinanace," U.S. Environmental
Protection Agency, Public Information Center (PM215), Washington,
D.C. 20460, EPA Document No. 550/9-76-003, September 1975.
8. "Guidelines for Developing a Training Program in Noise Survey
Techniques," U.S. Environmental Protection Agency, Office of Noise
Abatement and Control, Washington, D.C. 20460, EPA Document No.
550/9-75-021, July 1975. (NTIS No. AD-A01 667).
5-14
-------
9. "Chicago Urban Noise Study," BBN Report Nos. 1411, 1412, and 1413,
prepared by Bolt Beranek and Newman Inc., 1970 Ogden Avenue, Downers
Grove IL 60515 for The City of Chicago, Department of Envrionmental
Control, 320 North Clark Street, Chicago IL 60610, November 1970.
10. "State and Municipal Noise Control Activities 1973-1974," U.S.
Environmental Protection Agency, Office of Noise Abatement and
Control, Washington, D.C. 20460, EPA Document No. 550/9-76-006,
January 1976, (NTIS No. PB-251 999).
11. "Noise Source Regulation in State and Local Noise Ordinances," U.S.
Environmental Protection Agency, Office of No'ise Abatement and Control
Washington, D.C. 20460, EPA Document No 550/9-75-020, February 1975.
(NTIS No. PB-245 158/AS).
12. "Handbook for Regional Noise Programs," U.S. Environmental Protection
Agency, Office of Noise Abatement and Control, Washington, D.C. 20460,
EPA Document No. 550/9-74-006, April 1974.
13. "Federal Aviation Administration Advisory Circular No. 150-5050-4
Citizen Participation in Airport Planning," September 26, 1975.
14. "Federal Highway Administration Noise Standards and Procedures,"
Policy and Procedure Memorandum 90-2, February 8, 1973.
15. "Procedures for Abatement of Highway Traffic Noise and Construction
Noise," effective May 14, 1976, Federal Aid Highway Program Manual
of Federal Highway Administration, Volume 7, Chapter 7, Section 3.
16. "Noise Abatement and Control: Departmental Policy, Implementation
Responsibilities and Standards," August 4, 1971, Department of
Housing and Urban Development, Circular 1390.2.
17. "Report on Aircraft-Airport Noise," U.S. Environmental Protection
Agency, Office of Noise Abatement and Control, Washington, D.C.
20460, EPA Document No. Senate 93-8, August 1973, (GPO Stock No.
5270-01936).
18. "Transportation Noise and Its Control," U.S. Department of Transpor-
tation, Washington, D.C. 20590, DOT P5630.1, June 1972. (GPO Stock
No. 5000-0057).
19. "Bureau of Motor Carrier Safety Regulations for Enforcement of Motor
Carrier Noise Emission Standards," Title 19, Code of Federal Regulations,
Chapter II, Part 325.
20. "Federal Railroad Administration Railroad Noise Emission Compliance
Regulations," Title 49, Code of Federal Regulations, Chapter II, Part
210, (Federal Register 42, 42343, August?3, 1977).
21. "Criteria for a Recommended Standard . . . Occupational Exposure to
Noise," U.S. Department of Health, Education, and Welfare, National
Institute for Occupational Safety and Health, Cincinnati, OH 45202,
HSM 73-11001, 1972. (For sale by GPO).
5-15
-------
22. "Industrial Noise Control Manual," U.S. Department of Health,
Education, and Welfare, National Institute for Occupational Safety
and Health, Cincinnati, OH 45202, HEW Publication No. (NIOSH) 75-183,
June 1975. (For sale by GPO).
23. "Compendium of Materials for Noise Control," U.S. Department of
Health, Education, and Welfare, National Institute for Occupational
Safety and Health, Cincinnati, OH 45202, HEW Publication No. (NIOSH)
75-165, June 1975. (GPO Stock No. 1733-00073).
24. "Guidelines on Noise," American Petroleum Institute, Committee on
Medicine and Environmental Health, 1801 K St., N.W., Washington, D.C.
20006, Medical Research Report EA 7301, 1973.
25. Industrial Noise Manual, 3rd edition, American Industrial Hygiene
Association, 66 S. Miller Road, Akron, OH 44313, 1975.
26. Berendt, R.D., Corliss, E.L.R. and Ojalvo, M.S., "Quieting: A
Practical Guide to Noise Control," National Bureau of Standards,
Washington, D.C. 20234, NBS Handbook 119, July 1976. (GPO Stock
No. 003-003-01646-2).
27. Brock, J.T., "Application of B&K Equipment to Acoustic Noise
Measurements," 2nd edition, Bruel & Kjaer Instruments, Inc.,
5111 West 164th St., Cleveland, OH 44142, January 1971.
28. Peterson A.P.G. and Gross, E.E. Jr., "Handbook of Noise Measurement,"
7th edition, Gen Rad, Concord, MA, Form No. 5301-8111-1, 1974.
29. "Noise Control Report," bi-weekly business newsletter published from
the Nation's Capitol. Editor and publisher, Leonard A. Eiserer,
Business Publishers, In., PO Box 1067, Blair Station , Silver Springs,
MD.
30. "Noise Regulation Reporter," private circulation publication, The
Bureau of National Affairs, Inc., 1231 25th St., N.W., Washington,
D.C. 20037.
31. "Noise/News," bi-monthly newsletter of the Institute of Noise Control
Engineering, published by Noise Control Foundation, PO Box 3469,
Arlington Branch, Poughkeepsie, NY 12603.
32. "Sound and Vibration," monthly magazine published by Sound and
Vibration, 27101 E. Oviatt Road, Bay Village, OH 44140.
33. "Noise Control Engineering," bi-monthly journal of the Institute of
Noise Control Engineering, subscription information: Noise Control
Engineering, 9 Saddle Road, Cedar Knolls, NJ 07927.
34. Index to Noise Standards - ASA STDS. Index 1-1976 (national and
international), available from Standards Secretariat, Acoustical
Society of America, 335 E. 45th St., New York, NY 10017.
5-16
-------
Chapter 6
HIGH LEVEL NOISE EXPOSURE AND HEARING CONSERVATION
Noise-induced hearing loss is the most widely recognized and one of
the most significant effects of noise on people. It is now well established
that individuals who are exposed to excessively noisy environments, without
adequate hearing protection measures, will incur permanent and irreversable
loss of hearing due to the noise exposure. However, many people do not
understand the link between noise exposure and hearing loss. Many people
regularly expose themselves to high level noise and needlessly damage
their hearing when the use of protective or preventative measures could
have easily avoided this. This apparent lack of concern on the part of
many people is attributable, to a great extent, to the insidious nature
of noise related hearing loss. The onset of this type of hearing loss is
often very gradual, occurring over a period of years, and frequently not
noticed until the loss of hearing is considerable. Further, the symptoms
of noise induced hearing loss, such as loss of auditory sensitivity and
ringing in the ears, are often deceptive. These symptoms usually subside
after the period of exposure, giving the misleading impression that no
permanent damage has occurred.
This chapter will discuss the hazardous properties of high level
noise; the effects of this noise on the auditory system; and protective
measures which can be utilized to avoid noise-induced hearing loss.
6.1 Hazardous Properties of Noise
From prior research on the auditory effects of noise it is possible
to list those characteristics of noise that contribute most directly
to hearing loss. These characteristics are: overall noise level, frequency
spectrum, exposure duration, and temporal pattern (1). Where possible,
all of these factors should be considered when determining the hazard
posed by a particular noise. Reliance should not be placed on a single
characteristic of the noise. Also, the differences in individual suscep-
tibility must be considered.
6.1.1 Overall Noise Level
Overall A-weighted sound levels of 70 to 80 dB are safe for a large
majority of individuals (2). However, large individual differences in
susceptibility to noise damage exist and even this level may adversely
affect certain persons. It should be recognized that any figure is
essentially a compromise based on assumptions concerning what percent of
the population may realistically be protected, and concerning just what
constitutes a significant hearing loss.
-------
6.1.2 Frequency Spectrum
Research indicates that the ear is most sensitive to frequencies
above 1,000 Hz, and that hearing losses occur more readily at these higher
frequencies. Also, noise containing a large percentage of energy below
4,000 Hz is considered to be more hazardous to hearing than noise containing
most of its' energy above 4,000 Hz (3).
6.1.3 Exposure Duration
Generally, as the length of exposure increases, so does the extent
of the resultant hearing loss. However, this relationship exists only
up to a certian point. Research suggests that occupationally related
permanent hearing loss is most rapid during the first ten to fifteen
years of exposure, but that after this period loss still accures although
the rate of loss is reduced (4).
6.1.4 Temporal Pattern
The relationship between intermittent noise and hearing loss is not
clearly defined. In general, however, intermittent noise has been shown
to be less damaging than continuous noise. For example, four hours of
continuous exposure to 100 dB(A) can be expected to be more hazardous
than an exposure to the same sound energy one hour on and one hour off
over an eight hour day.
6.1.5 Summary
In summary, than, the following general statements can be made
concerning the hazardous properties of noise:
• the louder the noise, the more damaging it will be to
hearing;
• the frequency components of noise between 1,000 and 4,000 Hz
are more damaging than the low frequency components;
• generally, as the length of noise exposure increases, so
does the extent of the resultant hearing loss; and
• continuous noise is generally more damaging than inter-
mittent noise.
6.2 How Noise Damages Hearing
Observations in animals as well as in man show that noise reaching
the inner ear directly affects the hair cells of the hearing organ (organ
of Corti). These hair cells serve an important transducing function in
audition. They convert the.mechanical energy reaching the ear into
neuroelectrical signals, which are carried by the auditory nerve to
the brain. The outer ear, eardrum, and middle ear are almost never damaged
by exposure to intense noise, although in some extreme situations, the
eardrum can be ruptured by very intense impulsive noises. Blasts or
other very loud impulse noises can also damage the organ of Corti by
causing vibrations that simply tear apart some or all of the structure.
6-2
-------
Such injuries are called acoustic trauma. As the intensity of the
noise and time for which the ear is exposed are increased, a greater
proportion of the hair cells and their supporting structures are damaged
or eventually destroyed.
Hearing acuity is generally affected first in the frequency range
from 2,000 to 6,000 Hz with most affected persons showing a loss or "dip"
at 4,000 Hz. If high level exposures are continued, the loss of hearing
will further increase around 4,000 Hz and spread to lower frequencies.
There .is a great deal of individual variation in susceptibility to noise
damage, so there is no single level of noise that separates safe and
unsafe conditions for all ears. Furthermore, neither the subjective
loudness of a noise, nor the extent to which the noise causes discomfort,
annoyance, or interference with human activity, are reliable indicators
of its potential danger to the hearing mechanism (5).
6.2.1 Indications of Noise-Induced Hearing Loss
Two noticeable indications of noise induced damage to the auditory
system are usually evident immediately following exposure to high-level
noise. They are:
1) a loss of auditory sensitivity
2) ringing in the ears (tinnitus).
A loss in auditory sensitivity can be determined by measuring the
change in the absolute hearing threshold level. The absolute hearing
threshold level at which a tone can just be detected. In other words,
it represents the lower limit of our range of audibility. The greater
the hearing threshold level, then, the greater the extent of hearing loss.
An increase in the threshold level that results from noise exposure is
called a noise induced threshold shift. These threshold shifts can be
either temporary or permanent. Temporary threshold shifts decrease over
a period of time until they disappear. Permanent threshold shifts
reflect changes in hearing which do not recover with time. As exposures
are repeated, the ear may become less able to recover from the temporary
threshold shifts and permanent hearing changes are observed.
6.2.2 Determination of a Hearing Handicap
The principal criterion of the extent to which hearing loss is a
handicap is the ability to understand speech in quiet surroundings.
However, much debate exists concerning the implications and significance
of small amounts of hearing loss and most guidelines for the assessment
of the extent of handicap are based only on thresholds for tones in the
region most important for the reception of speech (500, 1000, and 2000 Hz)
The Committee on Hearing of the American Academy of Ophthalmology
(AAOO) has adopted guidelines stating that a handicap exists when the
average hearing threshold level for 500, 1000, and 2000 Hz exceed 25 dB
in the better ear (6). However, research shows that individuals with
hearing losses above 2000 Hz may experience considerable difficulty in
6-3
-------
understanding speech in moderate levels of background noise (7), even
though they don't come close to meeting the AAOO criterion. Hearing
losses above 2000 Hz impair hearing so that it is difficult to
distinguish the sounds of consonants that contain much of the information
required to discriminate speech sounds. Because of this, several states
have now included thresholds for 3000 Hz in the determination of
"significant" hearing loss for their compensation laws.
6.2.3 Presbycusis and Other Factors Affecting Hearing
Presbycusis is the term given to hearing loss specifically ascribed
to the effects of aging. Hearing becomes less sensitive with advancing
age, even in the absence of damaging noise exposure. This effect is most
pronounced at frequencies abouve 3000 Hz (8). At least in Western
cultures, presbycusis appears to be more pronounced in males than in
females, but this may be due to noisy activities that are commonly
engaged in by males.
The probability that a person will develop a hearing impairment
due to noise depends on the pattern of exposure from all noises. It
may be possible to control occupationally related noise exposure, but
the control of nonwork exposures poses a much more difficult problem.
Such nonwork exposures as those experienced in military, recreational,
or other activities have been categorized as "sociocusis" factors (9).
These factors complicate attempts at control of the acoustic environment
and make it very difficult to determine the long term noise dose
(over several years) that must be known in order to establish an accurate
relationship between noise exposure and hearing loss.
6.3 Hearing Conservation Programs
Hearing conservation programs are designed to protect individuals
from the. hazardous effects of noise. Most hearing conservation programs
are based on conditions at the work place, however, it is not unreasonable
to extend these principles and practices to the community where damage
to hearing also occurs.
In all cases, it should be kept in mind that the objective of a hearing
conservation program is to prevent noise induced hearing loss. Simple
compliance with local, State, or Federal rules and regulations generally
will not prevent all noise induced hearing loss in susceptible individuals
because the exposure limits selected for compliance purposes have, by
necessity, been developed with consideration of the economic impact of
control measures. Obviously, the lowest and safest economically feasible
limits are desirable for the well-being of the individual.
An effective program should include three areas of concentration:
Noise assessment, noise reduction, and hearing assessment.
6-4
-------
6.3.1 Assessment of Noise Dose
Noise-hazard areas generally are identified by the time and level
of sound exposures. Measures of time and sound level or "noise dose"
may be measured using a sound level meter and a clock, or they can be
measured directly with dosimeters. The resultant noise doses should
be at least as low as those specified by the OSHA (see Section 6.4), but
should be as low as is feasible for the particular noise exposure location,
6.3.2 Noise Reduction
If the noise assessment indicates that hazardous conditions exist,
several protective steps should be taken immediately. These include:
hearing protection, source modification, and path modification.
Hearing Protection: Primary consideration should be given to
protecting the hearing mechanism. Once a hazard is detected, the
initial steps taken should be aimed at -hearing protections. Source
identification and path identification often require implementation time,
whereas steps to protect hearing can be taken immediately. In some
instances, this can be accomplished by simply breaking up activity periods
or by rotating persons in and out of the hazard area. These procedures
increase the intermittency of the noise and thus decrease the threat of
damage.
Another-means of hearing protection involves the use of personal
protective devices or ear protectors (10). These devices usually take
the form of ear muffs worn over the external ear so as to provide an
acoustical seal against the head, or ear plugs that provide an acoustical
seal at the entrance to the external ear canal. The particular type of
ear protector worn depends on such factors as the individual's ear
anatomy and the environment of the person being protected. It should be
pointed out that the only unequivocal means for evaluating the effective-
ness of personal protectors is to measure the hearing thresholds of the
user periodically.
Source Modification: Attempts at source modification usually begin
with locating the source of the noise. Once located, the source should
be eliminated, modified, or replaced. A detailed examination of
engineering control procedures is beyond the scope of this chapter, but
the interested reader is directed to the many detailed presentations of
this topic (10-13). Suffice it to point out that the use of engineering
control procedures on noisy equipment already in operation may be
difficult and, in many cases, ineffective. Engineering noise control
measures can be used most effectively at the design stage of potentially
noisy equipment. Until recently there has not been a strong demand
by many people for quiet equipment, and available technology has not been
used to full advantage in product design. By all means, the purchase
orders for potentially noisy equipment should have adequate specifications
to provide an incentive for the design of quiet products.
6-5
-------
Path Modification: If it is not possible to obtain enough reduction
of noise level by treatment of the source, the next step is to reduce the
exposure level by modification of the sound vibration path. A number of
steps can be taken to reduce the production and propagation of noise
(10-13). These include the use of:
1) partial and complete barriers placed between the observer
and the source to reduce the level of sound propagated,
2) absorption materials placed on room surfaces and inside
of enclosures to prevent reflection and build-up of noise
levels,
3) xdamping materials placed on vibrating surfaces to reduce
vibration and in turn the level of noise emitted,
4) vibration isolators placed under or around a noise source
to prevent vibration from being transmitted to other
surfaces, such as floors, walls, or enclosure panels,
where additional sound may be generated.
6.3.3 Hearing Assessment
One of the most important phases of the hearing conservation program
involves the measurement of hearing levels of persons exposed to noisy
environments. A program of periodic audiometric evaluations must be
implemented and carried out by a trained technician. Although there are
numerous audiometric tests, most hearing conservation programs rely on a
pure tone absolute threshold test as their principal index of hearing
sensitivity. It the audiogram indicates that losses or changes in hearing
have taken place since the base audiogram was taken, then the person
should be referred for professional evaluation of the change.
6.4 Noise Exposure Limits and OSHA
The development of effective and practical requirements and
procedures for assuring the health and safety of workers who are exposed
to high level noise is very complex. In addition to the very complicated
technical aspects related to the effects of exposure to high level noise,
the procedures for measuring noise dosage, and the procedures for hearing
measurement and impairment assessment, there is also the very important
factor of the economic impact on industry. The Occupational Safety and
Health Administration, OSHA, of the U.S. Department of Labor must face
these difficult problems to meet its responsibility in developing and
enforcing rules and regulations to limit exposures to potentially harmful
noises.
The noise exposure limits set forth by OSHA (14) are designed for
both continuous and impulsive noises. The continuous noise limit is
set at 90 dB measured with an A-frequency weighting for exposures of eight
hours per day, with higher levels being permitted over less time at the
rate of 5 dB for halving of exposure time. For example:
6-6
-------
Level (Lp) Time (T)
90 dB(A) 8 hrs
95 4
100 2
105 1
110 1/2
115 1/4
Exposure to continuous noise levels greater than 115 dB(A) are not
allowed under any circumstances. The limit to impulsive noise exposures
is 140 dB peak sound pressure level.
When daily noise exposure is composed of two or more periods of
exposure at different continuous, steady-state levels, their combined
effect is determined by adding the individuals contributions as follows:
r r r r
_L + 1 + _! + ___ _!!
Tl ' T2• T3 TN
The values C] to C^ indicate the time of exposure to specified levels
of noise, while the corresponding values of T indicate the total time
of exposure permitted at each of these levels. If the sum of the indi-
vidual contributions Cn C0 exceeds 1.9, then the mixed exposures
(1 + ^ + ._.)
'l !2
are considered to exceed the overall limit value. For example, if a man
should be exposed to 90 dB(A) for five hours, 100 dB(A) for one hour, and
75 dB(A) for three hours during an eight hour working day, then the
times of exposure are C, = 5 hr, Cp = 1 hr, C- = 3 hr; and the corresponding
OSHA limits are T, = 8 hr, T~ = 2 hr, and T^ = .infinity." Therefore, the
combined exposure does for this man would be 5/8 + 1/2 + 3/°° ="1.125, which
exceeds the specified limit of 1.0.
The impulsive noise exposure limit of 140 dB peak sound pressure
level of the 1972 OSHA Rules and Regulations (15) does not specify a
limit for the number of impulses that a person can be exposed to in an
eight hour working day, but it can be expected that a limit such as 100
impulses for eight hours may be set in a modification of the OSHA noise
criteria. Perhaps different peak level limits will be specified for a
greater number of impulses, such as 135 dB for 100 to 1000 impulsive
sound exposures; and 130 dB for 1000 to 10,000 impulsive sound exposures;
and 125 dB for more than 10,000 impulsive sound exposures in eight hours.
The noise exposure limits specified by OSHA are not intended to
provide complete protection for all persons. They are set forth as the
most restrictive limits that are deemed feasible with due consideration
given to other factors, such as economic impact. Therefore, wherever
feasible, hearing conservation measures should be initiated at levels
considerably below those specified by OSHA. The ideal action point for
initiating hearing conservation measures would be about 75 dB(A) for
continuous steady-state noise exposures of 8 hours. However, the economic
6-7
-------
impact of limits set at this low sound-pressure level may not be
feasible in many situations. Many activities away from the work place
cause noise exposures greater than 75 dB(A), so something must be done
with the normal life style of this country if exposures are to be changed
radically. Certainly, every effort should be made to institute hearing
conservation measures for extended exposures above 80 dB(A).
Lowering noise exposures has very meaningful benefits other than to
avoid an OSHA citation. Obviously, the most important benefit is that
noise induced hearing loss may be prevented. In addition, the lower levels
will generally afford better working conditions, which should reduce
annoyance and improve communication; thus, safety conditions and the
general well-being of workers should be improved. Economic advantages
of lower noise levels should include increased production and a reduction
in compensation claims (in future years) for noise induced hearing loss.
Also, the OSHA limits for noise exposure may be lowered in t^ie future, so
it is generally more economical to have noise levels as low as is feasible
now rather than attempt control measures twice.
Other widely used noise exposure limits include those developed by the
U.S. Air Force (16), the U.S. Army (17), MESA (18), and the Committee of
Hearing and Bioacoustics of the National Research Council (CHABA) (19).
6.5 Noise Exposure Limits and EPA
The Environmental Protection Agency (EPA) has attempted to identify
the environmental noise levels requisite to protect the hearing of the
general population. EPA has placed an emphasis on the protection of the
hearing of all individuals within an adequate margin of safety as opposed
to the compromise position of OSHA. The data base used to derive safe
levels recommended by EPA consisted of statistical distributions of
hearing levels for populations at various exposure levels. Thie evidence
for noise related PTS was defined as the shift in the statistical distri-
bution of hearing levels for a noise exposed population in comparison to
that of a non-exposed population (20). The interested reader is directed
to Appendix C of reference 20 for a detailed explanation of how these
levels were derived. From these data it was possible to derive the
eight hour exposure level which protects virtually all of the population
from greater than 5 dB PTS. This was found to be 73 dB(A).
In order to apply this eight-hour figure to the environmental
situation, it was necessary to develop several adjustment factors.
Adjustments for intermittency, for twenty-four hour exposures, and for
yearly exposures were developed. EPA defined intermittent noise as noise
which is below 65 dB for about 10% of the time (Lon < 65 dB), with peak
levels of 5 to 13 dB higher than the background (20). In general, environ-
mental noise should be considered intermittent unless shown otherwise (21).
Since intermittent noises are typically less harmful than continuous noises,
a correction factor of +5 dB was derived. Thus, eight-hour exposures to
intermittent noise should not exceed 78 dB.
6-8
-------
The identified level of 73 dB is based on eight hour daily exposures.
Conversion to a twenty-four hour period requires a reduction of this level
by 5 dB. This means that continuous noise of a twenty-four hour duration
must be 5 dB less intense than sounds of only eight-hours duration.
Correction to yearly dose (365 days) requires that the 73 dB
figure be reduced by 1.6 dB. This is because the original statistical
data was based on occupational exposures of only 250 days per year.
Employing the above corrections implies that the average eight-hour
daily dose (based on a yearly average and assuming intermittent noise) .
should be no greater than 73 + 5 - 1.6 = 76.4 dB(A). A similar value for
twenty-four hours would be 71.4 dB(A). EPA suggests that it would be
reasonable to round off the 71.4 dB(A) value to 70 dB(A) to account for
statistical errors and to insure an adequate margin of safety.
As can be seen the EPA levels for all types of exposures are
considerably more stringent than those contained in the OSHA limits.
The EPA recommendations represent a conservative approach directed to
protection of the entire population from hearing loss. The extent to
which such levels would be economically feasible or compatible with the
American life style remains an open question.
6-9
-------
REFERENCES
1. Peterson, A.G. and E.E. Gross, Jr., Handbook of Noise Measurement,
General Radio, Concorde, Mass., Chap. IV, 1974.
2. Ward, W.D., "Effects of Noise on Hearing Thresholds," in W.D. Ward
and J.E. Fricke(Eds.) Noise as a Public Hearing Hazard. American
Speech and Hearing Association Reports, Report 4, 40-48, 1969.
3. Ward, W.D., A. Glorig, and D.L. Sklar, "ITS from Octave-Band Noise-
Applications to Damage Risk Criteria," J. Accoust-Soc. Am.. 31,
522-528, 1959.
4. Glorig, A., Ward, W.D., and Nixon, J., "Damage Risk Criteria on Noise,"
Arch. Oto-Laryngol., 7_4, 413-423, 1961.
5. "Public Health and Welfare Criteria for Noise," U.S. Envrionmental
Protection Agency, EPA Document Number EPA-550/9-73-002, July 1973.
6. Davis, H., "Guide for the Classification and Evaluation of Hearing
Handicap in Relation to the International Audiometric Zero," Trans.
Am. Acad. Ophth. and Otol. 69_, 740-751, 1965.
7. Niemeyer, W. "Speech Discrimination in Noise-Induced Deafness,"
Internat. Audiol. 6^, 42-47, 1967.
8. Gallo, R. and A. Glorig, "Permanent Threshold Shift Changes Produced
by Noise Exposure and Aaing," Amer. Ind. Hyg. Assoc. J., 25.
237-245, 1964.
9. Cohen, A., Anticaglia, J., and Jones, H.H. "Sociocusis-Hearing loss
from Non-Occupational Noise Exposure," Sound and Vibration, 4, 12-23,
1970.
10. "Industrial Noise Manual" American Industrial Hygiene Association,
Southfield, Mich. 1966.
11. Geiger, P.H., Noise Reduction Manual. Engineering Research Institute,
University of Michigan, 1953.
12. Hines, W.A., Noise Control in Industry, Business Applications Limited,
London, 1966.
13. Harris, C.M., (Ed), Handbook of Noise Control, McGraw-Hill, New York
1957.
14. "Occupational Safety and Health Standards" (Williams-Steiger Occupa-
tional Safety and Health Act of 1970), U.S. Department of Labor, Fed.
Reg., 36, 10518 (1971).
15. Occupational Safety and Health Standards, Federal Register, 37, No. 202,
October 18, 1972.
