PB82-243981
Noise Effects Handbooks
A Desk Reference to Health and
Welfare Effects of Noise
(U.S.) Environmental Protection Agency
Washington, DC
Jul 81
UH Departmsnf of Commerce
Technical Information Service
-------
EPA
EPA 550/9-82-106
NOISE EFFECTS HANDBOOK:
A Desk Reference to Health and Welfare
Effects of Noise
By Office of Che Scientific Assistant
Office of Noise Abatement and Control
U.S. Environmental Protection Agency
October 1979, Revised July 1931
-------
REPORT DOCUMENTATION >• REPORT NO. 2.
PAGE EPA 550/9-82-106
4.
7.
9.
12
IS
Titli and Subtitle
NOISE EFFECTS HANDBOOK: A DSEK REFERENCE TO HEALTH
AND WELFARE EFFECTS OF NOISE
Author<>)
Performint Organization N«m« and AddreH
SCIENTIFIC ADVISOR'S STAFF
EPA/ONAC
. Spontorln« Organization Name and Addntu
ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF NOISE ABATEMENT AND CONTROL
WASHINGTON D.C. 20460
3. RtclpUnf 1 Accession No.
?B!!2 24398 1
i. Report Data
JULY 1381
c.
>. Performing Onfanlzatlon Rapt. No.
10. PTTj|act/T.«l./Work Unit No.
11. Contract(O or Grant(G) No.
. Oaacrtptorm
NOISE ABATEMENT
NOISE CONTROL
HEALTH & WELFARE EFFECTS OF NOISE
EFFECTS OF NOISE
b. Idafftlflart/Opan-Cndaxl Tarmt
c. COSATI fleld/Oroup
11. AvillaWlrty *t*tam«f<;
NTIS
NANCO
1». Security Cla*a (TMi Maoort)
UNCLASSIFIED
a WWoMMS>C*f)
21. No. of r««w
130
22. Price
(SeeANSl-IM.lt)
-------
DESK REFERENCE
TO HEALTH & WELFARE EFFECTS OF NOISE
TOPICAL OVERVIEW (SEE ALSO INDEX, SECTION 12)
1. The National Moise Problem
2. Hearing Loss; normal auditory function, hearing .loss criteria,
presbycusis