6-10
-------
16. "Hazardous Noise Exposure," Air Force Regulation 160-3, Department
of the Air Force, 1956.
17. MIL - STD - 1474 A (MI), Military Standards, Noise Limits for Army
Material, Department of Defense, Washington, D.C. 20301.
18. Mandatory Health Standards - Underground Coal Mines, Federal Register,
35, 12739, July 7, 1971.
19. Kryter, K.D., W.D. Ward, J.D. Miller, and D.H.Eldredge, "Hazardous
Exposure to Intermittent and Steady State Noise," J. Accoust. Soc.
Am., 39, 451-464, 1966.
20. "Information on Levels of Environmental Noise Requisite to Protect
Public Health and Welfare with an Adequate Margin of Safety," U.S.
Environmental Protection Agency, EPA Document Number EPA 550/9-74-004,
March 1974.
21. "Community Noise," U.S. Environmental Protection Agency, December, 1971
6-11
-------
Chapter 7
EFFECTS OF NOISE ON BEHAVIOR AND WELL-BEING
The most significant effect of noise on humans is permanent noise-
induced hearing loss that may result from high level exposures. However,
the effects of noise on man are not confined to the auditory system.
Noise has been shown to elicit a variety of behavioral and physiological
responses. At the present time, it is not possible to determine the
extent to which these effects represents major threat to human health.
It is very difficult, if not impossible, to separate many of the non- .
auditory effects of noise from the effects of other environmental stresses.
This chapter begins with a discussion of annoyance reactions to
noise. It then discusses noise in relation to our general physical and
mental health and finally considers the effects of noise in several
specific areas, such as task performance, sleep, and speech communication.
7.1 Annoyance and Community Response
Annoyance reactions are perhaps the most widespread response to
noise. Annoyance might best be conceptualized as a psychosocial response
to noise exposure. Noise has often been defined as unwanted sound, and
it is this quality that is most often associated With annoyance. Annoyance
has been studied from two general perspectives: annoyance reactions
of the individual and annoyance reactions of the community.
7.1.1 Individual Reactions
Individual annoyance reactions have ususally been investigated in
the laboratory (1). Many of these studies involve artificial sounds with
well specified properties. This aids the investigator in determining
relationships between the individual's reaction and particular attributes
of the sounds. Participants in these experiments are typically asked
to rate a set of sounds along a certain dimension such as unpleasantness
or to make comparisons between pairs of sounds on the given dimension.
It is generally accepted that annoyance increases with sound level,
and that higher frequency sounds are more annoying. Also, those sounds
that are intermittent ,qr varyinq over time are rated as more annoying than
those that are continuous or invariant. In addition, annoyance appears
to be real ted to the information content of the sound and the extent
to which the sound interferes with some ongoing activity of the individual.
7.1.2 Community Reaction
1 Information concerning community annoyance is usually obtained through
social surveys. Most social survey work has concentrated on population
exposed to either aircraft or surface transportation related noises. In
-------
general, the research appears to suggest that there are a number of
personal, social, and situational factors that appear to intervene
between noise exposure and response. Taking into account the physical
characteristics of the noise, it is possible to predict with some
percision the percentage of individuals in a given community that will
express annoyance with the noise. However, such information will not
result in accurate predictions concerning the response of a given indi-
vidual in that community. Inclusion of certain personal and social
factors, such as those given below, have been shown to improve the
accuracy of these predictors (2).
The following is a representative list of factors which at one
time or another have been found to be related to annoyance. Generally,
individuals are more readily annoyed:
1) when they are indoors as opposed to outdoors,
2) more often at night than during the day,
3) when they live in suburban areas as compared to urban
areas. This, is in part, related to higher background
noise levels in the city,
4) if they perceive the noise level or the source, itself,
to be unnecessary,
5) if they perceive the noise to be a threat to their
personal health and safety,
6) if they perceive the noise to be a threat to their
economic investment (Property value),
7) if they are dissatisfied with other aspects of the
environment,
8) if they feel that the noise is beyond their control,
9) if they feel that they were treated unfairly by the
authorities.
To some extent, the socioeconomic status of the community and its
previous experience with noise are also related to annoyance, but here
the effect is very complicated.
7.1.3 Complaint Activity
Complaint activity in the community is a poor measure of annoyance
level, in that, research has shown that complaints represent only a small
fraction of those annoyed (2% - 20%) (2). Also, people who complain do
do not differ from their neighbors in any significant way, nor are they
particularly sensitive to noise (3). Table 7.1 contains a summary of
day-night noise levels and their respective annoyance and complaint
rates. It is apparent from this Table that any noise level, no matter
how low, will result in some annoyance, but that at any level, complaint
activity underestimates annoyance. Complaint activity should not stand
alone as a measure of annoyance.
7-2
-------
TABLE 7.1
PERCENTAGES OF PERSONS HIGHLY ANNOYED MHO REGISTER COMPLAINTS AS A
FUNCTION OF L.
, Percentage of Percentage
dn Highly Annoyed of Complaints
50 13 Less than 1
55 17 1
60 23 2
65 33 • 5
70 44 10
75 54 15
80 62 Over 20
7-3
-------
7.1.4 Noise Ratings
Considerable interest has been directed at identifying the measure
of noise that best correlates with annoyance. The A-frequency weighting
on sound level meters has been, by far, the most widely used frequency
weighting applied to community noise measurements. Both manual and auto-
matic sampling procedures have been used with the A-frequency weighted
measurement data. This simple A-weighted measure is normally used in such
a way that sound magnitude, frequency distribution, and temporal character-
istics are considered over a period of about 24 hours to describe community
noise exposures. These A-weighted data may be presented as energy
equivalents, Leq, or average A-weighted sound levels that may have adjust-
ments (penalties) for night time. They may also be presented as cumulative
statistical values, L.,, (see Chapter 11).
7.1.5 Implications of Annoyance and Community Response
Annoyance reactions are the most widespread type of reaction to
noise, but these individual annoyance reactions are difficult to predict
on the basis of noise exposure data per se. The addition of personal,
social, and situational information improves the predictive power con-
siderably. But it is generally necessary to go to large numbers of responses
before annoyance levels (community annoyance levels) can be predicted
with reasonable accuracy from noise data alone. Complaint level is almost
always an underestimation of annoyance, in that, only a small proportion
of those annoyed actually complain. It is probably also safe to conclude
that annoyance from noise can never be totally eliminated in any community
setting.
7.2 Physiological Effects of Noise, Stress and Health
The purpose of this section is to present a summarization of current
knowledge on the non-auditory physiological and health effects of noise.
A brief discussion of the general concept of systemic stress is also
presented. The selection of topics for inclusion in this section includes
those topics that appear most relevant and those that have received the
greatest amount of empirical attention.
7.2.1 The N-Response
The N-Response (4,5) is a group of physiological responses to sound.
The response is characterized by:
1) a vasoconstriction of the peripheral blood vessels
accompained by minor changes in blood pressure and
heart rate,
2) slow-deep breathing,
3) changes in electrodermal sensitivity (GSR-galvanic
skin response),
4) a brief change in skeletal muscle tension.
These responses cannot be called fear, startle, or anxiety responses
because some of them are associated with emotion arousing activities
of the autonomic nervous system, while others are associated with emotion
7-4
-------
suppressing activities (4). This pattern of responses begins to appear
with noises below 70 dB, and the pattern appears to show adaptation
in some cases with repeated stimulation (4).
7.2.2 Circulatory System Effects
Laboratory research provides some evidence that noise affects gross
parameters of the circulatory system especially for noises above 100 dB
SPL. Measures'used include blood pressure, pulse rate and heart rate (6).
there is, however, some evidence that working in high noise environments
does result in a greater incidence of circulatory problems than working
in low noise environments (7). But, as is often the case with the field
studies, it is extremely difficult to attribute these effects to noise
per se and not to other stress producing attributes of the work environment.
7.2.3 Pupillary Dilation
There is evidence, mostly from Europe, that noise affects eye pupil
dilation. The magnitude of the effect appears to increase with the in-
tensity of the stimulation, from approximately 70 dB SPL to at least 110
dB SPL (8). The significance of the response is not known at the present
time, but there is an apparent neurological relationship between pupil
dilation and the sense of balance (9).
7.2.4 Startle Effects
Startle is a primitive response that may be evoked by a wide variety
of stimuli. The purpose of the response is to orient the organism to a
potential source of danger. As would be expected, it is particularly
susceptible to loud, unexpected noises. The physiological component of
the response is essentially independent of the stimulus and includes
increased pulse rate, increased blood pressure, and peripheral vaso-
constriction. The behavioral component involves a complex pattern of
body and facial responses as well as muscular flextion. Although the
N-response discussed above and the startle response share certain
similarities, the patterns are different enough that physiologists
consider them to be two different responses (4).
The startle response is normally present at low levels of sound
energy, and does tend to show adaptation as a function of reported
stimulation in many, but not all, individuals (10). There is no evidence
that it produces any lasting harmful effects.
7.2.5 Vestibular Effects
The vestibular organs of the inner ear (sacculus, utricle, and semi-
circular canals) are involved in maintaining body balance and orientation
in space. The fact that organs important for both hearing and balance
exist in such close proximity to each other suggests the possibility of
7-5
-------
an interrelationship between the two senses. Research has shown that
noise can produce dizziness and nystagmus (rapid involuntary side-to-
side eye movements). However, in order to obtain these effects noise
levels exceeding 130 dB SPL are usually required. Somewhat lower levels,
approximately 120 dB SPL, appear to disturb balance, particularly if
the stimulation is unequal at the two ears (11).
At present, there appears to be no evidence that long-term exposure
to noise has any significant effect on the vestibular system (12).
Further research, however, is warranted.
7.2.6 Stress Reactions
Attempts have been made to explain the effects of noise in terms of
physiologic stress theory (13). The theory holds that a large variety
of noxious agents are capable of producing a general stress reaction in
the organism. Stress is largely non-specific in that different stressors
do not each produce a specific set of responses. The organism's response
to a stressor is called the General Adaptation Syndrome (GAS). The
GAS has three stages: the alarm stage, in which the system prepares to
fend off the stressor, the resistance stage, in which the body fights
the stressor, and the exhaustion stage which occurs if the body can no
longer withstand the stressor. If the stressor is severe enough and
present for a prolonged time, the stage of exhaustion is reached and the
end result would be the death of the organism from its inability to defend
itself against the stressor. In less severe instances, the price is paid
in the resistance stage in terms of lowered resistance to infection, and
the development of the so-called diseases of adaptation '- gastro-intestinal
ulcers, elevated blood pressure, arthritis, etc.
It is fairly well established that noise of extremely high level can
act as a stressor, and can, at least for some animals, lead to some of the
reactions associated with the GAS (14). However, the .implications of the
human organism are, at present, very unclear. The theory is logically
compelling, but the vast complexity and generality of theory make the
determination of the effects of a single stressor such as noise a Herculean
task. Consideration must be given to the interaction of various stressors,
individual differences in susceptability to stress, and the apparent
adaptability of the human organism. Large-scale epidemiological and
psychophysiological research is needed.
7.3 General and Mental Health
Health as defined by the United Nations refers not only to the absence
of disease, but to physical, emotional and social well-being (15). Within
the purview of this definition, all of the topics covered in this section
have some direct or indirect relationship to health. Unfortunately, at
the present time, most of these relationships remain undetermined. In fact,
very little can be said about the effects of noise on physical or mental
health. Anecdotal accounts of the pernicious effects of noise abound, but
scientific data is lacking.
7-6
-------
A variety of subjective symptoms such as irritability, anxiety,
nervousness, insomnia, loss of appetite, etc. have been associated with
noise, but the subjective nature of these effects makes their verifica-
tion difficult. Also, field research in noise is often impeded by the
difficulty of separating those effects attributable to noise from the
effects of other stress producing stimuli in the working and living
environment.
The research reviewed in this section suggests that noise does affect
a number of physiological systems of the individual but data are not
available to determine if these effects are of a major consequence to
health.
Noise has been accused of adversely affecting mental health. For
example, recent data suggest a positive relationship between aircraft
noise and mental hospital admissions (16). Unfortunately, the methodolo-
gical criticism of the study was so intense that no valid conclusions
concerning noise and mental health can be derived. There is a serious
and immediate need for well controlled, large scale epidemiological
research in this area.
7.4 Task Performance
Several comprehensive reviews of the effects of noise on task per-
formance have been written ( 4,17,18). There seems to be general agreement
among these reviewers that the research to date has failed to yield a
consistent pattern of effects. Noise has been shown to improve task
performance, to impair task performance, and, in some instances, to have
no apparent effect. Overall, it is probably safe to conclude from these
reviews that the effects of noise on short-term task performance are not
severe in most cases, and that the detection of these decrements requires
detailed performance assessment and the use of noise sensitive tasks.
In a literature review compiled by the EPA, the following conclusions
pertaining to task performance were advanced (9).
• Continuous noise without special meaning does not generally impair
performance unless the sound exposure level exceeds 90 dB(A). Even at
this level the effects are not consistent.
• Intermittent and impulsive noises are more disruptive than steady-state
noises of the same level. Sometimes levels below 90 dB(A) will produce
effects, especially if the bursts come at irregular intervals.
•High-frequency components of noise (above approximately 2000 Hz)
usually produce more interference with performance than low frequency
components of noise.
• Noise usually does not affect the overall rate of work, but may
increase the variability of the work rate.
•Noise is more likely to increase error rates as opposed to rate
of work
7-7
-------
• Complex or demanding tasks are more subject to noise related
impairments than simple tasks.
7.4.1 Characteristics of the Noise. Task, and Individual
The above conclusions suggest that the effects of noise on performance
are related to the nature of the noise, the nature of the task, and the
state of the individual.
Distracting or "attention demanding" noises, such as impulse or
irregular intermittent noises or very intense noises result in greater
task interference.
Most performance decrements have been found on tasks that require
1) continuous performance, 2) prolonged vigilance, or 3) the performance
of two tasks simultaneously. Tasks that require simple, repetitive
operations are unaffected and sometimes enhanced by noise. Obviously,
tasks that require the operator to attend to auditory cues for successful
performance are almost always impaired in the presence of noise.
Noise sensitive tasks, such as those requiring continuous performance
or prolonged vigilance, prevent the individual from pacing their performance
and penalize the individual for momentary lapses of attention. On the
other hand, simultaneous tasks bring about decrements because they over-
load the information processing capacity of the individual. The individual
has a limited capacity information processing system and where noise is
present less spare capacity exists for task information relative to quiet
conditions (19-21). Consequently noise related impairments are often found
in overloading or demending task situations.
The inverted-U theory of arousal has also been used to explain the
variable effects of noise on task performance (22). According to this
theory there exists an optimal level of arousal, below or beyond which
arousal is either sub-optimal or supra-optimal and performance suffers.
In the presence of an arousal increasing stimulus such as noise, performance
on single or boring tasks might be improved because arousal level is in-
creased toward an optimal level. Similarly, the presence of noise during
the completion of a difficult or demanding task might result in a supra-
optimal level of arousal and impaired performance. Tasks of moderate
difficulty would remain unaffected by noise.
There appears to be a great amount of variation in the way in which
different individuals respond to noise, and although this is a common
observation, very little is known about the nature of these differences.
There has, however, been an attempt to apply the inverted-U theory of
arousal to the problem of individual differences (23,24). The basic
supposition of this approach is that individuals differ in their chronic
levels of arousal. If one individual is chronically more aroused than
another, no additional arousal afforded by the presence of nosie would be
more likely to lead to a condition of over-arousal for this individual than
for a less chronically aroused individual. There is evidence linking the
personality dimension of introversion-extroversion to autonomic indices
of arousal and performance. It appears as if introverts are more
7-8
-------
chronically aroused than extroverts. Data is available which suggests
that introverts perform better than extroverts in boring and monotonous
task situations, and that introverts appear to be more adversely affected
by noise than extroverts. These findings must only be considered as ten-
tative, but this does appear to be a promising avenue for future research.
7.4.2. Cumulative and Post Noise Effects
Research has been conducted which indicates that the adverse effects
of noise tend to appear toward the end of task performance sessions (25).
This effect appears to increase in magnitude as time spent in noise increases
(26).
Recent studies have shown that, although noise may not affect per-
formance during the actual exposure, it may produce impairments which
occur after the noise has been terminated (27,28). These adverse
behavioral after-effects have been noticed on tasks involving proof-reading
and frustration tolerance. Apparently noise exposure can cause some
type of residual or depletion effects. Also, more severe after effects
were found with irregular-intermittent and intense (108 dB(A)) noises,
with interim'ttency or unpredictability of the noise being more important
variables than sound level.
These same researchers also found that when subjects were provided
with the means to terminate the noise they were exposed to, the magnitude
of the post-noise effect was reduced even when this control was not
exercised.
7.4.3 Field Studies
Industrial and other work situations do not readily lend themselves
to controlled experimentation. As a consequency, much of the previous
field research has been subject to severe methodological deficiencies (4).
It is usually difficult to separates the effects attributable to noise
from those related to other physical stressors such as heat and air pol-
lution, or to considerations of accident threat and job security. Evalua-
tion of the positive effects of noise reduction efforts are often confounded
by positive morale and motivation changes that also accompany the inter-
vention in the work environment.
More recent work involving a five year study of medical, attendance,
and accident files for 1000 factory workers shows that workers in high
noise settings (>95 dB(A)) had more job related accidents, sickness, and
absenteeism than their counterparts in more quiet settings (<80 dB(A))
(29). These results, too, are subject to criticism because it is quite
possible that high noise levels are found in work situations that differ
in some important respect such as accident hazard from those situations
with lower noise levels.
7-9
-------
7.4.4 Implications of Task Performance Effects
Assessment of the effects of noise on task performance requires
consideration of the particular noise involved, the type of task in
question, and the individuals performing the task. In general, overall
rate of work is not affected, but variability is often increased. De-
manding tasks or tasks that must be performed for relatively long periods
of time are more subject to disruption by noise. Although, in some
situations, performance during noise 'is unaffected, subsequent performance
or behavior sometimes suffers as a result of previous noise exposure.
Most of these conclusions are based on the results of short-term laboratory
research. Valid field research is seriously lacking.
7.5 Sleep Disturbance
There are two aspects to the problem of sleep disturbance: one
concerns actual arousal or waking due to noise, and the other concerns
changes within the sleeping individual who does not awaken with the
noise.
7.5.1 Stages of Sleep
During the course of sleep the individual typically goes through a
progression of different stages of sleep. There are four principle stages,
and these have been differentiated through the examination of brainwave
activity (electroencephologram - EEG). With relaxation the rapid,
irregular waves change to a regular pattern called the alpha rhythm.
Stage 1 follows this period of relaxation, and it is characterized by a
prolonged reduction in wave amplitude and frequency. Later, bursts of
waves (spindle waves) and large slow waves (K-complexes) occur. This is
stage 2. Approximately thirty to forty-five minutes later, bursts of
high amplitude slow waves (Delta waves) commence. This is stage 3.
When Delta waves are present for 50% of the time, the deepest sleep stage,
stage 4, is entered. After approximately sixty to ninety minutes, EEG
activity again resembles that found in stage 1. However, it is accompanied
by rapid eye movement (REM). This is the REM stage, the stage where most
dreaming takes place. It is usually thought that all stages of sleep
are necessary for adequate functioning.
7.5.2 Variables Related to Sleep Disturbance
The major variables that appear related to response to noise during
sleep are age, sex, stage, noise level, rate of noise occurrence, noise
quality, response measures, and presleep activity (30,31).
Age: Middle-aged and older subjects are more affected than children
and young persons at all stages of sleep.
Sex: Women are typically more sensitive to noise during sleep than
men. Middle-aged women are especially sensitive to subsonic jet aircraft
fly overs and simulated sonic booms.
7-10
-------
Stage of Sleep: People tend to be most responsive during sleep
stage 1, next during 2, and then during REM and Delta sleep. Often
times, in the deeper sleep stages noise does not produce behavioral
awakening, but does result in shifts in stage. Usually, the shift is
from a deep to a light sleep. The meaning of the stimulus is also important,
in that, more meaningful stimuli elicit greater response. Delta sleep
appears to be less affected by even meaningful sounds. In general,
behavioral awakening is more likely to occur the longer someone has been
sleeping.
Noise Level: As a general rule, the higher the noise level, the
greater the probability of response, regardless of how the response may
be defined. Research has shown that the probability of being awakened
by 40 dB(A) sound was 5%, increasing to 30% at 70 dB(A). If consideration
is given to changes in EEG, the probability increases to 10% for 40 dB(A)
and 60% for 70 dB(A) (32).
Rate of Noise Occurrence: Research to date has yielded conflicting
findings in this area. For example, low density traffic sounds have
been shown to be more disruptive of sleep than high density sounds, while
on the other hand, jet take-offs were found to be as disruptive at low
rates as at higher rates (33). It is possible that the background noise
levels, the uncertainty and the novelty of the sounds play important
roles in sleep distrubance.
Noise Quality: Meaningful sounds awaken an individual at intensities
lower than those required for meaningless or neutral sounds.
Response Measures: EEG measures are most sensitive to noise stimuli
during sleep. Other autonomic measures such as heart rate and peripheral
vasocontriction are less sensitive than EEG. Measures of respiration
and electrodermal activity are less sensitive still. Motor responses
or simple instrumental responses such as button pressing are least
sensitive.
Presleep Activity: What research there is suggest that pre-sleep
activity such as exercise is not closely related to noise-sensitivity
during sleep. On the other hand, sleep deprivation does seem to increase
the amount of time spent in Delta sleep and REM and consequently should
affect noise sensitivity.
7.5.3 Implications of the Sleep Disturbance Effects
Sleeping in noisy environments appears to produce adverse effects
either in the form of awakening the sleeper, or in the form of shifts in
the stages of sleep. It should be pointed out that the existing data
come almost exclusively from laboratory studies employing relatively few
participants. There does appear to be a relationship between sleep dis-
turbance and annoyance. Community noise surveys have shown sleep distur-
bance to be a major source of annoyance (34).
7-11
-------
Overall, very little is known about the long term effects of sleep
distrurbance. The body needs sleep for normal functioning, and it is
quite possible that sleep disturbance will yield adverse health effects.
This is especially so for these individuals, such as the elderly, that
are most sensitive to noise.
7.6 Speech Interference
Most people have experienced situations in which noise has prevented
them from understanding someone's speech, or where they themselves were
misunderstood. However, little scientific effort was directed to studying
this problem until the advent of the telephone and the development of
mechanized military systems. To date, a considerable amount of laboratory
research has been done, and much is known about how a given speech sound
will be masked by a particular noise (4,35,36). Speech interference is
usually considered as one aspect of the general phenomenon of masking.
Masking refers to the effect one sound has of making another sound more
difficult to hear. One sound may alter the loudness, perceived quality,
or apparent location of another sound.
This specialized laboratory research on masking has had limited
applicability to the problem of ordinary speech. Ordinary speech is a
complicated sequence of sounds with constantly varying level and spectral
distributions. Also, for speech to be intelligible it is not necessary
that all the sounds be heard. Speech is so redundant, and the typical
listener so familiar with the language, that information can be missed
and the speech will still be understood.
7.6.1 Variables Related to Degree of Speech Interference
. There are a number of variables that influence the extent to which
noise will interfere with speech. These are the characteristics of the
speaker and listener, the characteristics of the message, and the
characteristics of the masking noise.
Characteristics of the Speaker and the Listener: Noise will tend to
interfere with speech reception to a greater extent if the speaker has
poor articulation, or if the listener and speaker use different dialects.
Also, lack of extensive knowledge of, and experience with the language will
render communication more difficult in noise, both in terms of their
poor articulation and lower degree of language familiarity, children appear
to suffer more from background noise than do adults with normal hearing
sensitivity. There is tentative evidence that suggest that noise in the
home environment may be related to impaired auditory discrimination and
reading achievement in children (37,38). Decrements in hearing acuity
due to the aging process (presbycusis) also necessitate lower background
noise levels for adequate speech communication (39).
Characteristics of the Message: Research has demonstrated that the
intelligibility of speech in noise is related to the probability of
occurrence of a given sound, word, or phrase (40). In other words,
communications that contain simple and predictable information are less
subject to interference from noise.
7-12
-------
Characteristics of the Noise: As a general rule, the more intense
the noise, the greater will be its interference with speech. The
frequency spectrum of the noise is also very important in that the extent
to which a given noise will interfere with speech depends in part, on the
sound pressure levels of the noise at the speech frequencies.
The effect of intermittent or impulse noise on speech intelligibility
is difficult to assess. The severity of the effect depends on the
frequency and duration of the bursts. As the frequency and duration
increase, the level of speech intelligibility is reduced. Infrequent
bursts of short duration usually do not interfere with speech, in that,
some information can be missed without making the communication unintel-
ligible.
7.6.2 Measures of Speech Interference
Various schemes have been developed to characterize noise in respect
to its speech masking abilities. The two best known are the Articulation
Index (AI) (41) and the Speech Interference Level (SIL) (42). These
measures and their variants allow the user to predict the intelligibility
of speech of a given level in a specific noise. The AI is the more com-
plicated of the two measures because it takes into consideration the fact
that certain frequencies in the noise are more effective in masking the
other frequencies. The SIL provides only a measure of the averaged general
masking capability of the noise with the lowest and highest frequencies
ignored.
•»
The simple A-weighted sound level (dB(A)) is also a useful index
of the masking ability of a noise. The A-weighting process emphasizes
mid-range frequencies, as does the SIL. They differ in that the SIL ignores
the lower frequencies, whereas dB(A) does not. The choice as to which
measure to use depends on the level of accuracy required. The AI is the
most accurate, but it is also the most complicated to use (43). In most
instances, dB(A) or SIL measurements are adequate.
7.6.3 Noise Level, Vocal Effort, and Distance
Attempts have been made to graphically portray the dependence of
intelligibility on distance between speaker and listener with respect
to noise level (44). Figure 7.1 shows the distances over which various
levels. For example, at three feet a "raised" voice can be understood
through a 61 dB(A) noise. By 'understood,1 it is meant that 95% of
the key words in the group of sentences will be comprehended. It should
be pointed out that these figures apply only to outdoor environments.
Predictions for indoor environments would be more complex because
consideration would have to be given to the reverberant qualities of
indoor spaces.
7-13
-------
100
-•J
-Pi
NO VOICE
COMMUNICATION
PARTIAL
COMMUNICATION
EASY
COMMUNICATION
0.5
1 2 34 6 10 15 20
DISTANCE FROM TALKER TO LISTENER IN FEET
35 50 70 100
Figure 7.1 Distance at which ordinary speech can be understood (as a function of A-weighted
sound levels of masking noise in the outdoor environment).
-------
7.6.4 Implications of Speech Interference
Noise does interfere with speech. Research on community noise
indicates that speech interference is a primary source of noise
related annoyance. In certain situations noise may mask signals that, if
not heard, could lead to property damage, personal injury, or even death.
Although people can adapt to even relatively high levels of background
noise, there is evidence that they develop "noncommunicating life styles"
(45), and this is undesirable in terms of the quality of life. There is
also tentative evidence which suggest that noise in the home can adversely
affect the language development of children.
Summary
Permanent noise-induced hearing loss is obviously the best documented
and most signigicant effect of exposure to noise. In addition, however,
noise has been shown to detract in many ways from the quality of life in
our society. It has been demonstrated that, under certain circumstances,
noise can produce annoyance, interfere with speech communication, disturb
sleep, and disrupt task performance. Noise is also capable of eliciting
a variety of physiological responses. At this time, however, there are
conflicting data on the relationships between noise exposure and physical
and mental reactions other than hearing loss. Such effects may exist,
either directly or indirectly, and in view of the lack of significant
health related research it is not wise to draw any conclusions at the
present time.
7-15
-------
REFERENCES
1. Galloway, W.J., Predicting Community Response to Noise from Laboratory
Data, Transportation Noises: A Symposium on Acceptability Data,
Chalupnik, J.D. (Ed), University of Washingtong Press, Seattle, 1970.
2. Tracor, "Community Response to Airport Noise," NASA Report CR-1961,
1971.
3. Alexandre, A., Decision Criteria Based on Spatio-temporal Comparisons
of Surveys on Aircraft Noise, In Proceedings of the International
Congress on Noise as a Public Health Problem, W.D. Ward Ed., pp 619-
626 (U.S. EPA No. 550/9-73-008, 1973.
4. Kryter, K.D., The Effects of Noise on Man, Academic Press, New York,
1970.
5. Davis, R.C., Buchwald, A.M., and Frankman, R.W., Autonomic and
Muscular Responses and Their Relation to Simple Stimuli, Psychological
Monographs, 69, No. 405, 1955.
6. Etholm, B. and Egenberg, K.E., The Influence of Noise on Some
Circulatory Functions, Acta Oto-Laryngol., 58, 208-213, 1966.
7. Jansen, G. Adverse Effects of Noise on Iron and Steel Morkers,
Stahl. Eisen.. 8J_, 217-220, 1961.
8. Jansen, G,, Relation Between Temporary Threshold Shift and Peripheral
Circulatory Effects of Sound, In B.L. Welch and A.S. Welch (Eds.),
. Physiological Effects of Noise, New York: Plenum Press, 1970.
9. "Public Health and Welfare Criteria for Noise," U.S. Environmetnal
Protection Agency, July, 1973. EPA Document Number EPA-550/9-73-002.
10. Landis, C. and Hunt, W.A., The Startle Pattern, New York: Farrar
and Rinehart, Inc., 1968.
11. Nixon, C.W., "Some Effects of Noise on Man," Report No. AMRL-TR-71-53.
U.S. Air Force, Aerospace Medical Research Laboratory, Wright-
Patterson AFB, Ohio, 1971.
12. Dieroff, H.G. and Scholtz, H.J., Zur Frage de Lambedingten
Vestibularissghaden bei begutachteten Larmarbeitern: Z. Largngol.
Rhirol. Otol., 4i6, 746-757", 1967.
13. Selge, H., The Stress of Life, New York: McGraw-Hill Book Company,
1956.
14. Welch, B.L. and Welch, A.S. (Eds.), Physiological Effects of Noise,
New York, Plenum Press, 1970.
15. The First Ten Years of the World Health Organization, Geneva: World
Health Organization, 1958.
7-16
-------
16. Abey-Wickrama, I., Albrook, M.F., Gattoni, F.E.G., and Herridge, C.F.,
Mental-Hospital Admissions and Aircraft Noise, Lancet, 297, 1275-1278,
1968.
17. Broadbent, D.E., Effects of Noise on Behavior, In C.M. Harris (Ed.),
Handbook of Noise Control, New York: McGraw-Hill, 1957.
18. Gulian, E., Psychological Consequences of Exposure to Noise: Facts
and Explanations. In W.D. Ward (Ed.) Proceedings of the International
Congress on Noise as a Public Health Problem, pp. 363-378 (U.S. EPA
No. 550/9-73-008, 1973).
19. Hockey, G.R.J., Effect of Loud Noise on Attentional Selectivity,
Quarterly Journal of Experimental Psychology, 22, 28-36, 1970 a.
20. Hockey, G.R.J., Signal Probability and Spatial Location as Possible
Basis for Increased Selectivity in Noise, Quarterly Journal of
Experimental Psychology. 22^, 37-42, 1970 b.
21. Kahnerman, D., Attention and Effort, Prentice-Hall, Englewood
Cliffs, N.J., 1973.
22. Hebb, D.O., Drives and the C.N.S., Psychological Review 62. 243-254
1956. ~
23. Welford, A.T., Stress and Achievement, Australian Journal of
Psychology. V7_, 1-11, 1965.
24. Welford, A.T., Fundamentals of Skill, Methven, London, 1968.
25. Broadbent, D.E., Decision and Stress, Academic Press, London, 1971.
26. Hartley, L.R., "Effects of Prior Noise or Prior Performance on Serial
Reaction," Journal of Exp. Psych., 101, 255-261, 1973.
27. Glass, D.C. and Singer, J.E., Urban Stress: Experiments on Noise and
Social Stressors, Academic Press, New York, 1972.
28. Wohlwill, J.F., Nasar, J.L., DeJoy, D.M. and Foruzani, H.H., Behavioral
Effects of a Noisy Environment: Task Involvement vs. Passive Exposure,
Journal of Applied Psychology, 61, 67-74, 1976.
29. Cohen. A., Industrial Noise and Medical Absence and Accident Record
Data on Exposed Workers, In W.D. Ward (Ed.), Proceedings of the
International Congress on Noise as a Public Health Problem, pp 441-454,
(U.S. EPA No. 550/9-73-008, 1973).
30. Williams, H.L., Effects of Noise on Sleep: A Review., W.D. Ward (Ed.),
Proceedings of the International Congress on Noise as a Public Health
Problem, pp. 501-511, (U.S. EPA No. 550/9-73-008. 1973)
31. Lukas, J.S., Awakening Effects of Simulated Sonic Booms and Aircraft
Noise on Men and Women, Journal of Sound and Vibration, 20, 457-466,
1972.
7-17
-------
32. Thiessen, G.J., Effects of Noise from Passing Trucks on Sleep,
Report Ql presented at 77th Meeting Acoustical Society of America,
Philadelphia, April, 1969.
33. Schieber, J.P., Etude analytique en laboratoire de I1influence du
bruit sur le sommeil, Centre d/Etuades Bioclimatiques du CNRS,
Strasbourg, France, April, 1968.
34. Lukas, J.S., Measures of Noise Level: Their Relative Accuracy in
Predicting Objective and Subjective Responses to Noise During Sleep,
(U.S. EPA No. 600/1-77-010, 1977).
35. Jeffress, L.A., Masking, In J.V. Tobias (Ed.) Foundations of Modern
Auditory Theory, Vol. 1, Academic Press, New York, 1970
36. Webster, J.C., Effects of Noise on Speech Intelligibility, In W.D.
Ward and J.E. Fricke (Eds.) Noise as a Public Health Hazard, ASHA
Report No. 4, American Speech and Hearing Association, Washington,
D.C., 1969.
37. Cohen, S., Glass, D.C., and Singer, J.E., Apartment Noise, Auditory
Discrimination and Reading Ability in Children, Journal of Experi-
mental Social Psychology/9, 407-409, 1973.
38. Wachs, T.D., Uzgiris, I.C., and Hunt, J. McV., Cognitive Development
in Infants of Different Age Levels and from Different Environmental
Backgrounds: An Explanatory Investigation, Merrill-Palmer Quarterly,
]7_, 283-317, 1971.
39. Palva, A. and Jokinen, K., Presbyacusis: V. Filtered Speech Test,
Acta Oto-Laryngol. 7^, 232-241, 1970.
40. Miller, G.A., Heise, G.A. and Lichten, W., The Intelligibility of
Speech as a Function of the Context of the Test Material, Journal
of Experimental Psychology, 4l_, 329-335, 1951.
41. French, N.R., and Steinberg, J.C., Factors Governing the Intelligibility
of Speech, Journal of the Acoustical Society of America, 19, 90-119,
1947.
42. Beranek, L.L., The Design of Speech Communication Systems, Proceedings
Institute of Radio Engineers, ^, 880-890, 1947.
43. Klumpp, R.G. and Webster, J.C., Physical Measurements of Equally
Speech-Interferring Navy Noises, Journal of the Acoustical Society
of America, 35, 1328-1338, 1963. .
44. Beranek, L.L., Nose Control in Office and Factory Spaces, 15th Annual
Meeting Chem. Eng. Conf. Trans, Bull, 18_, 26-33, 1950.
45. "Effects of Noise on People," U.S. Environmetnal Protection Agency,
December 1971, (NTID 300.7).
7-18
-------
Chapter 8
SOUND PROPAGATION CHARACTERISTICS
Sound propagation over long distances outdoors is affected by
several factors that include:
1) Spherical and cylindrical spreading.
2) Absorption from the earth's surface, from objects in
the propagation path, or from the atmosphere
3) Reflections from objects in the propagation path
4) Transmission loss, or attenuation, from barriers in
the propagation path
5) Weather conditions
a. Humidity gradients
b. Precipitation
c. Temperature gradients
d. Turbulence
e. Wind gradients.
Each of these factors will be reviewed in this chapter.
Sound propagation over short distances is affected by these same
factors; however, the effects of the absorption in the air and the effects
of weather are generally insignificant because there are only slight
changes over the short distances involved. The prediction of sound levels
near to the sound source (near field) is difficult, if not impossible,
in most cases because of complex interactions between factors that include
the sound spectra, the shape and size of the source, the distance from the
source, and other factors. Specifics of short distance propagation will
not be covered here but details can be found in Chapter 2 and in other
reference materials (1,2,3,4,5).
8.1 Spherical and Cylindrical Spreading
The term "long-distance" when applied to sound propagation usually
is intended to mean any distance greater than about 10 times the maximum
dimension of the sound source. However, in community noise work, long
distance generally implies distances greater than a city block.
In most cases sound propagation over long distance also means the
sound source is far enough from the points of measurement so that the
source can be considered to be a point of "point source." Sound will
spread from the point source in a spherical manner and each doubling of
distance from the source will reduce the sound level by about 6dB when
the propagation path is considered as homogeneous.
When the distance from the source to the receiver is small, as might
be the case when measurements are made adjacent to a high traffic density
road where the source consists of many vehicles along the road (the
sound source is more like a line than a point), the sound spreads in a
cylindrical manner. Cylindrical sound spreading usually produces a
sound level drop-off rate approaching 3dB with doubling of distance.
-------
Obviously, there are situations where the sound level drop-off rate will
fall between 3 and 6 dB with doubling of distance, and the drop-off rate
may be even lower than 3 dB with doubling of distance in areas where there
are large reflecting surfaces.
8.2 Absorption Effects from Earth Surfaces and the Atmosphere
It is difficult to discuss the effects of absorption, reflection, or
transmission loss exclusively because of their complex interactions in
practical situations. However, an appreciation of each of these factors
can be developed from practical examples and from some simple theoretical
consideration.
Any material can have an absorption coefficient, a, assigned that
denotes the fraction of sound energy that is absorbed by the material from
an incident sound wave (see Table 8.1). For example, an absorption
coefficient of a = 0.3 would indicate that 30 percent of the incident
energy is absorbed by the material. In terms of decibels (dB) this reduc-
tion in energy would be 10 log ]^_J_ dB = -1.6 dB. Unfortunately, the
treatment of absorption is not this simple because the absorption coef-
ficient of each material depends upon the spectrum of the sound and the
angle of incidence. Thus, the spectrum of the sound must be determined
and high-level frequency bands of interest must be treated separately, or
an approximate absorption coefficient must be determined for an overall
weighted sound level. In addition, absorption coefficients are normally
given for randomly incident sounds and these values may not accurately
describe the coefficients at specific angles of incidence.
For long-distance outdoor sound propagation, where reverberant
spaces are not common, absorption materials may be divided into 2
categories:
1. Poor absorbers and efficient reflectors. Acoustically
hard and smooth surfaces of materials such as brick,
concrete, stone, wood, plaster, water (mud), etc. gen-
erally absorb less than 20 percent of the energy from
incident sound waves (see Table 8.1). Thus, this category
of materials can be considered to be insignificant
absorbers of sound (less than 1 dB).
2. Moderate and frequency selective absorbers. Materials
such as thin panels and porous building materials afford
a significant amount of absorption of sound as shown in
Table 8.1. It should be noted that the absorption coef-
ficients of some of these materials can be changed
considerably by treatment of the surfaces with paint or
glazing.
Absorption or attenuation of sound traveling over the
earth's surface depends upon the structure and the covering
of the ground, and upon the heights of the source and
receiver. Attenuation data have been developed only for
8-2
-------
00
00
Table 8 . 1 Sound Absorption Coefficients of Materials (4) ,
The absorption coefficient (a) of a surface that is exposed to a sound field is the ratio of the sound
energy absorbed by the surface to the sound energy incident upon the surface. For instance, if 55% of the
incident sound energy is absorbed when it strikes the surface of a material, the a of that material would
be 0.55. Since the a of a material varies according to many factors, such as frequency of the noise, den-
sity, type of mounting, surface conditions, etc., be sure to use the a for the exact conditions to be used
and from performance data listings such as shown below. For a more comprehensive list of the absorption
coefficients of acoustical materials, refer to the bulletin published yearly by the Acoustical Materials
Association, 335 East 45th Street, New York, NY 10017.
Materials Frequency (Hz)
Brick — glazed
— unglazed
— unglazed, painted
Carpet — heavy, on concrete
— on 40 oz. hairfelt or foam rubber (carpet has course bad
125
.01
.03
.01
.02
ling) . 08
250
.01
.03
.01
.06
.24
500
.01
.03
.02
.14
.57
1000
.01
.04
.02
.37
.69
2000
.02
.05
.02
.60
.71
4000
.02
.07
.03
.65
.73
—with impermeable latex backing on 40 oz hairfelt or foam
rubber .08 .27 .39 .34 .48 .63
Concrete block—course .36 .27 .39 .34 .48 .63
—painted .10 .05 .06 .07 .09 .08
—poured .01 .01 .02 .02 .02 .03
Fabrics
Light velour—10 oz. per sq yd hung straight, in contact with wall .03 .04 .11 .17 .24 .35
-------
Table 8 . 1 (Continued)
oo
i
Materials
Medium velour — 14 oz. per sq yd draped to half area
Heavy velour — 18 oz. per sq yd draped to half area
Floors
Concrete or terrazzo
Linoleum, asphalt, rubber or cork tile on concrete
Wood
Wood parquet in asphalt on concrete
Glass
Large panes of heavy plate glass
Ordinary window glass
Glass Fiber-mounted with impervious backing — 3 Ib/cu ft, 1" thick
— mounted with impervious backing — 3 Ib/cu ft, 2" thick
— mounted with impervious backing — e Ib/cu ft, 3" thick
Gypsum Board — 1/2" nailed to 2 x 4's, 16" o.c.
Marble
Frequency (Hz)
125
.07
'.14
.01
.02
.15
.04
.18
.35
.14
.39
.43
.29
.01
250
.31
.35
.01
.03-
.11
.04
.06
.25
.55
.78
.91
.10
.01
500
.49
.55
.015
.03
.10
.07
.04
.18
.67
.94
.99
.05
.01
1000
.75
.72
.02
.03
.07
.06
.03
.12
.97
.96
.98
.04
.01
2000
.70
.70
.02
.03
.06
.07
.02
.07
.90
.85
.95
.07
.02
4000
.60
.65
.02
.02
.07
.02
.04
.85
.84
.93
.09
.02
-------
Table 8 . 1 (Continued)
Materials
Frequency (Hz)
125 250 500 1000 2000 4000
oo
i
en
Openings
Stage, depending on furnishings
Deep balcony, upholstered seats
Grills, ventilating
Grills, ventilating to outside
Plaster—gypsum or lime, smooth finish on tile or brick
—gypsum or lime, rough finish on lath
—with smooth finish
Plywood paneling—3/8" thick
Sand
Dry 4" thick
Dry 12" thick
14 Ib water per cu ft, 4" thick
Water
.25-.75
.50-1.00
.15-.50
1.00
.013 .015 .02
.14 .10 .06
.14 .10 .06
.28 .22 .17
.15 .35 .40
.20 .30 .40
.05 .05 .05
.01 .01 .01
.03
.05
.04
.09
.50
.50
.05
.01
.04
.04
.04
.10
.55
.60
.05
.02
.05
.03
.03
.11
.80
.75
.15
.02
-------
general cases, usually with the assumption that the
sound is traveling parallel to the earth's surface,
less than 10 feet above low ground cover (grass or shrubs)
and less than 30 feet above high cover (trees). For these
conditions the approximate attenuation for grass, shrubs
and trees are presented in Figures 8.1 and 8.2 (4).
Details on theoretical calculations and actual measurements
may be found in references 2,4,6,7 and 8-28. A recent
study by Borthwick (29) demonstrates that the attenuation
provided by ground cover should not be considered as
linear, or as being present in units of dB/m. Narrow
belts of trees have been shown to be far more effective
for attenuating sound than wider belts. However, data
are usually presented in this manner for convenience
because of the complex alternatives. In any case, such
attenuation data must be considered as approximate for
general situations.
Absorption of sound by the atmosphere must be described
in terms of the frequency characteristics of the sound,
and the parameters of relative humidity and temperature.
A-weighted sound pressure levels depend mainly upon the
strength of high frequency components; thus, relative
humidity is of primary concern, while temperature changes
contribute only second-order effects (30). Figure 8.3
shows the distances for 3 dB(A) reductions in levels due
to atmospheric absorption as a function of relative
humidity.
8.3 Reflection and Transmission Loss from Barriers
Long distance outdoor sound propagation is affected by surface
reflection and by reflections from, transmission loss through, and dif-
fraction around barriers in the sound propagation path. However, as a
general rule the losses in propagated sound levels are significant only
if either the sound source or the receiver is closer to the barrier than
about 10 times the maximum dimension of the barrier. In an area where
there are strong reflections (a highly reverberant sound field) sound
levels may remain the same or even increase as the distance between the
source and receiver are increased.
Reflections from the earth's surface may also increase the levels of
sound propagation but this effect is generally less than 2 dB over flat
ground surfaces and it is extremely complex to predict over large distances.
Generally, a hard.smooth surface such as concrete, asphalt, or packed dirt
must cover more than half of the distance between the observer and the
sound source for the level to be raised by as much as 2 dB.
The attenuation of sound provided by a barrier depends upon the density
and the physical size of the barrier, and upon the spectrum of the sound
source. The propagation of sound through or around a barrier also depends
upon the acoustical environment on both sides of the barrier. As a
general rule, the transmission loss provided by a barrier will increase
with increasing density of that barrier. However, atmostpheric scattering
8-6
-------
Eicess ottenuotion. dB/30m (100 ft)
DroAOicoOro.
• 1 1
Meisfer
Eynng
•"'
/'
/ /
,'
/
Anolyticol
opproximotion
\ ,
r
^f
//
/
1
63 135 J50 500 1,000 3.OOO 4.000 8.000 16,000
Octave band center frequencies, Hz
Figure 8.1 Attenuation for Sound Propagation Through
Shrubbery and Over Thick Grass, Measured
Data and Analytical Approximation
40
H 3°
E
O
O
fsj
O
—
O
i edge eftects
.
Without edge effects-
Conadion cedar, pine, spruce,
and deciduous forests
31.5 63
Analytical I
~approiimation IOC)"
I
Bore trees
125 250 500 1,000 2,000 4,000 8.00O
Octave bond center frequencies, Hz
Figure 8.2 Attenuation for Sound Propagation in Tree
Zones, Measured Data and Analytical
Approximation for Average U.S.A. Forests.
8-7
-------
1000
CQ
n
I
0)
u
c
n3
4J
W
•rH
Q
100
10
- ft.
-10000-
HlOOO
L-100
"Reddish" Noise
dl ,2
-r?- • f. = const.
"Pink" Noise
dl
df
f = const.
"White" Noise
dl
df
= const.
30 40 50 60 70 80
Relative Humidity (Percent)
90
Figure 8.. 3 Distance for 3dBA Deviation Due to Atmospheric
Absorption vs. Relative Humidity - Temperature •
68°F. Parameter: Spe.ctral Distribution of Intensity
8-8
-------
imposes a practical limit of about 24 dB on the reduction in A-weighted
sound level that can be expected from a barrier. Ground contours and
covers can of course change these limits significantly in some cases.
For additional information use references 13 and 30-33.
8.4 Effects of Heather Conditions on Noise Propagation
The effects of weather conditions on noise propagation are extremely
difficult to predict because of the very large number of different
atmospheric conditions that may have an effect on propagation. When noise
travels over considerable distances through the atmosphere, the sound
pressure level received may vary as much as 25 dB depending upon wind
direction, temperature inversions, precipitation, and other variables.
Also, the sound pressure level will often fluctuate over short periods
of time. Thus, community noise measurements are normally done under calm
and stable weather conditions in order to get the most conservative and
consistent readings.
Wind and temperature gradients may cause "shadow zones" where the
sound is bent upwards, but these effects are very complex and difficult
to predict. On a clear sunny day with winds as low as 10 mph, the
excess attenuation at a given point upwind may be 20 dB higher than for
the same distance downwind.
The presence of fog or precipitation normally reduces the excess
attenuation because wind and temperature gradients tend to be small under
these conditions. Also, there is some Laboratory evidence that fog may
provide increased attenuation above that predicted for molecular
absorption. (34).
Sound traveling through air loses energy from the effects of heat
conduction and radiation, viscosity, diffusion, and from molecular
absorption. In most cases, molecular absorption is the process causing
the major loss of sound energy in noise control problems. In calcula-
tions to determine the amount of sound absorption in air, the frequency
characteristics of the sound, the air temperature, and the humidity are
important factors. For example, for sounds with major frequency components
in the center of the audible band, the excess attenuation due to molecular
absorption will be about 5 dB for distances of about 2000 feet.
It is apparent from this section that sound propagation depends on
the physical characteristics of the sound source, the characteristics of
the medium through which it passes, and the characteristics of objects and
surfaces it encounters along the path from source to receiver. Knowledge
of these principles can aid in controlling the level of sound exposures.
8-9
-------
REFERENCES
1. Morse, P.M. and Bolt, R.H., Sound Waves in Rooms, Rev. Modern
Physics. ]i6, no. 2, 69-150, April, 1944.
2. Delany, M.E. and Bazley, E.N., Acoustic Properties of Fibrous
Absorbent Material, Applied Acoustics, 3_, 10-5116, 1970.
3. Wesler, J.E., "Manual for Highway Noise Prediction," U.S. Depart-
ment of Transportation Report No. DOT-TSC-FHWA-72-1, March, 1972.
4. Winer, F.M. and Keast, D.M., Experimental Study of the Propagation
of Sound Over the Ground, Journal Acoustical Society of America,
31_, pp. 724-733, 1959.
5. Wenzel, A.R., Saturation Effects Associated with Sound Propagation
in a Turbulent Medium, Progress in Astronautics and Aeronautics,
MIT Press, pp. 67-75, 1976.
6. Embelton, T.F.W., Piercy, J.E. and Olson, N., Outdoor Sound Propaga-
tion Over Ground of Finite Impedance, J. Acous. Soc. Am., 59, no. 2,
pp. 267-277, Feb., 1976.
7. Pao, S.P. and Evans, L.B., Sound Attenuation Over Simulated Ground
Cover, J. Acoust. Soc. Am., 49, no. 4, (Part I), pp. 1069-1075,
April, 1971. •
8. Delany, M.E., and Bazley, E.N., A Note on the Effect of Ground
Absorption in the Measurement of Aircraft Noise, JSV, 16, 315-322,
1971.
9. Piercy, J.E., Embleton, T.F.W., and Olson, N., Impedance of Soft
Ground and Its Effect on Practical Measurements, JASA, 54, p. 341(A),
1973.
10. Piercy, J.E., Embelton, T.F.W. and Olson, N., Effect of the Ground
on Near-Horizontal Sound Propagation, Society of Automotive Engineers,
reprint 740211, 1974 SAE Transactions, Sec. 1, vol. 83, 1974.
11. Piercy, J.E., Donate, R.J. and Embleton, T.F.W., Near-Horizontal
Propagation of Sound Over Grassland, JASA, 60, Suppl. 1, 1976,
San Diego, CA.
12. Dickinson, P.O. and Doak, P.E., Measurements of the Normal Acoustic
Impedance of Ground Surfaces, J. Sound Vib., 1_3, no. 3, 309-322, 1970.
13. Jonasson, H.G., Sound Reduction by Barriers on the Ground, J. Sound
Vib, 22^, no. 1, 113-126, May 8, 1972.
14. Lanter, Sean K., A Method for Determining Acoustic Impedance of Ground
Surfaces, Master's Thesis, Department of Mechanical and Industrial
Engineering, University of Utah, June 1977.
8-10
-------
15. Tillotson, J.G., Attenuation of Sound Over Snow-Covered Fields,
J. Acoust. Soc. Am., 39, no. 1, 171-173, January 1966.
16. Nyborg, W.L., Rudnick, I., and Schilling, HiK., Experiments on
Acoustic Absorption in Sand and Soil, J. Acoust, Soc. Am., 22.
no. 4, 422-425, July 1950.
17. Embleton, R.F.W., Thiessen, G.J., and Piercy, J.E., Propagation in
an Inversion and Reflections at the Ground, JASA, 5_9, 278-282, 1976.
18. Scholes, H.E. and Parkin, P.H., The Effect of Small Changes in Source
Height on the Propagation of Sound Over Grassland, J. Sound Vib., 6_,
424-442, 1967.
19. Oncley, P.B., Low Frequency Ground Attenuation in Outdoor Noise
Measurements, J. Acoust. Soc. Am., 31_, 724-733, 1959.
20. McDaniel, O.H. and Reethof, G., The Use of Forests for Noise Control,
Proceedings of the Third Interagency Symposium on University Research
in Transportation Noise. University of Utah, November 12-14, 1975.
21. Leonard, R.E., and Herrington, L.P., "Noise Abatement in a Pine
Plantation," USDA Forest Service Research Note NE-140, 1971.
22. Wenze'l, A.R., Propagation of Waves Along an Impedance Boundary,
J. Acoust. Soc. Am., 55_, 956-963, 1974.
23. Embleton, T.F.W. Piercy, J.E., and Olson, N., Outdoor Sound Propaga-
tion Over Ground of Finite Impedance, J. Acoust. Soc. Am., 59, 267-277,
1976.
24. Pao, S.P. and Evans, L.B., Sound Attenuation Over Simulated Ground
Cover, J. Acoust. Soc. Am., 49, 1069-1075, 1971.
25. Attenborough, K., and Heaps,.N., Sound Attenuation Over Ground Cover,.
The Shock and Vibration Digest 1, 73-83, Oct., 1975.
26. Officer, C.B., Introduction to the Theory of Sound Transmission.
McGraw-Hill, 1958.
27. Zwikker, C. and Kosten, C.W., Sound Absorbing Materials, Elsevier, 1949.
28. Reethof, G., Frank, L.D., and McDaniel, O.H., The Contribution of the
Forest Floor as a Sound Absorbing Element Within a Forest, In press,
to be published as a USDA Forest Service Research Paper.
29. Borthwick, Jesse 0., Attenuation of Highway Noise by Narrow Forest
Belts, M.S., Thesis, Aug., 1977, The Pennsylvania State University.
30. "A Study of the Magnitude of Transportation Noise Generation and
Potential Abatement. Final Report. Vol IV, DOT Report No. OST-ONA-
71-1, November, 1970.
8-11
-------
31. Donate, R.J., Propagation of a Spherical Wave Near a Plane Boundary
with a Complex Impedance, J. Acoust, Soc. Am., 60, no. 1, 34-39,
July, 1976.
32. Donate, R.J., Spherical-Wave Reflection from a Boundary of Reactive
Impedance Using a Modification of Cagniard's Method, J. Acoust. Soc.
Am., 60, no. 5, 999-1002, Nov., 1976.
33. Briquet, M. and Filippi, P., Diffraction of a Spherical Wave by an
Absorbing Plane, J. Acoust. Soc. Am., 6J_, no. 3, 640-646, March, 1977,
34. Paul, D.I., Wave Propagation in Acoustics Using the Saddle Point
Method, J. Math. Phys., 38, 1-15, 1959.
8-12
-------
Chapter 9
LAND USE PLANNING AND NOISE CONTROL TECHNIQUES
The achievement of acceptable noise levels in the community requires
that the community include noise as an element in its planning effort.
Care should be taken to assess the noise impact of new developments, high-
ways, and airports before they are built. It is much easier to control
noise in this manner. There are, however, some techniques that can be used
to ameliorate existing noise problems. The present chapter will discuss
both the prevention of noise problems through intelligent planning and
the reduction ofnoise through physical control measures.
9.1 Land Use Planning
The demands of expanding urbanization coupled with the diverse interest,
to be accommodated in the typical community necessitate that communities
take positive steps to plan their futures. As part of this effort, consid-
eration should be given to the noise environment of the community. Several
extensive discussions of planning and noise control have been published
(1-4), and from these reviews four major planning or planning-related
techniques applicable to the problem of nosie control can be identified.
These include: comprehensive planning, zoning, site planning, and building
design. It should be pointed out that planning related solutions are future
oriented -- they seldom provide immediate answers.
9.1.1 Comprehensive Planning
Most communities spend considerable time and money developing a
comprehensive plan. This usually takes the form of a public document
that contains policy guidelines for the community's future physical
development. The typical comprehensive plan contains statements pertain-
ing to the private uses of land, community facilities, and transportation
(5). Almost without exception, a major aspect of these plans is land use
compatibility. The problem is to provide areas compatible for different
land uses such as industry, commerce, recreation, and residential living,
and to interconnect these areas with a transportation network (4).
Land use policies should not be set without serious, consideration of
the noise environment. But only recently have attempts been made to give
such consideration. The impetus for this has come from several directions.
First, there is an increasing awareness of and concern for environmental
quality among the general public. Second, the National Environmental
Policy Act (6) passed in 1969 requires the preparation of environmental
impact statements for all federal government related projects affecting
the quality of the human environment. And third, various Federal agencies
-------
such as the U.S. Department of Housing and Urban Development (HUD) and
the Federal Highway Administration have issued noise standards which
must be fulfilled before funds can be obtained (7,8). In addition, other
environmental and health and safety legislation passed in the previous
10 years has had, at least, an indirect influence on concern with noise
pollution. Given these circumstances, planning without respect to noise
can prove costly to the community both in terms of time and money.
In the development of the comprehensive plan, primary attention should
be given to airports and surface transportation systems as these are the
most pervasive noise sources in the typical community. Care should be
taken to insure that development in the immediate environs of these sources
is either discouraged or closely scrutinized in terms of its compatibility
with the existing environment. Compatible uses for lands surrounding air-
ports and other high noise areas might include (3):
1) Land uses involving few people, such as warehouses,
sewage treatment plants, reserviors, etc.
2) Uses which are inherently noisy, such as truck terminals,
printing plants, etc.
3) Indoor uses -- where sound insulation would protect
those indo9rs.
Industrial and recreation areas provide other major sources of noise
in the community. Very often the development of industrial parks serves
to separate industrial areas from residentail areas. In the planning of
recreation areas care should be taken to separate these facilities from
noise sensitive areas such as hospitals and schools. Sometimes the
inclusion of recreation areas in large sections of open space allows the
noise emanating from such a facility to dissipate before it intrudes into
a more sensitive area. For the most part it is desirable to separate
certain types of recreation areas from high noise areas as well.
At this time, it is not possible.to enumerate a list of do's and
don'ts for controlling noise through' comprehensive planning. The
important point is that each community should consider noise as an element
in their planning strategy. In.any event, a noise map of the community should
be developed. This map snould identify areas of hign noise as well as noise
sensitive areas. Such a map could serve as a guide to future development,
and insure that noise impact is a consideration in land use decisions
affecting the future of the community.
9.1.2 Zoning
Zoning is probably the most popular means of implementing the com-
prehensive plan. Zoning is a legal technique which classifies an area
into districts, and specifies permitted land uses for each district. These
ordinances often contain building height, size, and setback limitations
as well as open space and population density regulations. Traditionally,
zoning ordinances have specified the type of land use permitted in an
area, but more recently many zoning efforts have become performance
based. That is, an area might be zoned as light industrial by a set of
performance standards such as maximum allowable noise levels. The
ordinances in effect today show wide variation in the noise levels
9-2
-------
permitted (9,10). Figures 1, 2, and 3 summarize graphically the noise
levels set by some current municipal noise ordinances for residential,
business/commercial, and manufacturing/industrial land use districts
respectively.
The EPA model community noise ordinance (see Chapter 5) contains a
section on land use provisions. These provisions are designed either to
be included as part of the noise ordinance itself, or as amendments to
existing land use or zoning laws. Since, in terms of its noise problems,
each community is somewhat unique, the drafters of the model ordinance
made no attempt to set specific limitations for particular zones or
land uses. The determination of performance standard noise levels and
hours of curfew are left up to the discretion of the community. However,
guidelines concerning safe levels of environmental noise have been
compiled by the EPA (11). Table 9.1 contains a brief summary of those
noise levels that have been deemed by the EPA as being adequate to protect
the individual from hearing loss and from disruption of indoor or outdoor
activities.
Zoning is not without its problems. One major problem centers on the
issue of jurisdiction. For example, regional airports are often located
in more than one political unit, and thus adequate zoning requires the
enactment of laws from more than one unit. Solution to this type of
problem requires some form o'f cooperate activity among the units involved,
or the establishment of a single metropolitan agency empowered to zone
the total area.
In order for zoning approaches to noise control to be successful,
there must be a serious committment to noise control in the community.
In many communities variances are routinely granted, and this counteracts
the best designed zoning attempt.
9.1.3 Site Planning
Good site planning can aid in the attenuation of noise from exterior
sources as well as the restriction of noise to surrounding property line
boundaries. The achievement of noise reduction through site planning
requires a thorough knowledge and understanding of the characteristics of
sound propagation (see Chapter 8). Developers should be required to
present noise contours for proposed development sites, and these should
be reviewed by some appropriate agency or authority to insure that noise
levels do not exceed prescribed limits. Building heights, densities, and
configurations all influence noise levels. An extreme example of this is
the placement of tall skyscrapers close together virtually at the curbs
of busy streets. Such an arrangement creates a pattern of reflections and
reverberations called a "noise corridor" (4). Consideration should be
given to the elevation and topography of the proposed site as they can
influence the nosie characteristics, of the site. For example, the con-
struction of an apartment building on the crest of a hill may subject
residents to considerable noise from the traffic arteries below (12).
At the same time, the physical characteristics of the land surrounding the
site, such as forests, hills, bodies of water, etc. also contribute to
the total noise environment and thus should not escape scrutiny.
9-3
-------
35
DAYTIME LEVELS £
NIGHTTIME LEVELS Qj
AVERAGE DAY 56.75
AVERAGE NIGHT - 51.76
117 CITIES - DAYTIME LIMITS
: is CITIES • NIGHTTIME LIMITS
•
®
FIGURE 1
FIXED SOURCE NOISE LEVELS ALLOWABLE AT
4
RESIDENTIAL DISTRICT BOUNDARIES
<
r
>
J, »
ii £ a o
an
t
I
»
c
: g.
D
CD*
[
]
<
D [!]•
.•• n
•
]
r
•
Q
:
i
i
D 8 o ^
• «Tnn «
85
30
70 65 60
A-WEIGHTEO SOUND LEVEL IN dSA
55
50
45
Fig 9.1 Fixed Source Noise Levels Allowable at Residential District Boundaries
-------
40
VD
cn
90
DAYTIME LEVELS
NIGHTTIME LEVELS
AVERAGE DAY . 63.32
AVERAGE NIGHT - 59.21
104 CITIES- DAYTIME LIMITS
104 CITIES NIGHTTIME LIMITS
I I FIGURE II I I
FIXED SOURCE NOISE LEVELS ALLOWABLE AT
BUSINESS/COMMERCIAL DISTRICT BOUNDARIES
..
-D
D
n
y
85
80
-D
•Ms 4
75 70 65 60 55
A WEIGHTED SOUND LEVEL IN dBA
•£
Fig 9.2 Fixed Source Noise Levels Allowable at Business/Commercial District Boundaries
-------
vo
en
ul 'III
20
15
10
i
DAYTIME LEVELS A
NIGHTTIME LEVELS [_]
AVERAGE DAY -67.54
AVERAGE NIGHT - 64.24
112 CITIES -DAYTIME LIMITS
113 CITIES -NIGHTTIME LIMITS
5
FIGURE III
FIXED SOURCE NOISE LEVELS >
MAN
t
-,.
J
«
1
.
d
b
.
e
Al
UFACTURING/I
NDUSTRIALDIS
1
t:
•'•
• D
a
D
«•*
p .
1
^LLOWABLE AT
TRICT BOUNDA
LJ
Dr-D
RIES
rn
0.
•D D
0 .C
90
75
70 65 60
A WEIGHTED SOUND LEVEL IN aBA
50
Fig. 9.3 Fixed Source Noise Levels Allowable at Manufacturing/Industrial District Boundaries
-------
Table 9 .1
SUMMARY OF NOISE LEVELS IDENTIFIED AS REQUISITE
TO PROTECT PUBLIC HEALTH AND WELFARE
WITH AN ADEQUATE MARGIN OF SAFETY
EFFECT
LEVEL
AREA
Hearing Loss
All areas
Outdoor activity
interference and
annoyance
Ldn><55dB
Outdoors in residen-
tial areas,and farms
and other outdoor
areas where people
spend widely varying
amounts of time and
other places in which
quiet is a basis for
use.
Leq(24)«55dB
Outdoor areas where
people spend limited
amounts of time, such
as school yards, play-
grounds, etc.
Indoor activity
interference and
annoyance
dB
Indoor residential
areas
Other indoor areas
with human activities
such as schools, etc.
1. Detailed discussions of the terms L and L appear in
Chapter 11. Briefly,
represents the sound energy
averaged over a 24-hour period while L, represents the
L with a lOdB nighttime weighting.
9-7
-------
In large scale developments the buildings comprising the development
can be oriented in various ways to form optimum acoustical shielding. The
orientation of a U-shaped building so that its open side directly faces
the roadway creates a highly reverberant and-thus undesirable location.
Simply turning the buidling around and orienting it away from the street
reduces this problem, while at the same time providing a protected
outdoor courtyard (12). Separation of play fields from classrooms in a
school site, or the location of an apartment complex swimming pool away
from an apartment courtyard can also contribute to noise level reduction.
Noise factors should be a central aspect of a good site plan.
Highways that must go through residential areas should be designed
with as few intersections as possible. Sharp grades requiring hard
acceleration or deceleration should also be avoided. One way to reduce
highway noise is to build a "depressed" highway which is built below
the general elevation of the landscape. Changes such as these often
accompany development. Such secondary impacts as poorly designed traffic
patterns or poorly synchronized traffic lights should be anticipated in
any development.
9.1.4 Building Design
It should be pointed out that noise reduction achieved through good
building design protects the individual only while he or she is inside
the structure. Although to some extent, the use of sound absorbing
materials on the exteriors of buildings can result in lower outdoor noise
levels. The shape of the building itself can also affect the outside
noise level. Interior design considerations such as location and
arrangement of sleeping and living quarters in homes or classrooms
and cafeteria in schools can contribute to the reduction of interference
from noise and provide acoustic privacy. The use of sound absorbing
materials and furnishings also aid in interior noise reduction.
At the heart of the building design aspect of noise control is the
issue of building codes. There are two general types of building codes
-- performance codes and material codes. Performance codes specify a
certain performance level in noise reduction for the particular structure,
component, or machine in question. Material codes specify in detail the
particular material to be used in a particular type of construction.
Overall, performance codes are more effective if properly enforced, while
material codes take the burden off enforcement requirements. On the
other hand, material codes have been accused of discouraging innovation
in building materials (2).
Largely as a matter of necessity, many European countries have
developed building codes that are more advanced than those in the U.S.
However, the pressures of urbanization, population growth, and energy
conservation should contribute to the improvement of building codes in
the U.S.
9-8
-------
9.1.5 Other Planning Related Techniques
In addition to the techniques and actions discussed above, there are
other actions that a community can take to control noise. Most of these
techniques have been employed in the past to curb airport noise.
The community can pass restrictions that although not eliminating the
source, will reduce its disruption of human activity. Communities can
ban aircraft landings at certain times of the day or night. Within safety
limits, airports can alter runway usage to reduce noise. Steps can be
taken to closely monitor noise levels under flight paths and thus insure
the enforcement of FAA promulgated flight procedures. Truck noise can
be reduced through the establishment of truck routes or through the banning of
truck traffic in selected areas at certain times of the day or night.
The use of financial incentives also may be an effective means of
controlling noise. Landing fees at airports can be manipulated to encourage
landings at ceratin times and to discourage landings at other times. Pre-
ferential tax treatment can be used to discourage development in high
noise areas, or to encourage the use of sound proofing. A limitation in
extension of utilities such as electricity, gas, etc. might also be used
to discourage development in certain areas.
Communities can defend themselves from a noise source by the direct
purchase of land surrounding the source. This action provides a noise
"buffer zone" that discourages both development near the source and the
further encroachment by the source into the community. Direct payments
of money to compensate those whose property use is interfered with by
noise (avigation easements) is another possible action. Obviously, this
approach does nothing to improve environmental quality.
Community noise ordinances often help in noise reduction. Most
ordinances have traditionally fallen under the category of nuisance-
type laws, which prohibit noises that are deemed "excessive and unnecessary".
Nuisance ordinances are by definition subjective, and have in practice
proven difficult to enforce. Recently attempts have been made to write
more objective laws. These objective ordinances attempt to define unlawful
noise in measureable terms (dB), and to use technical measurements in
enforcement. These laws typically provide disturbance provisions as well
as performance standards for motor vehicles and other sources of community
noise (see Chapter 5).
9.1.6 Summary
The purpose of this section has been to discuss some of the planning
and planning-related techniques for noise control. The major point of '
this section is that active consideration to noise should be given in the
planning efforts of every community. The approach to noise control taken
by a particular community depends on the nature of the noise sources and
their impact, and on the envrionmental and economic circumstances of the
community to select those tools and actions that are most appropriate for
its particular noise problems.
9-9
-------
9.2 Physical Noise Control Procedures
If a noise problem exists after a significant effort has been made
to eliminate the problem by comprehensive planning, zoning, site planning,
or building design, then physical means of noise control must be used.
This section will describe some ways to control sound propagation by
physical procedures.
9.2.1 Barriers
A barrier is a partition that is placed between the source of sound
and the listener. It can be either a full enclosure or simply a single
wall. To block the passage of sound the barrier must be rigid and massive
within practical limits.
A barrier can be used effectively to impede that transmission of
sound from the source to the receiver. Barriers can be effective in "small
scale" sound control problems as well as in "large scale" sound control
situations, although the physical dimensions of the barriers used in
each of these situations will be considerably different.
Complete Enclosures: Small scale sound control refers to situations
where either the sound source or the receiver can be completely enclosed
by the barrier. Such situations are found in homes and offices where
noisy machines can be installed in a separate room that will contain the
noise. In homes, the heating plant and laundry equipment are often in-
stalled in a separate room that can be closed off from the living spaces.
Noisy machines in work places can often be completely enclosed to reduce
emitted noise levels. When an enclosure is used to reduce the sound
radiated by a machine, it is often necessary to mount the machine on
vibration isolators before installing the enclosure. This reduces the
direct transmission of vibration through the floor or other mounting
surface where it could be radiated again as sound energy, thus by-passing
the enclosure (13,14,15). For larger, more complex noise sources, the
machine operator can be enclosed in a sound isolating room where the machine's
controls can be located. For example, the operator of a tractor, crane,
or even a room full of machines may be completely enclosed by the body
of the cab or operations room. The amount of sound reaching the operator's
ears is then dependent on the ability of the cab or operations room to
shut out noise. Complete enclosures of practical designs generally will
provide a noise reduction in excess of 10 dB in the low frequencies and
in excess of 30 dB in the high frequencies. Caution must be taken to
ensure that there are no unnecessary openings in any barrier or
enclosure. Figure 9.4 shows the average transmission loss of a single
barrier as a function of barrier mass and percentage of open area. A
table of sound transmission loss of general building materials and
structures is included for general reference in appendix A to this chapter.
9-10
-------
GO
30
25
20
55 15
<
cc
D
O
10
1 I T
SEALED
0.3% OPEN'
I % OP EN
3% OPEN
T T
I I I
I
I I
1.0 1.25 1.5 1.75 2 2.5 3
BARRIER WEIGHT (Ib/sqft)
3.5 4
Figure 9.4.
Average transmission loss of a single
Barrier as a Function of Barrier Mass
and Percentage of Open Area.
9-11
-------
Partial Enclosures: In dealing with large scale noise problems which
are frequently encountered in communities, it may not be possible to employ
complete enclosures; however, partial enclosures can be effectively employed
in many situations. One of the most common uses of partial barriers is
to reduce the noise radiated from busy highways. These partial barriers
can be either natural structures, such as earth berms or ridges due to
natural land contours, or man-made structures in the form of walls erected
between the highway and the sensitive areas. The design principles are
the same for either type of barrier and will be summarized below.
The geometry of a simple barrier is shown in Figure 9.5. Traffic
noise is transmitted directly to observers who may be along the line-of-
sight with the source of sound. Normally, sound traveling along this path
will be attenuated only by spherical propagation, i.e., 6 dB per doubling
of distance. Sound diffracted into the shadow zone will be subjected to
additional attenuation due to the bending of sound around the edge of the
barriers. The amount of attenuation is proportional to the amount of
bending. Although a certain amount of sound may be transmitted directly
through the barriers, the contribution of the transmitted sound to the
total sound level in the shadow zone is usually negligible for most
practical barrier designs. Of course, an observer on the side of the
roadway opposite from the barrier will receive not only the direct sound
Propagated in that direction, but will also receive sound reflected from
the barrier. This reflected sound must be taken- into account when con-
sidering the impact of the barrier on the surrounding community. The
length of the barrier along the roadway must also be considered when
estimating the sound attenuation as illustrated in Figure 9.6. Sound from
the roadway can also reach the observer (receiver) by a direct path past
the end of the barrier.
The noise reduction achieved through various configurations of
specific barriers or enclosure materials may vary significantly. Generally,
a single-wall barrier with no openings between the source and the person
exposed might result in a 2 to 5 dB reduction in the low frequencies and
a 10 to 15 dB reduction in the high frequencies. If the noise source and
the observer are close to the barrier, higher reduction values are possible.
The effects of two- or three-sided barriers are difficult to predict on
a general basis; however, well-designed partial enclosures may provide a
noise reduction of about 5 to 10 dB in the high frequencies.
Complete information on the design of barriers for reducing highway
nosie in residential areas may be found in references 16 through 18.
Anecdotal accounts of community experiences with barriers and their reac-
tion to them found in reference 19 . Table 9.2 is a practical guide to
the amount of attenuation that can be attained by the use of single-wall
barriers.
9.2.2 Landscaping
Careful planning of land contours and suitable planting of trees and
shrubs along the edge of highways can also be used as barriers for sound
reduction. "Natural" barriers of this, type are generally more pleasing
to the eye and consequently are more readily accepted by residents in
9-12
-------
FIGURE 9.5 NOISE PATHS FROM ROADWAY TO RECEIVER
PLAN
ROAD WAY
FIGURE 9.6 SHORT-CIRCUIT OF BARRIER AROUND ENDS
9-13
-------
Table 9.2
Barrier Attenuation
Transmission Loss* Attainability
5 dB(A) Simple
10 dB(A) Attainable
15 dB(A) Difficult
20 dB(A) Attainable only by careful design
24 dB(A) Maximum attainable under ideal
conditions
*Note: A barrier modifies the sound spectrum in that it
attenuates high frequencies more than low frequencies. For
this reason, the difference between sound levels measured
before and after installation of the barrier will depend
on the sound level meter weighting used. That is, the
attenuation measured with A-weighting may be different
from attenuation measured with C- or Plat-weighting. In
most cases the A-weighting network will be used for noise
measurements, but octave- or third octave-band levels may
be required to provide additional information on the attenua-
tion characteristics of barriers.
9-14
-------
the area; however, the amount of sound reduction that can be attained
with these barriers is limited.
A dense planting of trees that have abundant foliage used with dense
underbrush or ground cover should afford about 5 dB(A) reduction in noise
level. Additional plantings may provide an additional 5 dB(A) reduction
in noise but this is the maximum that can be expected from this type of
acoustic barrier. The attenuation of this "natural" barrier is usually
much less when the vegetation is first planted and increases to this
maximum limit as the foliage develops over a period of years. Additional
information on the effectiveness and design of "natural" forest-type
sound barriers may be found in Chapter 8 references (20,21,28, and 29).
9.2.3 Combinations of Noise Control Procedures
A single noise-control procedure may be ineffective by itself but,
when coupled with one or more other procedures, may produce significant
results. As an example, a typical indoor noise source with a frequency
spectrum in which all octave-band pressure levels are essentially the
same may have the following noise-reduction values for the seven noise-
control procedures shown in Table 9.3.
9-15
-------
Table 9 . 3
Effectiveness of Noise Control Procedures
Noise-Reduction Noise Reduction Octave Band Frequency (Hz)
Procedure 31.5 63 125 250 500 1000 2000 4000 8000
1.
2.
3.
4.
5-
6.
7.
Mounted on
Vibration
Isolators 11 73---
Single-Wall
Barrier - -3'566 6 6
Complete En-
closure of
Absorbing
Material - ---455 6 7
Complete En-
closure of
Solid Mater-
ial with No
Absorption
Inside - 2 5 14 18 26 26 27
Complete En-
closure of
Solid Mater-
ial with No
Absorption
Inside Mounted
on Vibration
Isolators 11 8 7 16 21 29 34 35
Complete En-
closure of
Solid Mater-
ial with Ab-
sorption In-
side Mounted
on Vibration
Isolators 11 11 13 25 32 38 40 42
Complete No. 6
Procedure
Mounted on Vi-
bration Iso-
lators and
Enclosed in
Solid Mater-
ial with Ab-
sorption
Inside 20 17 22 44 50 57 57 59
-
7
7
29
40
45
64
9-16
-------
APPENDIX A TO CHAPTER 9
9-17
-------
Sound transmission loss (in dB) of general building materials and structures (l5)
The sound attenuation provided by a barrier to airborne diffuse sound energy may be described in terms of
its sound transmission loss (TL)i TL is defined (in dB) as ten times the logarithm to the base 10 of the
ratio of the acoustic energy transmitted through a barrier to the acoustic energy incident upon its oppo-
site side. It is a physical property of the barrier material and not of the construction techniques used.
Material or Structure Frequency (Hz)
125 175 250 350 500 700 1000 2000 4000
Doors
Heavy wooden door—special hardware; rubber
gasket at top, sides and bottom; 2.5" thick;
UD
oo 12.5 Ib/sq ft 30 30 30 29 24 25 26 37 36
Steel clad door—well-sealed at door casing
and threshold 42 47 51 48 48 45 46 48 45
Flush—hollow core; well-sealed at door cas-
ing and threshold 14 21 27 24 25 25 26 29 31
Solid oak—with cracks as ordinarily hung;
1.75" thick 12 15 20 22 16
Wooden door (30" x 84"), special soundproof
construction—well-sealed at door casing and
threshold; 3" thick; 7 Ib/sq ft 31 27 32 30 33 31 29 37 41
-------
(Continued)
I
—I
'-£>
Material or Structure
125
175
Frequency
250 350 500
(Hz)
700
1000 2000
4000
Glass
0.125" thick; 1.5 Ib/sq ft 27
0.25" thick; 3 Ib/sq ft 27
0.5" thick; 6 Ib/sq ft 17
1" thick; 12 Ib/sq ft 27
Walls — Homogeneous
Steel sheet — fluted; 18 gage stiffened at edges
by 2 x 4 wood strips; joints sealed; 4.4 Ib/sq ft 30
Asbestos board — corrugated, stiffened hori-
zontally by 2 x 8 in. wood beam; joints sealed;
7.0 Ib/sq ft 33
Sheet steel— 30 gage; 0.012" thick; 0.5 Ib/sq ft 3
—16 gage; 0.598" thick; 2.5 Ib/sq ft 13
. —10 gage; 0.1345" thick; 5.625 Ib/sq
ft 18
—0.25" thick; 10 Ib/sq ft 23
29
29
20
31
20
29
6
18
23
28
30 31 33
31 32 33
22 23 24
32 33 35
20 21 22
31 34 33
11
23
28
38 33 41
34
34
27
36
17
33
16
28
33
38
34 34
34 34
29 34
32 37
30 29
33 42
21
33
38
46 43
42
42
24
44
31
39
26
38
43
48
-------
(Continued)
Material or Structure Frequency (Hz)
125 175 250 350 500 700 1000 2000 4000
Sheet steel—0.375" thick; 15 Ib/sq ft 26 31 39 36 42 41 47 41 51
—0.5" thick; 20 Ib/sq ft '28 33 38 43 48 53
Sheet aluminum—16 gage; 0.051" thick;
0.734 Ib/sq ft 58 13 18 23 28
—10 gage; 0.102" thick;
1.47 Ib/sq ft 8 14 19 24 29 34
f Plywood—0.25" thick; 0.73 Ib/sq ft 20 19 24 27 22
i\>
—0.5" thick; 1.5 Ib/sq ft 8 14 19 24 29 34
—0.75" thick; 2.25 Ib/sq ft 12 17 22 27 32 37
Sheet lead—0.0625" thick; 3.9 Ib/sq ft 32 33 32 32 32
—0.125" thick; 8.2 Ib/sq ft 31 27 37 44 33
Glass fiber board—6 Ib/cu ft; 1" thick;
0.5 Ib/sq ft 555554443
Laminated glass fiber (FRP); 0.375" thick 26 31 38 37 38
Walls—nonhomogeneous
Gypsum wallboard—two 1/2" sheets cemented together
joints wood battened; 1" thick; 4.5 Ib/sq ft 24 25 29 32 31 33 32 30 34
-------
(Continued)
Material or Structure Frequency (Hz)
125 175 250 350 500 700 1000 2000 4000
Gypsum wallboard—four 1/2" sheets cemented
together; fastened together with sheet metal
screws; dovetail-type joints paper taped;
2" thick; 8/9 Ib/sq ft 28 35 32 37 34 36 40 38 49
1/4" plywood glued to both sides of 1 x 3 studs
16 in. o.c.; 3" thick; 2.5 Ib/sq ft 16 16 18 20 26 27 28 37 33
f Same as above, but 1/2" gypsum wallboard nailed
no
""" to each face; 4" thick; 6/6 Ib/sq ft 26 34 33 40 39 44 46' 50 50
1/4" dense fiberboard on both sides of 2 x 4
wood studs, 16" o.c.; fiberboard joints at studs;
4/5" thick; 3.8 Ib/sq ft 16 19 22 32 28 33 38 50 52
Soft-type fiberboard (3/4") on both sides of
2x4 wood studs, 16" o.c.; fiberboard joints at
studs; 5" thick; 4.3 Ib/sq ft 21 18 21 27 31 32 38 49 53
1/2" gypsum wallboard on both sides of 2 x 4
wood studs, 16" o.c,; 4.5" thick; 5.9 Ib/sq ft 20 22 27 35 37 39 43 48 43
-------
(Continued)
Material or Structure Frequency (Hz)
125 175 250 350 500 700 1000 2000 4000
Two 3/8" gypsum wallboard sheets glued together
and applied to each side of 2 x 4 wood studs,
16" o.c.; 5" thick; 8.2 Ib/sq ft 27 24 31 35 40 42 46 53 48
2" glass fiber (3 Ib/cu ft) + lead vinyl compos-
ite; 0.87 Ib/sq ft 4 4 13 26 31
3/8" steel + 2.375" polyurethane foam (2 Ib/cu ft)
^ + 1/16" steel 38 52 55 64 77
ro
1X0 Same as above, but 2.5" glass fiber (3 Ib/cu ft)
instead of foam 37 51 56 65 76
1/4" steel + 1" polyurethane foam (2 Ib/cu ft) +
0.055" lead vinyl composite; 1.0 Ib/sq ft 38 45 57 56 67
Masonry
Reinforced concrete; 4" thick; 53 Ib/sq ft 37 33 36 44 45 50 52 60 67
Brick—common; 12" thick; 121 Ib/sq ft 45 49 44 52 53 54 59 60 61
3-3/4 x 4-7/8 x 8 glass brick; 3.75" th. 30 36 35 39 40 45 49 49 43
-------
(Continued)
I
ro
GO
Concrete bloc
01
•u
00
t-l
60
60
0)
-0
C
CJ
0)
i-t
5 a,
CO 4-1
CO
•O M
0) 0)
C Of
fl"
Material or Structure Frequency (Hz)
125 175 250 350 500 700 1000 2000
c — 4" hollow, no surface treatment 27 29 32 35 37 42 45 46
— 4" hollow, one coat resin — emul-
sion paint 30 33 34 36 41 45 50 55
— 4" hollow, one coat cement base
paint 37 40 43 45 46 49 54 56
— 6" hollow, no surface treatment 28 34 36 41 45 48 51 52
— 8" hollow, no surface treatment 18 24 28 34 37 39 40 42
— 8" hollow, one coat cement base
paint . 30 36 40 44 46 48 51 50
— 8" hollow, filled with vermic-
ulite insulators 20 29 33 36 38 38 40' 45
~— 4" hollow, no surface treatment 21 26 28 31 35 38 41 44
— 4" hollow, one coat resin-emul-
sion paint 26 30 32 34 37 42 43 46
— 4" hollow, two coats resin-emul-
sion paint 24 31 33 35 38 42 44 47
4000
48
53
55
47
40
41
47
43
44
44
-------
(Continued)
10
i
no
Material or
. Concrete bloc
CO
r-H
CO
CO
-a
CU
•X3
c
to
D.
X
W
cu
4J
CO
60
l-l
60
60
^C
0)
CO
60
cu
M
60
60
cu
CO
c
cu
Q
c— 4" hollow,
paint
—4" hollow,
paint
—6" hollow,
~— 4" hollow,
--4" hollow,
Structure
125 175
one coat cement-base
23 30
two coats cement-base
34 38
no surface treatment 22 27
no surface treatment 30 36
one coat cement base
paint on face 30 36
— 6" hollow,
—6" hollow,
sion paint
—8" hollow,
—8" hollow,
sion paint
no surface treatment 37 46
one coat resin-emul-
each face 37 50
no surface treatment 40 47
two coats resin— emul—
each face 38 50
Frequency
250 350 500
35 38
40 42
32 36
39 41
39 41
50 50
54 52
53 54
54 54
42
45
40
43
43
50
53
54
55
(Hz)
700
43
47
43
44
44
53
55
56
58
1000 2000 4000
44 48 43
49 51 46
46 45 43
47 54 50
47 54 49
56 56 46
57 56 46
58 58 50
60 38 49
-------
REFERENCES
1. Bragdon, C.R., Urban Planning and Noise Control, Sound and Vibration,
26-32, May, 1973.
2. Bugliarello, G., Alexandre, A., Barnes, J., and Wakstein, L., The
Impact of Noise Pollution. Pergamon Press, New York, 1976.
3. "Promoting Environmental Quality Through Urban Planning and Control,",
U.S. Environmental Protection Agency, Environmental Studies Division,
1973.
4. White, F.A., Our Acoustic Environment, John Wiley & Sons, New York, 1975.
5. Goodman, W.I., and Freund, E.C., Principles and Practices of Urban
Planning, International City Managers Association, Washington, D.C.,
1968.
6. National Environmental Policy Act of 1969, Public Law 91-190, 91st
Congress, January 1, 1970.
7. "Noise Abatement and Control: Departmental Policy Implementation
Responsibilities and Standards" Department of Housing and Urban
Development, Circular 1390.2, August 4, 1971 (amended September 1, 1971).
8. "Interim Noise Standards and Procedures for Implementing Section 109
(i) Title 23, U.S.C., " U.S. Department of Transportation, Federal
Highway Administration, Policy and Procedure Memorandum PPM90-2,
April 26, 1972.
9. Bragdon, C.R., Municipal Noise Ordinances, Sound and Vibration, 22-27,
December, 1976.
10. "Model Community Noise Control Ordinance," U.S. Environmental Protec-
tion Agency, September, 1975. EPA Document Number EPA-550/9-76-003.
11. "Information on Levels of Noise Requisite to Protect Public Health
and Welfare with an Adequate Margin of Safety," U.S. Environmental
Protection Agency, March, 1974, EPA Document Number 550/9-74-004.
12. Berandt, R.D., Corliss, E.R. and Ojalvo, M.S., Quieting: A
Practical Guide to Noise Control, NBS-Handbook #119, Washington,
D.C. U.S. Department of Commerce, 1976.
13. Berandt, R.D., E.L.R. Corliss, and M.S. Ojalvo, "Quieting: A
Practical Guide to Noise Control," National Bureau of Standards,
Report No. NBS HB-119, July 1976. Library of Congress 76-5500.
14. Peterson, A.P.G. and E.E. Gross, Jr., Handbook of Noise Measurement,
General Radio Co., Concord, Mass., Seventh Edition, Form No. 5301-
8111-K, 1972.
9-25
-------
15. Industrial Noise Manual, American Industrial Hygiene Association,
66 S. Miller Rd., Akron, Ohio 44313, 1975.
16. "Fundamentals and Abatement of Highway Traffic Noise, Vol. 1,
U.S. Dept. of Transportation, Federal Highway Administration, National
Highway Institute, June, 1973.
17. "Fundamentals and Abatement of Highway Traffic Noise, Vol. 2, Noise
Barrier Design and Example Abatement Measures, U.S. Dept. of Transpor-
tation, Federal Highway Administration National Highway Institute,
April, 1974.
18. "Fundamentals and Abatement of Highway Traffic Noise," Vol. 3,
Noise Prediction Charts and Sample Problem, U.S. Dept. of Transporta-
tion, Federal Highway Administration, National Highway Institute,
February, 1974.
19. Snow, C.H., "Highway Noise Barrier Selection, Design and Construction
Experiences -- A State of the Art Report - 1975," U.S. Department
of Transportation, Federal Highway Administration Implementation
Package 76-8.
9-26
-------
Chapter 10
SOUND SOURCE CHARACTERISTICS
Most outdoor sound sources may be placed under two broad classifica-
tions: 1) stationary sources and 2) transportation sources. A stationary
source is broadly defined as any source or combination of sources that
lies within legally defined boundaries, property lines, or zoning lines
as established by recorded deeds or other legal documents. This includes,
but is not limited to all machinery, vehicles, or other devices, whether
fixed or in motion, that are associated with the normal operation of
commercial, industrial, or residential land use. These sources remain
the recognized boundaries, property lines, or zoning lines. Some examples
of stationary sources are fans, blowers, compressors, refrigeration units,
cooling towers, power stations, bus and rail depots, cranes, derricks,
and trucks while being operated within the boundaries. A transportation
source is somewhat more obvious in that it can be considered as any source
that normally moves outside the aforementioned boundaries.
Both stationary sources and transportation sources share common
characteristics and can be defined and differentiated in terms of these
various characteristics.
10.1 Source Characteristics
A physical description of sound must include information on the
following parameters:
1) Level
2) Frequency distribution
3) Temporal distribution
4) Directional distribution
5) Operating conditions of the source
6) Description of measurement site and the location of
measurement point with respect to the source
All of these parameters must be considered carefully if an accurate descrip-
tion of the sound is to be provided.
10.1.1 Sound Level
The level or magnitude of a sound can be described in a number of
ways. It may be reported in terms of an overall sound pressure"level with
various frequency weightings, in octave, one-third octave, or narrower
frequency bands, or it may be reported in equivalent or statistical sound
pressure levels. Most sound level measuring instruments, such as the sound
level meter (discussed in the following chapter), are calibrated to provide
a reading in decibels (dB). The term "level" generally refers to a level (L
above a given pressure reference of 20 micropascals (yPa). Mathematically,
L is written: p.
p L = 20 log —- dB
M ^o
Chapter 2 should be consulted for additional details.
-------
10.1.2 Frequency Distribution
There are two basic ways to describe the frequency distribution or
spectrum of a sound. The first and most widely used procedure provides
a single overall sound pressure level measurement that includes a specified
overall frequency weighting. The specified frequency weighting emphasizes
some frequencies more than others in much the same manner as the human ear.
(1). The second way to describe frequency distribution is to measure the
sound pressure level in each of several contiguous frequency bands (2).
Obviously, the band-measurement procedure provides much more detailed infor-
mation than may be useful, or necessary, in cases 1) where the contribu-
tion of a specific source must be determined when several other sources
are also contributing to the sound, 2) when noise control actions must
be appraised, or 3) when a high percentage of the sound lies within
narrow frequency bands. However, this procedure is considerably more
complex and time-consuming than the single overall measurement, and the
additional complexity is not necessary in a very large majority of cases.
Therefore, this course will concentrate on the single overall sound pressure
level measurement procedures.
Several different overall frequency weightings have been established
for various purposes (1) but the so-called "A-weighting" is by far the
most widely accepted for evaluation of subjective and physiological effects
of sound. The A-weighting is specified for use in the rules and regulations
published by several Federal agencies including the Environmental Protec-
tion Agency (EPA), the Department of Labor (DOL), the Department of
Transportation (DOT), The National Institute of Occupational Safety and
Health (NIOSH), and the Department of Housing and Urban Development (DHUD).
The A-weighting is used for steady and intermittent sound evaluations but
not for short impulsive sounds. It is also used as the basic frequency
weighting for time averaging (Leq) or statistical (Ln) measurements, which
will be discussed in Chapter 11.
An advantage of a single overall frequency-weighted sound measurement
procedure is particularly obvious when rapidly varying sound levels are
to be measured. That is, a single measure of a varying sound can be
recorded in a relatively simple manner but very complex and expensive
equipment must be used to obtain instantaneous sound levels in several
continguous frequency bands.
Sounds that have a high concentration of energy in narrow frequency
bands (pitched or tone-like sounds) are usually regarded as more annoying
than wide-band sounds of the same level. Unfortunately, the single,
overall, frequency-weighted sound measurements do not reflect the addi-
tional annoyance of these pitched sounds. Therefore, if the objective of
the measurements is to measure annoyance it may be necessary to add about
5 dB to the measured values if a pitched sound is evident.
10.1.3 Temporal Distribution
The time or temporal variation in exposure to noise is of major
significance in predicting both physiological and psychological reactions
of humans to these exposures. Measurement methodologies use three broad
catagories of noise temporal patterns:
10-2
-------
1) Steady-State
2) Time-Varying/Fluctuating
3) Impulsive
Both the steady-state and the fluctuating categories can be divided into
continuous or intermittent patterns. That is, there can be continuous or
intermittent steady-state noises as well as continuous or intermittent
fluctuating noises.
. Steady-State Sound: The American National Standards Institute, ANSI,
defines a steady-state noise as "a noise whose sound pressure level remains
essentially constant (that is, the fluctuations are negligibly small)
during the period of observation". For the purposes of community noise
measurements it is convenient to use a maximum fluctuation limit of plus
or minus 3 dB to define steady-state noise. Hence, a steady-state noise
may be considered to be:
A noise whose A-weighted sound pressure level does
not fluctuate by more than plus or minus 3 dB about
a means, or a total fluctuation or no more than 6 dB,
when measured with the fast response of a sound level
meter.
Steady-State Continuous: A steady-state continuous sound has a
level that remains within 3 dB of its means, or has total fluctuations
of no more than 6 dB, throughout the observation period. Generally, any
device or facility that operates over periods of several hours and radiates
steady-state noise is considered as a steady-state continuous noise source.
Figure 10.1 shows one example of a steady-state continuous noise.
Steady-State Intermittent: A steady-state intermittent sound meets
the conditions for steady-state sounds, described earlier in the section
on Steady-State Noise, but operates in an intermittent, or on/off, manner.
The ANSI definition of intermittent noise is "a noise whose sound pressure
level equals the ambient level two or more times during the period of
observation." The period of time during which the level of sound remains
at an essentially constant value different from that of the ambient is on
the order of one second or more (3). Figure 11.2 shows an example of
steady-state intermittent noise.
Fluctuating Sound: The ANSI definition of a fluctuating noise is "a
noise whose sound pressure level varies significantly, but does not equal
the ambient level more than once during the period of observation". A
compatible definition with the specific numbers required for practical
application might be:
A noise whose A-weighted sound pressure level when
measured with the fast response on a sound level
meter fluctuates more than 6 dB but does not equal
the ambient level more than once during the period
of observation.
10-3
-------
10 DB
o
i
AMBIENT
1 F!IN
STEADY STATE CONTINUOUS SOUND
FIGURE 10,1
-------
.10 DB =3
o
en
AMBIENT
MIN*:
STEADY STATE INTERMITTENT SOUND
FIGURE 10 ,2
-------
Hactuating Continuous: As with the "steady-state continuous"
definition, a fluctuating sound exists over a long period of time and does
not drop to the ambient level more than once during the period of observa-
tion. Figure 10.3 illustrates such a sound. The determination of how
long an observation period must be to confirm that a sound is continuous
will depend upon a knowledge of the operating conditions of the source and
upon the ambient sound characteristics.
Fluctuating Intermittent: Obviously, a fluctuating intermittent
sound does not meet the criterion of continuous sound. A sound level
that drops to the ambient sound level more than once during the period
of observation and has fluctuations is excess of 6 dB can be considered
as fluctuating intermittent sound. Again, knowledge of the source operating
conditions and of the ambient sound characteristics will determine the
necessary period of observation. Figure 10.4 shows an example of a
fluctuating intermittent sound.
Impulsive Sounds: Generally, an impulsive sound occurs over such a
short time period that sound level meters cannot respond fast enough to
provide an accurate measurement of level. An exception to this generaliza-
tion is a series of ten or more impulses occurring within one second.
Then a sound level meter can be used to provide a reasonably accurate
assessment of level.
There are several factors that are used to describe an impulsive
sound. These factors include: 1) the time necessary to reach a peak
sound pressure level (rise time). 2) the peak sound pressure level
(not A-weighted), 3) the time elapsed after the peak pressure is reached
for the pressure level to fall a specified number of decibels, and 4)
the amount of reflected sound energy that is received.
10.1.4 Directional Distribution
The directional characteristics of a sound source must be considered
in order to use the sound measurement equipment properly. For example,
a free-field type microphone must be pointed toward the sound source and
a pressure type microphone must be directed so that the sound grazes its
diaphragm in order for them to perform as calibrated.
Directional characteristics of sound may also be used to pinpoint
major contributors to sounds that have many different sources. A direc-
tional microphone, one with a narrow beam of sensitivity, is often useful
in pinpointing major sources for noise control work.
There is a particular need for a complete and accurate description
of sound sources measured at a particular location especially when
these measurements are to be repeated and compared at some future time.
For example, before and after measurements may be required to determine
the effectiveness of noise control procedures. Also, sound levels produced
at a particular location at different hours of the day or night must be
compared. In any of these situations it is very important to precisely
and completely describe the characteristics of the source.
10-6
-------
10 oB
o
I
AMBIENT;
FLUCTUATING CONTINUOUS SOUND
FIGURE 10,3
-------
10 DB
o
i
oo
AMBIENT
FLUCTUATING INTERMITTENT SOUND
FIGURE
-------
Some of the common descriptive factors for sound sources are:
1) Physical description and purpose
2) Are housing or shock mounts used?
3) Power rating
4) Speed of operation
5) Characteristics of other sources that may contribute to
the overall level.
10.1.5 Source Operating Conditions
The conditions under which the sound source is operating at the time
of measurement must be specified if noise measurement data are to have
practical meaning.
10.1.6 Description of the Measurement Site
A complete description of the measurement site must be provided along
with a description of the source or sources in order to make sound measure-
ments meaningful. Various building surfaces, walls, trees, large signs
and other surfaces may either reduce, or increase, the amount of sound at
given locations by blocking or reflecting sound coming from the source or
sources. Therefore, it is important to describe the exact positions of
the sound sources and any potential sound barriers or reflectors with
respect to the measurement locations.
Generally, it is not necessary to make adjustments for sound barriers
or reflectors if measurements are to be repeated in precisely the same
location. That is, the measurements are being conducted for the purpose
of comparing the levels and not for obtaining absolute levels at that
location. If the measurement data are to be used for purposes where
absolute levels with the highest possible accuracy are required (i.e. for
ordinance enforcement) then it may be necessary to use adjustment factors
when measurements must be made close to walls or in other locations where
the sound levels may be altered significantly by environmental factors
(see Chapter 8).
Consideration must also be given to weather conditions when absolute
accuracy in sound .measurement is required. Adjustments for various weather
conditions are difficult, if not impossible, so repeated measurements may
be required at times when weather conditions are suitable (see Chapter 8).
10-9
-------
REFERENCES
3.
American National Standard Specification for Sound Level Meters,
SI.4 - 1971, American National Standards Institute, Inc., 1430
Broadway, New York, N.Y. 10018.
American National Standard Specification for Octave, Half-Octave,
and Third-Octave Filter Sets, SI.11 - 1971, American National
Standards Institute, Inc., 1430 Broadway, New York, N.Y. 10018.
American National Standard Methods for the Measurement of Sound
Pressure Levels, SI.13 - 1971, American National Standards
Institute, Inc., 1430 Broadway, New York, N.Y. 10018.'
10-10
-------
Chapter 11
INSTRUMENTATION AND MEASUREMENT METHODOLOGY
Community definitive noise ordinances are written in terms of the
maximum allowable sound level permitted in most cases. Various measure-
ments have been developed to express these limits. Those measures most
commonly used in community noise assessment include the statistical dis-
tribution of noise levels (L^), the,Energy Equivalent Continuous Level
(Leq) and the Day-Night Level (LDN). Nhatever the descriptor of the
allowable noise level, a specified type of instrumentation is required
to measure the sound levels, and a specified procedure must be followed
to produce the descriptor. In this chapter, the instrumentation and basic
noise measurement techniques will be discussed as well as the procedural
steps required to obtain specified descriptors.
11.1 Sound Level Meters
The sound level meter (SLM) is the basic instrument for measuring the
overall sound pressure level of continuous or fluctuating kinds of sounds.
A sound level meter consists of a microphone, calibrated amplifier-
attenuator circuits, frequency weighting networks, and an indicating meter.
The microphone transforms the acoustic signal received at its diaphragm
to an equivalent electrical signal with the same frequency and amplitude
characteristics. The weighting networks modify the frequency spectrum of
the electrical signal with selective characteristics patterned after those
of the human ear. This frequency weighting therefore provides the means
whereby the measured level of the sound may be correleated to the perceived
level. The carefully calibrated amplifier-attenuator circuits provide a
regulated level of signal to the indicating meter where the sound level
is displayed in decibels.
The operational characteristics of a sound level meter are specified
by both national and international standards. The American National .
Standards Institute, ANSI SI.4 -1971 "Specifications for Sound Level
Meters" provide the maximum allowable tolerances used for most applications
in the USA, and for the two types of sound level meters (Percision Type 1,
and General Purpose Type 2) recommended for community noise measurements.
Many additional nosie measures that may be applicable in a community
setting have been developed. Such additional criteria for rating
sounds are included in the Handbook for Regional Noise Programs (1).
-------
11.1.1 Weighting Networks
Sound level meter frequency weighting networks are used to determine
roughly how sound energy is distributed with frequency. These weighting
networks also may be used to provide a closer correlation between the
sound measurements and human response to the sound. In community noise
measurements the most often used A-weighting gives good correlation with
human response. Differences between the A-weighted and C-weighted (or
flat-weighted) levels will afford a good approximation of the ratio of
high to low frequency distribution of the sound.
The ideal A-, B-, and C- frequency weightings, relative to a flat
or overall frequency response, as specified by ANSI SI.4 -1971 are shown
in Figure 11.1 Tolerances may be found in the Specifications. A D-
weighting network which emphasizes frequencies between 1000 and 10,000 Hz
is included in certain foreign sound level meters and is used primarily
for noise measurements around airports.
11.1.2 Meter Indication and Response
The indicating meter or readout of the SLM must have a scale covering
a range of at least 15 dB. The accuracy of the scale gradations must
be at least ± 0.2 dB except in the lower part of the scale that is
overlapped by a change in attenuator setting where the accuracy require-
ment is ± 0.5 dB. The response time of the indicator (gennerally measured
as the response time of the complete SLM) must be in accordance with the
"Fast" or "Slow" dynamic characteristics specified. The Fast response
specifications require the meter to be within 0 to 4 dB less than the
correct reading for a Type 2 instrument and 0 to 2 dB less than the correct
reading for a Type 1 instrument for a 1000 Hz signal with a duration of
200 milliseconds. The slow response specifications require the meter to
be within 2 to 6 dB less than the correct reading for a Type 2 instru-
ment and 3 to 5 dB less than the correct reading for a Type 1 instrument
for a 1000 Hz signal with a duration of 500 milliseconds.
If sound level fluctuations are rapid but of a duration of 500
milliseconds or longer, the SLM may be used with reliable accuracy. With
the exception of impulsive sounds, most community noises may be measured
with the fast or slow meter characteristics. Fast meter characteristics
should be used wherever possible for the greatest accuracy; however, when
the sound levels are fluctuating rapidly, it may be necessary to use the
slow meter characteristics in order to get reproducible readings. The
slow response averages the sound input so that there are smaller ranges
of level change and the rates of change are reduced so that the meter can
be read more accurately. The slow response is particularly useful when
widely fluctuating sound levels are to be compared from, one time to
another (i.e. before and after noise control measures).
When impulsive sounds such as those from gun shots, pile drivers,
drop forges, or jack hammers, are encountered, an oscilloscope or an
impulsive-type SLM must be used (2,3,4). Impulsive sounds are considered
to be those whose sound pressure levels rise above the ambient by 10 dB
or more in a time less than 0.2 second. The measuring instrument must be
11-2
-------
+10
PQ
a
•H
-------
capable of reading the peak sound pressure level (unweighted). If an
impulsive-type SLM is used, it should include a peak detector and holding
circuitry so that the peak level is held long enough to be read or until
manually reset. Peak sound pressure levels should be recorded for at
least 10 impulses in close succession so that a numerical average level
can be determined. Generally, the average, the highest, and the range
of impulsive levels should be recorded. Extreme care must be taken to
follow the instrument manufacturer's instructions if accurate impulse
sound level data are to be obtained.
11.1.3 Microphones
Each type o'f microphone has advantage and disadvantages that depend
upon the specific measurement requirements. Calibration and frequency-
response curves and stability characteristics with respect to temperature,
humidity, vibration, and electromagnetic fields are generally available
from the instrument manufacturer. Performance limitations for the
microphone system may be found for Types 1 and 2 sound level meters in
ANSI SI. 4 -1971.
Orientation: Some microphones are calibrated to perform correctly
when sound approaches perpendicular to the diaphragm (0°), while others
are calibrated for grazing incidence (90°), or for random incidence.
Figure 11.2 shows the microphone response for these different angles of
incidence. All of these microphones must be oriented as they are calibrated
otherwise errors will result that will be particularly prominent at high
frequencies. The preferred height of the microphone above the gound or
supporting surface is 1.2 meters (4 feet), although any height between 0.6
and 1.8 meters (2 and 6 feet) is acceptable for specific measurement con-
ditions. A record of microphone position should be carefully documented,
preferably on a plan view of the measurement site so that measurements can
be repeated at a later date if necessary (see Figure 13.I)2.
The choice of a microphone may depend upon several factors that will
include the location of the sound source. If the sound is coming from a
particular fixed direction, a microphone calibrated at perpendicular
incidence (free field type) may be selected because it will discriminate
against potential masking noises coming from other directions and generally
it will have very good high frequency response characteristics, if, on the
other hand, the source is in motion, such as in the case of a vehicle
traveling on a road, a microphone calibrated for grazing incidence (pressure-
type) may be preferred because it can be mounted in a fixed positions pointing
upward and receive the sound at grazing incidence as the vehicle moves.
The microphone calibrated for random incidence is generally a good choice
for measurements in a diffuse sound field where the sound is coming from all
directions. These microphones may be used interchangeably in most situations
but the manufacturer's instructions must be followed on orientation in each
situation or errors will result.
2
Additional calibration data should be recorded when using the SLM in a
noise survey. Figure 13.1, the Community Noise Survey Data Sheet, pro-
vides a simple form for such record keeping. The appropriate procedure
for completing this data sheet will be discussed in Chapter 13.
11-4
-------
dB 20
10
-10
-20
1
1
•
1
—
•-
i
—
'
•
r -^
a
iq
. --* —
i
I
—
—
—
—
. — r
— i
—
'-i
r.
...
i
_
-
•
-
mt^^
^^•Ml
FREE FIELD RESPONSE OF A 1" PRESSURE
MICROPHONE FOR VARIOUS ANGLES OF
INCIDENCE,
jge^H
m^
|JiB
ar^
X\/9
1
!
j
^e-H
HM^^>H|
L —
^•e
,
i 1
.
•
r —
|
t
^^^
SSe
\^5
^
^^
£
^
^.
0
'
=a
1
|
I
t
^
•^
M
•-
«
r 1
\ \
1-
j
"
i
^/
|
V ' 1
X
~\
>
90
k.
\
\
\
o
i
10
90 Hz 50
100
200
500
1000 2000
5000 10000 20000 40000
Figure 11.2
-------
Temperature and Humidity: Most modern microphones are not permanently
damaged by normal ranges of temperature and humidity. However, temporary
erroneous readings may result from condensation if the microphones are
moved from very cold to very warm areas. To avoid errors from condensation,
the instruments should be turned on and allowed to sit in the measurement
area for at least five minutes prior to making measurements. Temperature
and humidity correction curves are generally supplied with the microphone
and should be consulted.
Microphone Cables: In most community noise assessment situations,
sound level measurements should be made with the microphone mounted on
the sound level meter. However, there are special situations where an
operator's body, or even the instrument case, should be removed from the
measurement area in order to obtain accurate data. In most cases where
cables are required the sound has a high proportion of its energy concen-
trated in high frequencies (above 1000 Hz). The higher the frequencies
of major sound components the more likely it is that there will be errors
introduced as the result of reflection from the operator's body or from
the instrument case.
When extension cables are required for microphones, care must be taken
to make the necessary corrections to the sound level reading according to
the instrument manufacturer's instructions. Some microphones require
special electronic circuitry when used with cables and others do not. The
amount of correction for given lengths of cable also varies from one instru-
ment system to another. Therefore, the manufacturer's instructions should
be followed precisely if accurate data are to be obtained. Finally, the
microphone must always be calibrated while it is mounted on the cable before
and after it is used.
Windscreen: Rapid air movement over a microphone causes turbulence
that in turn generates extraneous noise. This noise can effectively mask
the sound being measured and cause erroneous high level readings. The use
of earphones connected to the SLM output jack (consult manufacturer's
recommendations) often will enable the operator to detect wind generated
noise; however, low level masking may occur that will be inaudible. There-
fore, it is good practice to use microphone windscreens in any case when
wind or wind gusts are suspected during the course of measurements.
Generally, windscreens are either spherical or cylindrical shaped
framed polyvinyl, open-celled polyurthane, or silk-covered grids. The
windscreens are attached directly over the microphone so that the effects
of wind are reduced. However, there are limits to their effectiveness.
Three rules of thumb are:
1) measurements should never be made, even with windscreens,
in winds having velocities greater than 20 km/hr (12 mph);
2) measurements should not be made if wind noise is audible
though a monitoring headset connected to a SLM when using
the A-weighted and the lowest attenuator setting (setting
for measuring the lowest sound level to be measured); and
3) measurements may be made utilizing a windscreen and an
octave, or narrower, band analyzer as long as it can be
determined that the wind noise remains at least 10 decibels
below the sound being measured in any of the frequency
bands.
11-6
-------
In all cases, the windscreen should be one provided by the SLM manu-
facturer for that instrument. Corrections should be available for these
windscreens. If such a windscreen is not available, if no corrections are
available for a windscreen, or if a windscreen is old or soiled, tests
should be made by presenting reproducible sounds to the microphone with
and without the windscreen in place. The test sounds used should contain
low, median, and high frequency components (i.e. 500, 1000, 2000, 4000, and
8000 Hz). In particular, the windscreen should be tested with similar
frequency components to those expected from the sounds to be measured.
Corrections should be developed and used for differences up to 2 dB. If
the windscreen causes changes greater than 2 dB, the windscreen should be
discarded-.
Calibration: There are two kinds of instrument calibration procedures
that must be used if accurate measurements are to be obtained. A
laboratory calibration should be performed at regular intervals not wider
spaced than 1 year. 'These calibrations should be done by qualified personnel
such as the instrument manufacturer or acoustical laboratories. Equally
important fielld calibrations should be made before and after each use of
the measurement equipment. Field calibrations are conducted with acoustic
calibrators provided by the instrument manufacturers.
Generally, the field calibrators are compact, battery operated devices
that provide a means for conducting an overall-system calibration check.
Some calibrators generate a single frequency and others provide several
different test signals, all at specified sound pressure levels. Field
calibrators are designed to be used on .specific microphones and they should
be used only on these microphones. Otherwise, errors may result or micro-
phones may be permanently damaged.
In use, the sound level generated by the calibrator should correspond
to the SLM reading. If it does not, the instrument instruction book must
be consulted to determine how adjustments are to be made. All calibrations
should be made using the Flat- or C-weighting settings on the SLM unless
otherwise specified by the manufacturer. As a secondary check on the per-
formance of the A-weighting, the difference in levels between SLM reading
and the calibrator level may be compared with the specified A-weighted
relative response at each test frequency (see Figure 11.1).
Caution should be exercised when using calibrators at atmospheric
pressures different from that at sea level. Normally, correction data are
supplied by the instrument manufacturers.
11.2 Statistical Analysis of SLM Data
Various kinds of statistical analyses are used in noise ordinances
as a means of evaluating sound exposure levels. A statistical analysis
can be applied to any sound exposure pattern whether it is steady, inter-
mittent, fluctuating, impulsive or a combination of these temporal patterns.
Only a very simple temporal analysis is necessary to describe steady or
long term intermittent sounds; however, more complex statistical procedures
are required to describe sounds that have rapidly varying levels. Manual
and automatic statistical sampling and analysis procedures are available
for field and laboratory purposes. Manual sampling, which is discussed
below, requires the least expenditure for equipment but requires
the presence of a data taker.
11-7
-------
Automatic sampling equipment is desirable for extensive long-term
sampling because it does not require an operator to be present; however,
it is generally much more expensive and it is more complicated to cali-
brate and maintain. Details on automatic sampling equipment can be
found in instrument manufacturer's literature.
11.2.1 Manual Sampling Procedures
Determination of Statistical Distribution of Noise Levels (L..)
Statistical distribution of noise levels makes use of sound pressure
level measurements taken at predetermined time intervals over some
specified observation period. From these data the percentage of time
that any specified sound level is exceeded can be determined. Alternately,
the sound level that is exceeded a specified percentage of the observation
time such as l_io» LSQ, and LQQ, which are the percentile levels exceeded
10, 50, and 90 percent of the observation time, can be determined. The
most common percentile level used to describe community sounds is the LIQ-
The 1.50 is gennerally taken as the mean level while Lgg is taken as the
ambient (background) level.
The length of the observation period must be adequate to describe
the variation in sound level. A rule-of-thumb for determining the required
period of observation is that the time period should be long enough to
accumulate at least a number of samples equal to 10 times the total sound
level fluctuatiton. For example, if the sound levels fluctuate over a
range of 14 dB (± 7 dB), the total number of samples should be in excess
of 140. The total time in which the samples are taken depends upon the
interval between samples and the sample time. From previous studies
(5,6,7) it has been determined that a sampling rate of once every ten
seconds yields a 95 percent confidence limit3. In other words, the L-JQ
value will be within ±3 dB of the correct value for this sampling rate.
For the example given above, the total observation time necessary to take
140 samples will be about 23 minutes.
Equipment: The basic equipment required for manual sampling is a
sound level meter, a timing device, and a data sheet (see Figure 11.3).
The timing device may be a watch with a second hand, or an automatic timer
with an audible or visual indicator that can be set to various time intervals.
A small tape recorder also may be desirable by some operators to
describe source and measurement conditions (not for recording the sound
being measured). Care should be taken to prevent verbal communications
between the operator and the recorder from being picked up by the SLM
microphone during measurements.
The mathematically correct procedure for determining the error associated
with a sampling method is to have the sample spaced randomly in time.
However, this is inconvenient for'field measurements. An equally correct
error analysis can be performed if the samples are regularly spaced, but
the signal varies randomly in time. This is the approach taken here.
11-8
-------
SOUND LEVEL METER TYPE^
STARTING TiMsZlcc AM _ P
SAMPLING INTERVAL /^- St-c
SERIAL
PRIMARY NOISE SOURCE.
SECONDARY NOISE SOURCE ~7~ra,
COMMENTS
TOTAL OBSERVATION TIME
I 2 3
H-
OP
(D
_9
18
"A
j
4
"311 _
_. _i_:_i____J
j • : ! i
I ,' ' i I
n
o
n>
5
ca
>
LJ
3. i ?
CO
I
"izrn
1 11
i i
_L
L! J_ i J_L
' !_UJ.
l-l/
_i..i^4J.44_U_|_L
CO
UT
n>
n>
n-
TO
: 6
Lis
_ 4
_"3
L 2
66
•"- "• •'•.*'*
K F K V li'T"
i/i I'lfjU
~&r~\
IS
\/\ IS\ IT
if;t
fU-i
4-
(/
-4-4-
I ' I
TT
! •
1
I
4--L-
! I
i I !
JZJO i I I ' I i I I 50
=R--
—rH—^~;-
JT !_!_!_.
1~*TT
.4_L4—•
! i I 1
4±±
_1_
-J-|4 -U
-P-4-1
Mi I
i
-f
.--I-
oi±
n i i
I ! I
i i i
4-
_
5C
2..
2-
10
~V
L^_
/fc
30
?8_
2-2.
12.
~
12.
71
111
2.W
T~
z;
'2.
n~
i-SL
31
re
82
NUMBER OF OCCURANCES
-\ o
•— Tt
O
- C3
^ 5
^ ^>
S~^
'V m
m
^
-------
Procedure: The procedure for determining the statistical distribution
and the corresponding L,0 and Lgn values is as follows:
1) Check the battery of the SLM and other battery operated
equipment
2) Check the calibration of the SLM according to the instrument
manufacturer's instructions (also see Section 11.1.3)
3) Consult the SLM manufacturer's instructions and Section 11.1
to determine proper operation procedures.
4) Locate the SLM microphone at the point of interest
5) Set the SLM weighting switch to the "A" position and the
meter response switch to the "Fast" position.
6) Turn the SLM ON and observe the range of the meter fluctua-
tions. Multiply this range by 10 to compute the total
number of samples required. (If this range increases
during the course of taking data, the number of samples
required will also increase; however, the number of samples
required is not changed if the fluctuation range decreases)
7) Every 10 seconds read the instantaneous A-weighted sound
level and record this level as an occurence by making a
check in the appropriate row of the data sheet (see Figure
11.3). Work from left to right within each row as sample
levels reoccur.
8) After the appropriate number of samples have been taken, add
the number of check marks in each row and record this number
in column one of the data sheet (see Figure 11.3).
9) Add the row totals in column one beginning with the highest
sound pressure level total (top figures) and record these
numbers in column two (i.e. from the top of column 2,
4=4, 4+2=6, 4+2+2=8, etc).
10) Divide each number in column two by the total number of
occurences (bottom number in column 2) and multiply by
100 (i.e. (4f242)xlOO, (6;242)xlOO, etc). Enter these
numbers in column three.
The numbers in column 3 are percent!les for each sound level that
correspond with the percentage of time that the sound level was exceeded.
In the work sheet example, 80 dB was exceeded 7 percent of the time and
78.5 dB was exceeded 10 percent of the time (i.e. L10=78.5 dB(A), L50=?0.0 dB(A)
Lgn = 54.8 dB(A)). These percentile determinations are accurate within ±3 dB.
Determination of the Energy Equivalent Continuous Level (L )
An energy equivalent continuous level, Leq, is another effective means
for describing sounds with fluctuating levels. By definition, Leq is the
level of a steady-state continuous sound having the same energy as the
actual time varying sound. In other words, Leq is numerically equal to
the continuous dB(A) level that has the same sound energy content as the
actual fluctuating sound (over a given observation period). Leq accounts
for both duration and level of all sounds occurring during a given obser-
vation time period. Since Leg is related to energy (rather than pressure)
averaging it emphasizes the higher sound levels, and thus it does afford
a good measure of high level intrusive noises.
11-10
-------
In most cases, the L has been found to be an acceptable and simple
sound rating for assessment of annoyance. However, it is not as good as
the more flexible cumulative sound descriptors, L|\| (L-jo> 1-50' Lgg) for
special cases such as those in which moderately high, almost continuous
levels may be more annoying than intermittent higher level noises that
have short durations.
Another characteristic of the Leq is that it responds to changes in
the sound duration or level much more steadily and continuously than the
LN statistical numbers. Obviously, in any case where there is doubt
about the choice of measuring procedure, it is advisable to use both the
L and L,. descriptors.
As with the statistical L|\| descriptors, the Le can be determined by
either manula or automatic means. A convenient metnod of calculating Leq
from LCQ and L]g values is possible for sounds that have a Gaussian
distribution (8). The formula is as follows:
If L5Q = 74 dB(A) and LIQ = 81 dB(A)
L = 74 + 0.07 (81 - 74)2. = 77.4 dB(A)
Day-Night Level (LpN)
is a noise measure that gives greater weight to night time noises.
It is the 24 hour Leq level with a 10 dB night time penalty added to the
noise levels between 10 p.m. and 7 a.m. Thus, this measure takes into
consideration the greater intrusiveness of night time noises.
11.3 Sound Analyzers
Adequate assessment of community noise is provided in most cases by
sound level meters. However, in a few cases where most of the sound energy
is concentrated within narrow frequency bands, additional information may
be required. Additional information is particularly useful when 1) it is
necessary to determine which one of several contributing sources is the
principal contributor, or 2) when noise control measures are to be
selected or evaluated.
Basically, a frequency analyzer is an electronic filter that
selectively passes on those signals having frequency components for which
it is tuned. Thus, an analyzer makes it possible to read the sound pressure
levels contributed by those frequencies selected by the analyzer.
Two basic analyzers of primary concern for community noise measurements
are the octave- and the one-third octave-band analyzers. These analyzers
may be an integral part of a sound level meter system or they may be
separate units that must be attached to separate readout devices. In any
case, instructions from the manufacturer must be followed carefully.
11-11
-------
11.3.1 Octave-Band Analyzers
Octaves are the most common bandwidths found in sound analyzers.
Octave bandwidths are the widest bands used; thus, they provide an
analysis with a minimum number of measurements.
An octave band is defined as any bandwidth having an upper band-
edge frequency, f2, equal to twice the lower band-edge frequency, f-j.
In other words, f2=2f-|. The center frequency, fc, (geometric mean) of
an octave band is equal to the square root of the product of the upper and
lower band-edge frequencies fc=/f-|f2). ANSI preferred center frequencies
(31.5, 63, 125, 250, 500, 1000, 2600, 4000, 8000, 16,000 Hz) are used to
specify the various octave bands (9). For example, 100 Hz is center
frequency of the octave band with band-edge frequencies f]=71 and f2=142 Hz.
Also, 1000 Hz is the center frequency for the band-edge frequencies
f1=707 and f2=1414 Hz, and 10,000 Hz is the center frequency for the band-
edge frequencies fi=7070 and f2=14,140 Hz. Figure 11.4 provides an example
of a Noise Survey Data Sheet designed for recording octave band data^
Tolerances for octave analyzers are specified by ANSI SI.11 -1966.
Either Class I or Class II instruments described in this Standard are
acceptable for community sound measurements.
11.3.2 One-Third Octave-Band Analyzers
When more precise information on the sound pressure spectral distribu-
tion is required than can be extracted with octave-band analyzers, the
next step is one-third octave-band analyzers. As the name implies, a
one-third octave bands.
The upper band-edge frequency of a one-third octave-bandwidth is
determined by multiplying the lower band-edge frequency by 3/2T The
lower band-edge is 0.891 times the center frequency which is selected
from the preferred frequencies as with the octave bands' center frequencies
(9). Performance standards for one-third octave band analyzers are also
given by ANSI SI.11 -1966.
11.3.3 Statistical Analyzers
Sounds with fluctuating levels are extremely difficult to measure and
to describe in a meaningful way. One effective way to perform this diffi-
cult task is to use statistical analysis techniques as discussed earlier
in this chapter. Statistical analyzers make this task easier by perform-
ing many of the operations automatically.
Basically, statistical analyzers are instruments that measure sound
pressure levels at fixed intervals of time and store this information.
In most instruments various levels are stored as events each time they
occur. Generally, the event registers are calibrated in one, two, or five
decibel increments over a range of 50 to 100 decibels. The sampling rate,
or the interval between event measurements is generally selectable from
11-12
-------
'N OTSE
A HT S
DATE
LOCATION
OCTAVE BAND
(Center Freq. )
Over all -Linear
A-Frequency
Weighting
31 Hz
62 Hz
± 125 Hz
^ 250 Hz
500 Hz
1000 Hz
2000 Hz -
4000 Hz
8000 Hz
Taken By:
DECIBELS
Time-
Remarks:
Figure 1
DECIBELS
Time-
Remarks:
1 . 4 Noise Su
DECIBELS
Time-
Remarks:
rvey Data She
DECIBELS
Time-
Remarks:
2t for Record]
DECIBELS
Time-
Remarks:
,ng Octave-Ban
DECIBELS
Time- ' .
Remarks:
d Data,
Sound Measuring
Equipment:
Type
TwToHel $
.qpt-rai ^
i ype
IWnHel #
Serial #
OCTAVE BAND
(Center Freq. )
Over all -Linear
A-Frequency
Weighting
31 Hz
62 Hz
125 Hz
250 Hz
500 Hz
1000 Hz
2000 Hz
4000 Hz
8000 Hz
FIELD
CALIBRATION
Cal. Type
Tir-ne
Freq. , Hz dB
!?<;
7sn
£nn
1000. .
?nnn
-------
0.1. to 10 samples per second for any preselected observation period up to
24 hours. At the end of the observation period the registers may read out
in terms of total number of occurances in each level register or in terms
of the decibel level exceeded for a given percentage of the observation
time.
The accuracy of the statistical data obtained from such an analysis
depends upon the sampling rate and the spread in level (decibels) between
registers. The higher the sampling rate and the smaller the spread
between registers, the greater the accuracy.
Statistical distribution analyzers are expensive and they may not
always be available. Mhen they are not available, these data may be
obtained with the manual procedures using sound level meters as described
in section 11.2.
11.4 Tape Recorders
For special cases, it may be convenient to record a sound so that an
analysis may be made at a later date. A tape recording is particularly
helpful when a series of analyses are required or when the sound source
is on for only a short period of time. Extreme care must be taken,
however, in the use of tape recorders. Tape recorders are difficult.to
calibrate and to use so this work should be left to highly qualified pro-
fessionals whenever possible.
Obviously, when a tape recorder is used, the manufacturer's instruc-
tions must be followed closely. Also, the specifications of the tape
recorder should be studied closely to determine if it will provide the
required frequency range and overall accuracy. It is strongly recommended
that "instrumentation-type" recorders be used (rather than the less
expensive "audio-type") because of their tight tolerances, their long-
term stability, and the convenience of calibration and use.
11-14
-------
REFERENCES
1. "Handbook for Regional Noise Program," Office of Noise Abatement and
Control, Washington, D.C. 20460, April, 1974, EPA Document Number
550/9-74-006.
2. Peterson, A.P.G. and Ervin, E.G., Jr., Handbook of Noise Measurement
General Radio Co., Concord, Mass, Seventh Edition, Form No. 5301-8111-K
1972.
3. Brock, J.T., Acoustic Noise Measurements, Bruel & Kjaer, 1975.
4. Sataloff, J. and Michael, P.L., Hearing Conservation, Charles C.
Thomas, publisher, 1973.
5. Safeer, H.B., Wesler, J.E., and Ricley, E.J., Errors Due to Sampling
in Community Noise Level Distribution," J. Sound Vib, 2^, (3), 365-376,.
1972.
6. Verges, J.F. and J. Bellinger, Manual Traffic Noise Sampling -- Can
it be Done Accurately? Sound and Vibration, 23-30, December, 1973.
7. "Fundamentals and Abatement of Highway Traffic Noise," Report prepared
by Bolt, Beranek and Newman, Inc. for U.S. Dept. of Transportation,
Federal Highway Administration, under contract No. DOT-FH-11-7976, June,
1973. Available from National Technical Information Service, Spring-
field.. VA 22151 (PB-222 703).
8. Unpublished work, Michael, P.L., M. Oslac, R. Kerlin, J. Prout,
"Development of Measurement Methodologies for Stationary.Sources,"
Contract No. 68-01-3304, U.S. Environmental Protection Agency, Office
of Noise Abatement and .Control, Washington, D.C. 20460.
9. American National Standards Institute Preferred Frequencies and Band
Numbers for Acoustical Measurements, ANSI SI.6 -1967.
11-15
-------
Chapter 12
COMMUNITY NOISE ATTITUDE SURVEYS
The complete assessment of a community noise problem usually requires
the collection and analysis of attitudinal data. Such data should be
collected in conjunction with the actual measurement of noise levels in
the environment. The purpose of this chapter is to discuss the major
aspects of community noise attitude surveys. Several of the major meth-
odological aspects of survey design will be addressed and recommendations
will be made regarding information that should be obtained in a community
noise survey.
Traditionally, attitudes have been defined as tendencies to respond
either positively or negatively to certain persons, or situations. The
word noise, then by its very definition as unwanted sound, implies a
negative attitude with respect to certain sounds. Research to date provides
convincing evidence that people's values, beliefs, and attitudes heavily
influence their response to noise (1). Some researchers go so far as to
say that these variables are at least as important for predicting annoyance
from noise as the actual physical properties of the noise per se (2).
It is evident, then, that in many cases the impact of noise on a community
cannot be adequately assessed by sound pressure level measurements alone.
These measurements must be supplemented with attitudinal survey data to
include the subjective elements.
12.1 Surveys and Survey Instruments (Interviews and Questionnaires)
The terms survey, interview, and questionnaire are often used inter-
changeably. However, these terms are not synonymous and should be dis-
tinguished from each other. The term survey refers to the general act
of acquiring information. It does not refer to an actual method or
instrument used for such purpose. Interviews and questionnaires, on the
other hand, are two popular ways to collect information; thus, they are
two survey instruments. Attitudes then may be surveyed through the use
of interviews or questionnaires.
An interview is usually a face-to-face session where the interviewer
.asks some selected individual (usually called the respondent) a series of
questions about the topic of concern. Interviews that involve straight-
forward questions and answers about topics that are not highly personal
or emotional can often be handled on the telephone. Such interviews reduce
the time and costs involved in a face-to-face format.
When it is not feasible to use a face-to-face format a written
questionnaire is often useful. A questionnaire usually consist of a
printed set of questions that is distributed to a respondent. The respon-
dent completes the questions and returns the form, often by mail, to the
individual or group doing the survey. Since the individuals read and
answer the questions themselves, questionnaires are often referred to as
being self-administered.
-------
Part of the confusion in the use of the terms interview and question-
naire is attributable to the fact that many interview situations make use
of interview protocols or schedules. These forms resemble questionnaires
in that they contain the questions and response formats that will comprise
the interview. The interviewer uses this form as an outline from which
to administer the interview, and as a form to record the responses. The
use of detailed protocols insures that all respondents receive the same
questions in the same approximate order.
There are certain advantages in employing interviews rather than
questionnaires. In an interview, questions can be explained, unexpected
responses can be interpretated, and more in depth questions can be
included. On the other hand, questionnaires are usually less expensive.
Also, people tend not to fill out or return questionnaires.
12.2 Sampling
Interviews and questionnaires are data or information collecting
strategies. These techniques are usually employed in a situation where
an investigator wishes to be able to make statements about some defined
group of people, such as for example, those persons residing within a
five mile radius of a large airport. Usually it is not feasible to inter-
view all of the people that comprise the group or population of interest,
so a representative sample of these individuals must be selected. A
representative sample provides a reasonably accurate representation of
the characteristics of the total population. Thus, the findings based on
a representative sample of the population are likely to correspond closely
to those that would be obtained if the total population were studied. The
generalizability of the results of even the best designed interview or
questionnaire will be reduced if careful attention is not paid to sample
selection.
A basic distinction exists in modern sampling theory between pro-
bability and nonprobability samples (3). A probability sample, or one of
its variants, is necessary in order to insure a representative sample.
Non-probability samples should be avoided where possible. For example,
it might be convenient to administer a questionnaire to persons attending
a citizen's group meeting, but such a non-probability sample group would
not be a dependable representative of the total community population.
Three basic types of probability samples are considered below: the
single random sample, the stratified random sample, and the cluster sample.
12.2.1 Simple Random Sample
Each individual in the population has an equal chance of being
selected for inclusion in a. simple random sample. Take, for example, a
hypothetical community which contains 500 households. A simple random
sample could be drawn by writing the name of each household on a slip
of paper and then placing these 500 slips of paper in a hat. If a sample
12-2
-------
of 50 names were drawn from the hat at random, a 10% simple random sample
of households would have been drawn. By such a prodedure, each household
has an equal chance of being selected. Obviously, the characteristics of
the community are described more completely when more samples are drawn.
12.2.2 Stratified Random Sample
In a stratified random sample the population is divided into two or
more groups or strata. For example, a population might be divided into
income level or age level strata. If appropriate measurements were made,
a population could be divided into strata according to noise exposure
level. After this procedure is accomplished, a simple random sample is
taken from each stratum. These sub-samples are then joined to form the
total sample.
12.2.3 Cluster Sample
This type of sample is designed for relatively complex situations and
it is characterized by an initial sampling stage in which groupings or
clusters of the units to be sampled are selected by means of a simple
random or stratified random sampling procedure. If all the individuals
in a cluster are not to be included in the samples, then the ultimate
selection from within the cluster, is also made by a single or stratified
random sampling procedure. Cluster sampling is commonly referred to as
a multi-state sampling procedure.
Multi-stage sampling plans are commonly used in noise surveys. For
example, we might find that 30,000 people live within five miles of an
airport. Taking a simple random sample of a population this large would
be difficult and time consuming. It might be possible to divide this area
into 50 neighborhoods of approximately equal size. From these 50 neighbor-
hoods, 12 neighborhoods, or clusters could be selected at random. If noise
measurements were available, the 50 neighborhoods might be classified
according to noise exposure level—high, moderarte, or low. From each of
these three strata, four neighborhoods could be selected. In each case,
the ultimate samples might consist of 25 residents selected at random from
each of the 12 neighborhoods. The total sample would equal 300. For
large scale surveys cluster sampling is often more economic and efficient
than other sampling procedures.
12.3 Survey Design
In the course of designing a survey, there are several procedural
decisions that must be made. First, should the interview be structured
or unstructured? Second, should the questions comprising the interview
be of the fixed-alternative or open-ended variety? And third, should the
interview be direct or indirect?
12-3
-------
12.3.1 Structured vs Unstructured Interview
Structured interviews are frequently organized interviews in which
the questions to be asked, their wording, and order of presentation are
determined before hand. In an unstructured interview these matters,
within limits, are left to the discretion of the interviewer who works
only from a broad agenda.
The principal advantage of the unstructured interview is that it
permits the interviewer to pursue any aspect of the subject matter that
appears promising. The major disadvantage is that such freedom makes the
comparison of responses between different individuals very difficult.
Structured items on the other hand are more appropriate where there is
an interest in data quantification. Furthermore, some topics lend them-
selves better to structured formats while other topics do not. Most
noise surveys are'fairly structured, but often include optional questions
or areas of inquiry. Such options are very useful if the interviewer is
sophisticated and highly motivated.
12.3.2 Fixed-Alternative vs Open-Ended Questions
Fixed-alternative items consist of a question followed by a limited
set of possible responses to which the respondent is to select the one that
is most appropriate. The alternative responses might take the form of a
list of activities with which noise in the environment interferes or, the
individual might be asked to rate the noisiness of his neighborhood on a
seven-point scale, with 1= very noise and 7= very quiet.
Open-ended questions allow the individual total freedom in responding.
Responses to open-ended questions are difficult to quantify and analyze,
but they often result in providing the researcher with insights or
responses that had not previously been anticipated. Generally, it is
advisable to include both types of questions because some questions simply
cannot be answered by choosing an alternative.
12.3.3 Direct vs Indirect Interview
Should noise be acknowledged as the topic of concern? The direct
interview approach makes no attempt to disguise the purpose of the inter-
view, while the indirect approach attempts to prevent the respondent
from knowing that nosie is the primary purpose of the interview. The
indirect approach makes for a more lengthy of complex protocol, but doing
so may result in obtaining a more.realistic picture of the noise situation
in a particular community. It is possible that the noise problem might
appear more serious than it is if the survey deals only with noise. Survey
researchers have also argued that to avoid bias, interviewers should not
identify themselves as part of the government structure, but as part of
a university or general research organization (4,5). In light of the
aforementioned considerations, it might be prudent to begin the interview
in an indirect fashion in order to establish how noise ranks as a community
issue, and as the interview precedes to focus in a more direct fashion on
noise per se.
12-4
-------
As is probably obvious from the above discussion, most actual
interviews represent compromises on each of the above issues. The
actual structure and format of the interview is dependent to a large
extent on the nature of the problem area, and on availa.ble resources and
personnel. Community response to noise is usually studied via a structured
interview that includes a fairly high proportion of fixed-alternative
questions.
12.4 Model for the Design of Noise Surveys
A widely employed framework for the design of social noise surveys
includes the following four factors for consideration (5):
1) perception or awareness of noise
2) activities affected or interrupted by noise
3) annoyance or hostility resulting from interruption by noise
4) complaints resulting from interruption by noise.
The first factor pertains to the large individual differences that
exist in terms of perception and awareness of noise. Some people are
extremely sensitive to noise, while others are quite insensitive to it.
Thus, people who are exposed to the same noise will not all react to it
in a similar manner.
The second factor considered in this framework stems from the observa-
tion that the adverse effects of noise are closely related to the activities
which the noise interrupts. Therefore, in a noise survey, information
should be collected concerning the variety of activities intruded upon
by noise, and the extent or magnitude of this intrusion.
The third factor involves the extent to which people feel annoyed or
irritated by different types of noise. It has been found that certain
social, psychological, and situational variables play an important role
in mediating the annoyance and hostility responses of the individual
(Chapter 7 contains a list of some of these factors).
The fourth factor pertains to complaint activity. A survey of com-
plaint activity should include both the extent to which people desire to
complain, and the extent to which they actually do register such complaints.
Such information is typically included in noise surveys because there is
often administrative interest in predicting complaint activity. Research
has shown, however, that complaint rate represents a serious underestima-
tion of annoyance level (6). Complaint activity has been shown to be
related to a complex interaction of social and personal characteristics.
Most of the recent community noise surveys have, to some extent,
followed this general model. As will be discussed below, each of these
factors suggest a general category of questions that should be included
in a community noise questionnaire or interview protocol.
12-5
-------
12.5 Survey Content
In this subsection, the term interview will be used throughout to
denote both "interviews" and "questionnaires." Most large-scale community
noise surveys have employed interviews, but the recommendations contained
herein apply to both interviews and questionnaires.
The purpose of this section is to outline the major content areas that
should be included in a community noise survey. A complete survey should
contain items pertaining to the following four content areas: 1) descrip-
tion and assessment of the nosie environment, 2) activity disruption and
interference from noise, 3) psycho-social situational variables, and
4) personal-demographic background. Each of these areas are discussed in
detail.
12.5.1 Description and Assessment of the Noise Environment
Questions contained in this category should be directed at assessing
the respondents' perceptions of the noise environment in which they live.
This category corresponds to factor 1 in the survey model--perception or
awareness of noise.
The first question in this section might be indirect in nature and
simply inquire about sources of dissatisfaction in the person's environ-
ment. The purpose of this question is to assess how noise compares with
other problems in the environment. This permits a valid assessment of the
noise problem in that no prompting of the respondent has taken place.
Next, an overall "neighborhood" noise level rating should be obtained.
Similar overall ratings might be solicited for noise levels inside the
home, and for the city or town in general.
After the overall information has been obtained, the contribution
of various noise sources to this level should be assessed. Does the
noise come from aircraft, trucks, industry, barking dogs, etc. or some
combination of these? Some type of ranking procedure should be used
to assess the magnitude of the contribution of each of the sources to the
overall level. There are a variety of ways to accomplish this ranking,
but the general purpose of such a procedure is to determine the relative
contribution of the major noise sources. Information pertaining to the
times at which these noises are most obvious should also be obtained, and
an overall rating of the severity of "noise problems" is often also included
in the section.
Respondents might also be asked if they have ever complained to the
authorities about noise, or if they have ever thought of registering a
complaint. If they have thought of complaining but did not, it should be
determined what prevented them from doing so.
12-6
-------
12.5.2 Activity Disruption and Interference from Noise
It has been found that the extent to which noise is annoying depends
in part on the extent to which it disrupts ongoing activities. Items
in this section of the survey are related to factor 2 in the survey model.
Questions should be included that ask the respondent about the types of
activities that are disrupted by noise, and the degree of the disruption.
A list of such activities might included: TV/radio listening, conversation,
telephone use, relaxing outside, relaxing inside, listening to music,
sleeping, reading, eating, etc. Some -previous noise surveys have taken
the number of activities disturbed and calculated a total noise inter-
ference score. These scores have been used to represent an indirect
measure of annoyance (6). This section should also contain a direct
annoyance item. Such an item asks the person to state the overall extent
of his annoyance from noise in his living environment. Generally, there
is a good correlation between these indirect and direct annoyance measures.
It is often a good idea to include some questions of a more open-
ended variety in this section to probe the extent to which the respondent
has altered his daily activities to cope with the noise. The individual
may not feel that noise interferes with his sleep or TV watching, but
almost without awareness of the relationship of the noise to his behavior,
may report that he sleeps with the air conditioner on-all through the
year or that he always keeps the front windows closed. A family may have
moved the TV to the back of the house where it is quieter, or perhaps
they avoid backyard picnics because of the noise. These are effects
of noise that often go unnoticed.
12.5.3 Psycho-social and Situational Variables
Previous survey research has shown that there are a number of
intervening personal, social, and situational factors that appear to
affect responses to noise (2,5,7-9). For example, reactions to environ-
mental noise have been found to be more adverse if the noise is perceived
as being unnecessary, unpredictable or uncontrollable, or if the noise is
thought to represent a threat to personal health and safety. Similarly,
reactions are more adverse if the respondent feels that the authorities
or the propagators of the noise do not care about the problem, or if the
respondent is dissatisified with other aspects of the environment. Also,
self-ratings of noise sensitivity appear to correlate positively with
noise effects. That is, individuals who rate themselves as being sensitive
to noise tend to be more adversely affected by it (6).
12.5.4 Personal-demographic Background
Socio-economic background information is typically collected in the
course of any type of interview. These data fulfill several functions.
They provide information concerning the socio-economic makeup of the
sample, and the extent to which the sample is representative of the general
population. Also, patterns of response to items in the other parts of the
interview may depend on socio-economic variables such as age or income
level. Although this information is indispensible for the purposes of the
12-7
-------
interview, people are often reluctant to answer such questions. A
number of survey techniques have been developed which allow solicitation
of personal information while respecting the privacy of the respondent.
For example, sometimes broad categories of response are used to obtain
information on items such as income level. The respondent might be asked
to acknowledge only that his income is greater than $10,000 per year but
less tha $15,000 or greater that $5,000 per year but less than $10,000.
This approach avoides asking the individual to reveal an exact dollar
figure. Also, sometimes the respondent is asked to write in his own
answers instead of presenting them verbally to the interviewer. It
must be emphasized that this information should not be omitted from the
community noise survey solely on the grounds that it is sometimes difficult
to obtain.
Information concerning the age, sex, and national origin of the
respondent should be collected. An index of socioeconomic status should
be obtained from questions dealing with the respondents educational level,
income level, and occupational classification. The interviewer's personal
noise exposure history should also be taken. This entails information
concerning both the person's previous occupational and non-occupational
noise.exposures.
Since most interviews are conducted in the home and thus deal
primarily with residential exposures, some information concerning the
person's residential environment should be gathered. It should be
determined whether the property is owned or rented, the type of housing
(apartment, single family, - detached, etc.), the length of residence,
the desire to relocate, age of building, number of rooms, etc. Factors
such as these are often related to annoyance and complaint activity.
12-8
-------
REFERENCES
1. "Effects of Noise on People," U.S. Environmental Protection Agency,
December, 1971 (National Technical Institute Document No. 300.7).
2. McKennell, A.C., Noise Complaints and Community Action, In J.D.
Chalupnik (Ed.), Transportation Noises: A Symposium on Acceptability
Criteria, Seattle: University of Washington Press, 1970.
3. Selltiz, C., Jahoda, M., Deutsch, M. and Cook S.W. Research Methods
in Social Relations (revised edition) Holt, Rinehart and Winston,
New York, 1959.
4. Bragdon, C.R., Noise Pollution, University of Pennsylvania Press,
Philadelphia, PA. 1971.
5. Borsky, P.N., The Use of Social Surveys for Measuring Community
Response to Noise Environments, In J.D. Chalupnik (Ed.) Transporta-
tion Noises: A Symposium on Acceptability Criteria, University
of Washington Press, Seattle, 1970.
6. Tracer, "Community Reaction to Airport Noise, NASA Report CR-1761, 1971
7. Graeven, D.B., Necessity, Control and Predictability of Noise as
Determinants of Noise Annoyance, Journal of Social Psychology, 95,
85-90, 1975.
8. Graeven, D.B., The Effects of Airplane Noise on Health: An Examina-
tion of Three Hypotheses, Journal of Health and Social Behavior, 15,
336-343, 1974.
9. Humphrey, C.R., and Krout, J.A., Traffic and the Suburban Highway
Neighbor, Traffic Quarterly, 593-613, October, 1975.
12-9
-------
Chapter .13
SOUND MEASUREMENT LABORATORY AND FIELD EXERCISE
The hands-on sound measurement laboratory and field exercise consists
of four parts. Initially, there will be a one hour review of sound measure-
ment instruments and procedures. This review will be followed by a three
hour laboratory exercise that covers the function and use of sound level
meters and analyzers. Recorded sounds will be available for these exercises.
Another three hour period will then be spent at pre-selected locations in
the community taking noise measurement data. After these field measurement
exercises have been completed, a summary discussion period will be held.
13.1 Sound Level Meter
13.1.1 Instruction Manual
. Use the instruction manual for the sound level meter to determine:
1) Overall accuracy -- Type 1 or 2
2) Range of sound levels and frequencies that can be measured
3) Recommended battery type and how to check and to change
batteries
4) Recommended microphone orientation with respect to the
direction of arrival of the sound
5) Recommended procedure for connecting external equipment
such as tape recorders, analyzers, or headphones.
Can these devices be connected to the SLM output without affecting
the accuracy of the meter indication?
13.1.2 Operating Controls
Handle sound level meter for familiarization with the following
controls and functions:
1) ON-OFF switch
2) Battery check switch
3) Battery compartment -- Are the batteries properly installed?
4) Sound level dB range switch -- Are the dB ranges indicated
on the knob or are they shown on the meter face? Under-
stand how to read the meter after the dB range has been
selected.
5) Weighting switch -- Does the SLM have A, B, and C weightings?
(Certain special meters have A-weighting only)
6) Fast-slow meter response switch
7) Calibration adjustment screw
One sound level meter should be provided for each pair of students.
-------
13.1.3 Field Calibration
Always use a field calibrator that is specified by the SLM manufacturer.
Field calibrations should be made prior to and after each day's use of a
SLM. Also, if the SLM accuracy is suspect during the day (if it is
dropped) other checks should be made. Field calibrators are intended
primarily for these short-term checks and most are quite stable and accu-
rate for this purpose. However, the calibrator can become defective so
this possibility should be kept in mind. If adjustments are found to be
necessary to make a SLM reading correspond to that of the calibrator,
it is highly probable that the calibrator is correct. However, if the
adjustment is significant (greater than 1.0 dB), a note should be made
of this adjustment and at some convenient time in the future the calibra-
tor should be checked. The calibrator can be checked by comparing its
output with that of another calibrator on a SLM, or it can be sent to the
manufacturer or a competent laboratory for evaluation. In any case, the
calibrator accuracy should be checked at least once each year.
1) Turn the sound level meter ON and check the battery. If
the battery check is OK, set the sound level meter controls
to:
a) C or Flat frequency weighting
b) Fast meter response
c) dB range to read the sound pressure level to be
produced by the calibrator. (For instance, if
the calibrator produces 114 dB, set the dB range
so that the meter can read 110 to 120 dB. On
most basic meters, this is called the "110 dB
range").
2) Turn the calibrator ON and check its battery as described
in the instruction manual for the calibrator. If the
battery check is OK, set the calibrator to 1000 Hz and
slowly fit the calibrator over the microphone on the sound
level meter^. (Some calibrators have a momentary push
button which must be held on to operate). Be sure the
calibrator is firmly seated on the microphone. (Some
calibrators seal around the microphone with a rubber "0"
ring and require extra effort to slide the microphone past
this "0" ring to seat firmly in the microphone cavity).
The sound level meter should read the level specified
for the calibrator within the specified accuracy,
typically ±0.5 dB. If the reading is outside this range,
adjust the SLM calibration screw to make the SLM read
correctly. Turn the calibrator off and gently remove it
from the sound level meter. The sound level meter is now
field calibrated and ready for use.
p
Some calibrators provide frequencies in addition to 1000 Hz. These
alternate frequencies provide a means for checking the instrument
performance more thoroughly and they can be used to check the response
of the A-weighted network by comparing the A-weighted reading with the
response curves published in the instruction manual (see also Figure 11.1),
13-2
-------
3) Final checks and Adjustments
a) Battery -- if the battery check indicates bad or weak
batteries in either the SLM or the calibrator, install
fresh batteries. Many sound level meters use more
than one battery. Replace all batteries even if only
one appears to be bad. If correct operation is not
restored, check battery connectors to be sure they
are making firm, positive contact. Failure to achieve
a correct battery indication means an internal defect
which should be referred to the instrument manufacturer
or a competent repair facility.
b) Calibration -- a low or high reading of the calibrator
that cannot be corrected by the SLM adjustment screw
may mean a damaged microphone or defective SLM or cal-
ibrator. If the SLM response is correct at 1000 Hz
but is in error at other frequencies, the most likely
cause is a damaged microphone. In any case, the SLM,
microphone and calibrator should be referred to the
manufacturer or a competent facility for repair.
c) Fast-Slow Response -- the dynamic characteristics of
the indicating meter can be checked by talking into
the microphone with the dB range set to 70 dB and the
meter response set to FAST. The needle should jump
and fall back with each word in a sentence. With the
meter response set to SLOW, the needle should not drop
noticeably between words but should follow the inflec-
tion of a spoken sentence. Although this test does
not give a quantitative check of the FAST-SLOW time
constants, it will indicate whether the switch is
making contact and is, indeed, changing the meter-
response time constant.
13.2 Analyzers
The basic measuremet needed for an octave- or one-third octave-band
analysis may be outlined as follows:
1) Obtain a sound level measurement with the weighting control
set at "Linear" or "Flat" response. Record this reading on
the survey data sheet.
2) Switch to A-weighting and record the reading also.
3) Next, switch in the analyzer and record the level read in
each of the frequency bands selected. Be particularly
careful to follow the instrument manufacturer's instruc-
tions to avoid errors that may result from overloading in
some instruments. A suggested data form for recording
octave-band data is discussed in Chapter 11. Note: On
certain instruments, the A-weighting network must be
switched out separately when using the analyzer. When
making an analysis, the signal fed to the analyzer should
not be modified by any weighting network. That is, the
"Linear" weighting should be used. If "Linear" is not
available, "C" weighting can be used but should be noted
13-3
-------
on the data sheet. On most instruments this is done
automatically when the instrument is switched to the
analyzer bands if the procedure outlined in the instruc-
tion manual is closely followed.
13.3 Record Keeping
A suggested form for noise level surveys is shown in Figure 13.1. A
blank copy of this form, the Community Noise Survey Data Sheet, is pro-
vided in Appendix A to this chapter. Copies of these blank forms (or
the forms, if different, that will be used) will be supplied to each
participant. During this laboratory period the use of the forms will be
explained in preparation for the field exercise.
13.4 Sound Measurement Laboratory
13.4.1 Sound Measurement Training Tape
A collection of special sounds will be supplied on a monaural cassette
tape recording for realistic laboratory exercises. The following equipment
is recommended for reproducing these sounds:
1) Monaural cassette player
2) Amplifier-speaker system with minimum of 10 watts audio
power delivered to the speaker
3) Necessary connecting cables
Do not attempt to use the loudspeaker built into the cassette player.
Although reproduction of the original sound level is not necessary, the
audio power available in portable, battery operated cassette players is
inadequate to reproduce these sounds for laboratory instruction.
A description of the taped materials is listed in Table 13.1. The
musical selection at the beginning of side 1 is provided so that a satis-
factory sound level can be set. The following procedure is suggested:
1) Adjust the system volume controls to produce an average
music level somewhere between 80 and 85 dB(C) at 3 to
4.5 meters (10 to 15 feet) from the loudspeaker. This
should be achieved without noticeable distortion of the
music. The controls should remain at this setting for the
remainder of the recorded material.
2) In the event that your amplifier-speaker system will not
operate at this level without objectionable distortion,
reduce the level until a satisfactory, clear sound is
achieved.
These demonstration tape selections are intended to illustrate the
nature of some sounds that may be encountered in a community. The
selections are arranged approximately in order of increasing difficulty
of measurement.
13-4
-------
Figure 13.1
COMMUNITY NOISE SURVEY DATA SHEET
Day of week 'a, Month ^i/ Day tf Year
/ (^-ar^r _ i _ f)e
/ P -I—
Measurements made by _ y- / f 0 y I
Weather:
Temperature^5~ F
Humidity
%
Cold
Dry
Cool
Humid //
Moderate
' Rain*-
Hot
Snow*
Wind mph. Calm Breezy ^ Gusty Strong*
Sound sources in area p iy '6~f> tes^e^ a~t~ Ct?h&1~ rvt-'Wb
Sound level meter Type Q- /f 'l£'6£~8 Serial No. 0$ I
Calibrator Type Q ft J $(*'}--• 4 Serial No.
Battery check Time: (?$tT'hrs J3CQ hrs X^jV hrs hrs
Sound level meter
Calibrator ^/T Q ff
Calibration of Sound level meter
lOOOHz /dB HlfQdT /dB dB
SOOHz //V;^> dB //Vr^l dB J/ dB dB
250Hz /dB /y> dB dB dB
125Hz ;dB /dBdB dB
ZOOOH-s /V; 2 dB dB dB _ _ dB
* Measurements not recommended in unusual weather conditions.
13-5
-------
Figure 13.1 (cont)
COMMUNITY NOISE SURVEY DATA SHEET
Sketch of area.
Day of week \V& d >, e * d
-------
Figure 13.1 (cont)
COMMUNITY NOISE SURVEY DATA SHEET
Sound pressure level measurements
Day of week VV^cl / Month plf?\/ Day $& Year /
Location '' (?7 L^ar^y- /l^
A
2
A
S h
z
A
3
7/
A
13-7
-------
Table 13.1
NOISE TRAINING TAPE 7.5 ips 15 minutes each side
Side Subject Time VU
Selection
1 1 Music to check system 2:22 -3
+ 1 pk
Blank :10
2 Purple noise 8:00 -12
Blank :10
3 Purple noise with
250 HZ pure tone 4:00 -8
2 1 Traffic sounds at
busy intersection 4:00
tflank :05
2 Garbage truck
two dumps 5:15
Blank ' :05
3 Lawnmower 1:30
Blank :05
4 Children at play 3:30
Notes:
Purple noise is filtered from Pink Noise with Lo pass filter
set at 500 Hz and Hi pass filter set at 2500 Hz.
Garbage truck sequence:
Dump first container
Back up
Compact
Dump second container
Flip lid closed on container
Back up
L/eave
Lawnmower approaches edge of lot next door. Recorded from
bedroom window.
Children are playing approximately 100 feet from microphone.
13-8
-------
13.4.2 Use of Recorded Materials
After the system volume controls have been adjusted by using the
musical selection, a selected sound is provided that can be repeated as
often as necessary for initial familiarization with the operation of
sound measuring instruments. This sound spectrum has been chosen because
it is easy to measure and because it affords reasonable voice communication
during the measurement exercises. This spectrum is a "pink" noise3 that
is modified by reducing the sound levels in the speech frequencies between
500 and 2500 Hz. This recording is particularly useful to demonstrate the
differences in A-weighted and C-weighted sound pressure levels.
The variation in sound level readings at different locations within
the classroom will illustrate the way sound propagates through the room.
(The propagation loss should be observed to be something less than 6 dB
per doubling of distance from the loudspeaker because of reflections from
the walls of.the room).
The last 4 minutes of side 1 of the tape contains the same sound
spectrum (level and frequency distribution) but with an added 250 Hz pure
tone (single frequency). Note that the sound level reading increases due
to the added energy of the pure tone. The level may also vary due to
standing waves set up in the room by reflections from the walls and other
surfaces. The variations in level due to standing waves may be observed
on the SLM when it is moved short distances within the room. This kind
of sound is often produced by a rotating machine or a resonant device
such as an ultrasonic cleaner.
Sound level meters and sound analyzers can be used to measure the
material on the demonstration tape. The notch in the first sound spectrum
presented after the musical selection on side 1 of the tape will produce
a difference between A- and C-weighted sound level meter readings but the
shape of the notch cannot be described. More information regarding the
shape of the notch will be provided by the octave bands centered at 250,
500, 1000, or 2000 Hz. However, it will be obvious that the one-third
octave analysis will provide much more complete information on the notch
shape from the one-third octave bands between 315 to 3150 Hz.
Side 2 of the demonstration tape contains some frequently encountered
community sounds. The first is the sound of vehicles at a major signal-
controlled intersection during the early morning rush period. The
second selection is the sound of a garbage truck dumping two containers.
The third selection is the sound of a lawnmower as the mower approaches
the observer. The final selection is the sound of children at play in a
school yard.
Pink noise is a common term used to describe a sound "having equal energy
in each octave band.
13-9
-------
The selections on side 2 demonstrate the problems of measurement of
time-varying sounds. The effects of FAST and SLOW meter responses and the
difference between A- and C-weightings should be especially noted. It is
instructive to note the levels of these sounds above the ambient and, in
the case of the garbage truck, to note the very high peak levels that occur
with the slamming of the container lids. The demonstration tape will be
rewound and the sounds repeated as necessary during the training periods.
However, in a real situation, the sound cannot be repeated as it can with
the tape recorded signals. Time will be allowed during this training period
to answer questions regarding the operation of the sound level meter and
to discuss problems of measuring real, fluctuating sounds in compliance
with the local noise ordinances.
13.5 Community Sound Measurement
The afternoon session of the sound measurement laboratory will be
devoted to measurements at preselected locations within the local community.
Trips will be planned to measurement sites such as construction sites,
hospital zones, playground areas or congested downtown areas. Measurements
will be made according to procedures described in the local noise ordinance
whenever possible. At least one statistical time sampling should be made
using the procedures and data form suggested in Chapter 11. Students
will be scheduled for a question and answer session after the field exercise.
13-10
-------
APPENDIX A TO CHAPTER 13
COMMUNITY NOISE SURVEY DATA SHEET
13-11
-------
COMMUNITY NOISE SURVEY DATA SHEET
Day of week
Month
Day
Year
Location
Measurements made by
Weather:
o
Temperature F Cold
Humidity % Dry
Cool
Moderate
Hot
Humid
Rain*
Snow*
Wind
mph. Calm
Breezy Gusty
Strong*
Sound sources in area
Sound level meter Type
Serial No.
Calibrator
Type
Serial No.
Battery check Time: "j hrs
Sound level meter
hrs
hrs
hrs
Calibrator
Calibration of Sound level meter
lOOOHz
SOOHz
250Hz
125Hz
ZOOOIts
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
dB
* Measurements not recommended in unusual weather conditions.
13-12
-------
COMMUNITY NOISE SURVEY DATA SHEET
Sketch of area.
Day of week Month Day _Year
Location
Show buildings, trees, bushes, parked vehicles, distances to sound
sources. Mark location of microphone with(o). Show microphone height.
13-13
-------
COMMUNITY NOISE SURVEY DATA SHEET
Sound pressure level measurements
Day of week Month Day Year
Location
/
cb
13-14
-------
APPENDIX B TO CHAPTER 13
MANUAL SAMPLING DATA SHEET
13-15
-------
OJ
I
SOUND LEVEL METER TYPE.
STARTING TIME.
SAMPLING INTERVAL.
SERIAL
PRIMARY NOISE SOURCE
SECONDARY NOISE SOURCE.
COMMENTS
TOTAL OBSERVATION TIME.
&
I 2 3
19
i 8
' 17
15
;4
1-3
12
n
0
i <9
! -8
7
I '6
i 5
i 4
! .'3
i 2
1 1 1
! 0
9
i 8
1 7
>5
A
3
1 2
iO
;9
8
|7
16
;5
'4
3
i2
! |
o
•
id
<
1 /
qf
4C
)(
5-
2
o
2
m
fe
co
s
m
>
NUMBER OF OCCURANCES
-------
APPENDIX C TO CHAPTER 13
NOISE SURVEY DATA SHEET
13-17
-------
EAL
ENVIRONMENTAL ACOUSTICS LABORATORY
The Pennsylvania State University
110 M°°re BuildinS
University Park, PA 16802
Phone (814) 865-5414
Travel, Accommodations, and Expense Reimbursement
Community Noise Training Workshop
Penn State University
The University Park Campus of Penn State is located approximately in the
geographical center of the State within the Borough of State College. Travel
to/from Penn State is discussed more fully in the attached flyer. Recently air-
line service has undergone substantial changes so that now:
1) Allegheny Airlines comes into the University Park Airport
(5 miles away) as well as the Mid-State Airport with service
to and from Pittsburgh and Washington, D. C. Telephone
(814) 238-8414.
2) Trans-Penn Airlines provides service to and from University
Park with service to and from Pittsburgh and Baltimore.
(814) 237-3604.
3) Air-Atlantic Airlines provides service to and from University
Park Airport with service to and from Philadelphia (extension
of service to New York City has been proposed for September
1978). (814) 364-1477.
A limited number of rooms has been set aside for workshop participants at
the Nittany Lion Inn for the nights of October 2, 3, and 4. The Inn is located
adjacent to the Keller Conference Center on Campus, where the Workshop will be
held. Please confirm your reservation as soon as possible by contacting:
Nittany Lion Inn, North Atherton Street, State College, PA 16801 (814) 237-7671
(When doing this please mention that you are with the EPA Community Noise
Workshop group.)
Participants who are not Federal employees may expect to receive full
reasonable reimbursement for travel, lodging, and subsistence expenses from
Penn State. Travel expenses will be reimbursed directly and completely for air
and land transportation fares at the rate for normal tourist (coach) travel.
If traveling by private automobile, you will receive $.15 per mile for the
listed distance from point of origin to University Park and return. Expenses
for food will be allowed for amounts up to $15.00 per day. Payment will be
made subsequent to the completion of travel and after submission of a travel
expense accounting. Receipts for travel and accommodations must be submitted
along with your expense account. If desired, pre-paid round-trip airline
tickets will be made available at your point of departure. Please contact
either Dr. Paul L. Michael or Roger L. Kerlin at the Environmental Acoustics
Laboratory to discuss your particular requirements - telephone (814) 865-5414.
-------
NOISE SURVEY DATA SHEET
DATE
LOCATION
^
OCTAVE BAND
(Center Freq. )
Over all -Linear
A-Frequency
Weighting
31 Hz
62 Hz
o^ 125 Hz
oo 250 Hz
500 Hz
1000 Hz
2000 Hz
4000 Hz
8000 Hz
Taken By:
DECIBELS
Time •
Remarks:
DECIBELS
Time-
Remarks:
-
DECIBELS
Time-
Remarks:
DECIBELS
Time-
Remarks:
DECIBELS
Time-
Remarks:
DECIBELS
Time:
Remarks:
Sound Measuring
Equipment:
Typp
Mr,^0l #
S~T-;*i #
lype
K/fr,Hpl #
Serial #
OCTAVE BAND
(Center Freq. )
Over all -Linear
A-Frequency
Weighting
31 Hz
62 Hz
125 Hz
250 Hz
500 Hz
1000 Hz
2000 Hz
4000 Hz
8000 Hz
FIELD
CALIBRATION
Cal. Type
TIT*
Freq. , Hz dB
!?<;
?<;n
snn
innn .
?nnn
-------
APPENDIX A
A DISCUSSION OF STRUCTURE-BORNE VIBRATION
A-l
-------
APPENDIX A
A DISCUSSION OF STRUCTURE-BORNE VIBRATION
In the specific prohibited acts section of the document "Model
Community Noise Control Ordinance" (1), there is a chance that proposes
prohibiting the creation of vibration which is above the perception
threshold of an individual. This vibrational motion would be one that
is ground - or structure-borne from the location of some source to
another site (adjacent property). This provision, as well as each of
the other ones in the "Model Ordinance", is proposed to be appropriate
only., as may be found suitable to local needs and conditions.
Structure-borne vibration may have physiological and psychological
effects on the individuals who are exposed to it. These effects depend
on many complicated and interrelated factors, such as the magnitude and
frequency of the vibration; its locational site, area, and direction of
application; and individual variations in susceptability. An individual's
susceptibility to vibrational effects is determined in part by their
physical state, age, muscle tone, size and weight, etc. Further, the
effects of vibration may be heightened or diminished by the physical or
mental state of the exposed individual, their activity, or the presence
of additional environmental stressors such as concurrent exposure to
noise or heat. The vibration frequency, which may range from 0.1 to
1,000,000 Hz, largely determines the kinds of effects experienced (2,3).
Adverse effects may range from motion sickness (kinetosis), which occurs
primarily from exposure to very low vibration between 0.1 and 1.0 Hz, to
local tissue heating and possible cell damage which can result from
exposure to vibrational frequencies in the ultrasonic range above 20,000 Hz.
For purposes of this discussion, only structure-borne vibration that
commonly has levels above the perception threshold for humans is being
considered. Thus, consideration of those vibrations with frequencies
above 1000 Hz will be eliminated 1) because humans are relatively insen-
sitive to these high frequencies and 2) because high frequency vibrations
are attenuated very rapidly as they propagate away from the source. An
International Standard, ISO 2631, "Guide for the Evaluation of Human
Exposure to Whole-Body Vibration," sets forth many of the particulars
that define and specify the scope of interest for documenting and describ-
ing a vibration environment (4). According to the vibration perception
threshold criteria, outlined in this discussion, the descriptive para-
meters of vibration exposure are specified in term of vibration frequency,
acceleration magnitude, and the way that the human body is vibrated.
A-2
-------
CHARACTERIZATION OF VIBRATION
Temporal Characters Vibration perception criteria normally specify
vibration levels that correspond to threshold levels of average or normal
individuals in good health. These vibration levels may be either periodic
or, random in time with a distributed frequency spectrum. Vibration per-
ception criteria do not usually specify durations of exposure to vibration
that might lead to various biological and/or performance effects over
different times of total exposure.
Spatial Character: Vibration is a vector quantity that may be
either angular or rectilinear. Rectilinear vibration specified in any
one of the three orthogonal axes with respect to the human body will be
used for the purposes of this discussion.
Magnitude: The quantity used to measure the "amount" or magnitude
of vibration may refer to the displacement, velocity, acceleration, or
jerk of the vibration. The quantity used throughout this discussion
refers to the acceleration magnitude of the vibration expressed as a root-
mean square value in nondimensional units of g's where 1 g=980.665 cm/sec^
is the value of the standard acceleration due to gravity at the earth's
surface. (Acceleration magnitude is also commonly found expressed: in
units of meters per second squared, m/s?; as a level in dB referenced to
some standard value; as peak values; etc.)
Spectral Character: Vibration may occur with many different
frequency compositions. Discrete-frequency vibration may consist of a
single frequency component or multiple components; distributed-frequency
vibration may be composed of a single narrow-band of frequencies or a
combination of more than one such narrow-band of frequencies into a
broad-band distributed vibration.
Transmission: The transmission of vibrational energy from a source
through the ground and/or structural connections to a reception location
may involve many changes in the characterisitcs of the vibration along the
transmission path. Various properties of the transmission medium or media,
and reception structures can be expected to change the magnitude, direc-
tion, and frequency spectrum, of vibration along its path of propagation.
Of particular note will be relatively large-magnitude vibrations that
may be induced at particular frequencies that correspond to resonant
frequencies of receiving structures. Consequently, the description or
measurement of vibraiton must include a detailed description of the loca-
tions selected for measurements.
VIBRATION PERCEPTION
Both physical and subjective methods of vibration measurement are
acceptable, however, the physical measurement is the preferred method.
Subjective awareness to vibration will depend upon 1) the frequency and
A-3
-------
the magnitude of the stimulus, 2) the individual's response characteristics,
.and 3) the environmental conditions. Vibration perception threshold may
be defined as the minimum vibrational acceleration that is necessary to
cause a normal person to have a touch (in contact) or visual sensation of
vibration. In some cases an individual may be unaware of levels of
vibration higher than those of his threshold of perception because of
distracting conditions. However, Once attention is directed to the vibra-
tion, awareness may be anticipated.
At frequencies below 1 Hz vibration is sensed primarily by means of
the vestibular organs along with somatic receptors in the areas of
application of the vibration to the body. Above 1 Hz where body resonances
and phase shifts in the transmission of vibration occur, the vestibular
sensation is augmented by the stimulation of mechano-receptors throughout
the body, including those in the muscles, tendons and joints as well as
in the skin and in the viscera, and by visual cues. The sensations pro-
duced by whole-body vibration at frequencies less than 50 Hz vary with
frequency and are related to body resonance. Beginning at about 15 Hz,
the skin may be considered the chief sensing mechanism for vibration
detection. The threshold of cutaneous perception, tested at a finger-tip
is lowest in the region of 200-300 Hz; the sensitivity depends on the
area, site and pressure of application and is related to muscle tone.
Threshold criteria for rectilinear vibration perception exists in
the literature. One set (5), is based upon a simple average of results
of laboratory experiments involving human perception of single frequency
whole-body vibration in standing, sitting, and lying positions. This
data, which covers the frequency range of vibration from 1 to 50 Hz,
is used in this discussion as the whole-body threshold perception level
for any body orientation (standing, sitting, etc.). Consequently, it
may be necessary to measure vibrations in several directions and to deter-
mine the vector sum of all components before comparing the exposure level
with the perception criteria.
In the frequency range from 50 to 1000 Hz, vibration perception
criteria are usually expressed in terms of fingertip sensation levels (6).
Vibrations with frequencies higher than 1000 Hz are rarely a problem
because these vibrations are rapidly attenuated with distance from the
source, and because the human perception sensitivity falls off rapidly
with increasing vibration frequency. The widely accepted vibration percep-
tion criteria for the frequency range from 1 to 1000 Hz are presented in
Figure A-l.
MEASUREMENT METHODOLOGY
Physical measurements or subjective detection of vibration perception
threshold levels may be indicated for the purposes of enforcement of
ordinance criteria on exposure to vibration.
A-4
-------
10
1.0
10"
to o>
S-
<1) (/)
O) C£.
O
O
10"
10"
Figure A-l. Threshold of Vibration Perception
Criteria. Frequency dependence of the root-
mean-square acceleration magnitude for vi-
bration in units of g = 980.655 cm/sec2.
The solid-line curve represents the depen-
dence of average values for whole-body
vibration at single frequencies taken
from the analysis by Goldman (see his
Table 2)5, and the dashed-line curve
represents the dependence of threshold
at the fingertip taken from the work of
von Be'ke'sy (Abb. 20, page 331 )6.
50
100
500 1000
Frequency, Hz
A-5
-------
Subjective Detection of Vibration: Subjective awareness of vibra-
tion should be easily determined when levels of vibration are significantly
above perception threshold. In these instances, most individuals includ-
ing those responsible for enforcement of vibration control would be able
to confirm the existence of prohibitive levels whenever any perceived
level is prohibited.
When vibration is at a level above and yet close to that for
perception threshold, it may require more attention to confirm its
presence. The enforcement specialist may be required to assume a parti-
cular orientation or location of the body so as to become aware of the
vibration. Because the presence of additional persons may reduce the
vibration magnitude, care should be taken to duplicate conditions described
by those persons initiating a complaint. Depending on the particular
circumstances, vibration may be detected through various means such as:
whole-body Vibration input to the supporting surfaces of the body (standing,
Seated, or lying down); cutaneous perception as With the hands on a table,
shelf, etc.; or visual observation of vibrating objects.
It should be a matter of practical consideration that only normal
activities be included among those circumstances of vibration exposure
being evaluated for the presence of vibration levels above perception
threshold. Thus, for example, vibration of a floor joist that is detectable
only through a sense of direct touch with the fingertips would not
constitute a condition producing "normal" awareness to the vibration.
However, if this same vibration is transmitted from joist to floor surface
and then detectably to a person supported by the floor, the vibration
may be classified as a prohibitive level.
Measurement of Vibration: The root-mean-square (rms) acceleration
levels measured in one-third-octave bandwidths with center frequencies
beginning at 1 Hz and ending at 800 Hz, which includes the frequency
range from 0.9 Hz to 900 Hz are normally used for the physical measure-
ments of vibration. The requisite system of equipment for measuring vibra-
tion generally consists of the following parts: a vibration pick-up
(randucer), a suitable amplifying and singal conditioning device, and an
indicator of output level. More specifically, this system consist of
an accelerometer, an amplifier, and a rms-rectifying indicator with
provisions of one-third-octave-band analysis. The system should have
sensitivity to accelerations as low as 0.001 g at frequencies between
1 and 10 Hz and as large as 1 g at frequenices above 200-300 Hz. Instru-
ments with features that meet such requirements are commercially available.
In addition, vibration calibrator are available that may be used to cali-
brate the system by providing a known vibration (acceleration) input.
Instructions for the use of accelerometers as set forth in the
literature and by manufacturers should be closely followed (7-10).
Accelerometers can be used to measure vibration over wide frequency and
dynamic ranges, but particular attention must be paid to the location and
placement or mounting of the accelerometer. If possible, the unit shoutd
be mounted on a rigid and smooth surface that experiences the vibration
that is to be measured. The axis of the unit will designate the direction
of the component of vibration being measured, and consequently, this
information should be recorded. Triaxial accelerometers are available
that combine three separate units oriented in mutually orthogonal directions
A-6
-------
such that the resultant acceleration vector may be fully determinded -
the magnitudes of orthogonal components. However, a single unit may be
utilized to obtain this same information either by taking data for three
mutually orthogonal' directions or by measuring the acceleration magnitude
along the major axis of vibration.
The accelerometer may be mounted by any of several methods. Generally,
a threaded hole or a bolt is provided in the base of the accelerometer
that permits mounting the unit directly to a surface, to a special adaptor
that may then be cemented to a surface, or to a magnetic base that will
attach readily and securely to surfaces of ferro-magnetic materials. The
accelerometer may also be mounted by means of double-sided tapes, cements
(for permanent type installations), or greases. In all cases, the mating
surfaces should be smooth and free of dirt. A light coating of oil or
grease is recommended between metallic mating surfaces that will be in
direct contact.
Measurements are to be performed at locations that correspond to the
point or points of complaint and should be carried out upon that surface
which is effecting the input of vibration to the complainant. Examples
are flat surfaces of floors, desk or table tops, chair seats, etc. whereon
the accelerometer is mounted directly. The measurement system of
accelerometer and instrumentation should be calibrated prior to and after-
measurements and at any time during measurements whenever the operation
of the system may become suspect, for example, whenever the transducer
suffers a severe shock such as from an accidental fall. Acceleration
magnitude (rms) should be measured in one-third-octave bandwidths and com-
pared with those levels that correspond to vibration perception threshold
at the center frequencies of the one-third-octave bandwidths (see Table
A-l). The axis of the measurement should be recorded. In certain cases
where this axis does not correspond to the major axis of the vibration
stimulus, each of three orthogonal components should be measured and
evaluated with regard to the perception criteria (Table A-l) along with
the magnitude of the vector resultant. (The resultant is equal to the
square root of the sum of the squares of the orthogonal components.)
Whenever a measured level for any one-third-octave bandwidth exceeds a
corresponding level of threshold of perception shown in Figure A-l and in
Table A-l, the vibration level may be out of compliance with ordinance
requirements. It is appreciated that this method for the comparison of
measured one-third-octave bandwidth levels with criteria that are based
.upon single frequency exposure data is an approximation and that circum-
stances may occur where such an application is inappropriate.
A-7
-------
Table A-I Vibration Threshold of Perception Criteria.
Values are for the root-mean-square acceleration
in units of g = 980.665 cm/sec^ for the fre-
quencies at the center of the one-third-octave
bands beginning 1 Hz and ending 1000 Hz. Values
have been determined from the curves of Figure A-I.
Center-Frequency of
One-Third-Octave Band,
Hz
Accerleration (rms)
Foir Threshold of Perception
in g = 980.665 cm/sec2
Whole-Body
Finger-Tip
1
1.25
1.6
2
2.5
4*
5
6.3
8
10
12.5
16
20
25
31.5
40
50
63
80
100
125
160
200
250
315
400
500
630
800
1000
1.
3.
2.
2.
9
t- •
1.
1.
2.
2.
3.
4.
6.
7.
1.
1.
1.
1.
8
F
2
7
3
i
j_
9
8
0
6
5
4
0
7
0
2
4
4
x 10"
0028)_
x 10"
x 10"
x 10"
x i n~
x
x
x
x
x
x
x
x
x
x
x
x
_ _ _
_ _ _
-i_vy
10"
10"
10"
10"
10"
10"
10"
10"
10"
10"
10"
10"
_ _
—
—
_ _
—
--
--
--
—
—
3
3
3
3
3
3
Q
3
3-
~
9
Z
2
9
Z
0
^_
8.
1.
1.
2.
3.
5.
8.
9.
9.
8.
6.
5.
4.
4.
3.
3.
3.
4.
8.
1.
4.
1.
3
2
9
7
9
9
3
2
0
0
9
8
9
2
6
4
6
9
8
8
6
6
—
—
x
x
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
1.
%
--
--
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
10
0
8
0
- o
-3
o
- J
Q
o
o
- j
o
- J
f\
9
— Z
•_1
J_
A-8
-------
REFERENCES
1. "Model Community Noise Control Ordinance," U.S. Environmetal Pro-
tection Agency, Public Information Center (PM215), Washington,
D.C. 20460, EPA Document No. 550/9-76-003, September 1975.
2. Guignard, J. C., Chapter 28, "Introduction" and Chapter 29, "Vibration,"
in A Textbook of Aviation.Physiology, edited by J.A. Gillies, Pergamon
Press, New York, pp. 807-894, 1965.
3. Goldman, D.E. and H.E. von Gierke, Chapter 44, "Effects of Shock and
Vibration on Man," in Shock and Vibration Handbook, Vol. 3, edited
by C. M. Harris and C.E. Crede, McGraw-Hill Book Company, New York,
pp 44-1 to 44-51, 1961.
4. ISO Standard, Publication ISO 2631-1974, Guide for the Evaluation of
Human Exposure to Whole-Body Vibration, 1974.
5. Goldman, D.E., "A Review of Subjective Responses to Vibratory Motion
of the Human Body in the Frequency Range 1 to 70 Cycles per Second,"
Report No. 1, Project NM 004 001, Naval Medical Research Institute,
National Naval Medical Center, Bethesda, MD, 16 March 1948.
6. von Bekesy, G., "Uber die Vibration sempfindung," Akust. Z. 4_, 316-334
(1939).
7. B&K Instruments, Inc., 5111 West 164th Street, Cleveland, OH 44142,
Mechanical Vibration and Shock Measurements, by J.T. Broch, 311 pp.,
Rev. Edition, May 1972.
8. Endevco Corporation, Pasadena, CA, Piezoelectric Accelerometer Manual-.
by D. Pennington, 119 pp., 1965.
9. Gen Rad, 300 Baker Avenue, Concord, MA 01742, Handbook of Noise
Measurement, 7th Edition, by A.P.G. Peterson and E.E. Grose, Jr.,
322 pp., 1972.
10. Wilcoxon Research, P.O. Box 5798, Bethesda, MD 20014, Catalog of
instrumentation specification sheets, current.
A-9
-------
APPENDIX B
SOME SOURCE REFERENCES - COMMUNITY NOISE ABATEMENT PROGRAM
B-l
-------
APPENDIX B
SOME SOURCE REFERENCES - COMMUNITY NOISE ABATEMENT PROGRAMS
Many of the following documents can be purchased through the U.S.
Government Printing Office (GPO), Mashington, D.C. 20402, Phone: 202/
783-3238 or the National Technical Information Service (NTIS), U.S.
Department of Commerce, 425 13th St., N.W., Room 620, Washington, D.C.
20004, Phone: 202/296-4348. A GPO or NTIS document number will be
included wi.th the reference in such cases.
Report to the President and Congress on Noise, U.S. Environmental Pro-
tection Agency, Office of No'ise Abatement and Control, Washington,
D.C. 20460, EPA Document No. NCR 500.1, December 31, 1971. (GPO
Stock No. 5500-0040) (NTIS No. PB-206 716).
Noise Control Act of 1972, Public Law 92-574, 92nd Congress, H.R.
11021, October 27, 1972, 86 Stat. 1234.
EPA Noise Control Program Progress to Date, U.S. Environmental Protec-
tion Agency, Office of Noise Abatement and Control (AW 471),
Washington, D.C. 20460, March, 1977.
Toward a National Strategy for Noise Control, U.S. Environmental Pro-
tection Agency, Office of Noise Abatement and Control, Washington,
D.C. 20460, April, 1977.
Public Health and Welfare Criteria for Noise, U.S. Environmental
Protection Agency, Office of Noise 'Abatement and Control, Wash-
ington, D.C. 20460, EPA Document No. 550/9-73-002, July 27, 1973.
(GPO Stock No. 5500-00103) (NTIS No. PB-241 0 00/AS).
Information on levels of Environmental Noise Requisite to Protect
Public Health and Welfare with an Adequate Margin of Safety, U.S.
Environmental Protection Agency, Office of Noise Abatement and
Control, Washington, D.C. 20460, EPA Document No. 550/9-74-004,
March, 1974. (NTIS No. PB-239 429/AS).
Report on Aircraft/Airport Noise, U.S. Environmental Protection
Agency, Office of Noise Abatement and Control, Washington, D.C.
20460, EPA Document No. Senate 93-8, August, 1973. (GPO Stock
No. 5270-01936).
Effects of Noise on People, NTID 300.7, U.S. Environmental Protection
Agency, Office of Noise Abatement and Control, Technical Document,
December 1971. (GPO Stock No. 5500-0050) (NTIS No. PB-206 723).
Community Noise, NTID 300.3, U.S. Environmental Protection Agency,
Office of Noise Abatement and Control, Technical Document, December
1971. (GPO Stock No. 5500-0041) (NTIS No. PB-207 124).
B-2
-------
Fundamental of Noise; Measurement, Rating Schemes and Standards, NTID
300.15 U.S. Environmetal Protection Agency, Office of Noise Abatement
and Control, Technical Document, December 1971. (GPO Stock No. 5500-
0054) (NTIS No. PB-206 727).
Model Community Noise Control Ordinance, U.S. Environmental Protection
Agency, Public Information Center, (PM215), Washington, D.C. 20460,
EPA Document No 550/9-76-003, September, 1975.
Guidelines for Developing a Training Program in Noise Survey Technique,
U.S. Environmental Protection Agency, Office of Noise Abatement and
Control, EPA Document No 550/9-75-021.
Noise Control (Any one of the following publications offers information
oh noise control techniques).
- Guidelines on Noise, American Petroleum Institute, Committee on
Medicine and Environmental Health, 1801 K St., N.W., Washington,
D.C. 20006, Medical Research Report EA 7301, 1973.
- Industrial Noise Manual, 3rd edition, American Industrial Hygiene
Association, 66 Miller Rd.-, Akron, OH 44313, 1975.
- Industrial Noise Control Manual, U.S. Department of Health,
Education, and Welfare, National Institue for Occupational Safety
and Health, Cincinnati, OH 45202. HEW Publication No (NIOSH)
75-183, June 1975. (for sale by GPO).
- Berendt, R.D., Corliss, E.L.R., and Ojalvo, M.S., "Quieting: A
Practical Guide to Noise Control," National Bureau of Standards,
Washington, D.C. 20234, NBS Handbook 119, July 1976. (GPO Stock
No. 003-003-01646-2).
- Harris, C.M., Handbook of Noise Control, McGraw-Hill Book Co.,
N.Y. 1957.
Periodicals - Community Noise Abatement program personnel should also
consider subscribing to anyone or all of the following periodic publications:
- Sound and Vibration a monthly magazine published by Sound and
Vibration, 2701 E. Oviatt Rd., Bay Village, OH 44140.
- Noise/News, a bimonthly newsletter of the Institute of Noise Control
Engineering, published by Noise Control Foundation, P.O. Box 3469,
Arlington Branch, Poughkeepsi, N.Y. 12603.
- Noise Regulation Reporter, a private circulation publication, The
Bureau of National Affairs, Inc., 1231 25th St., N.W. Washington,
D.C. 20037.
B-3
------- |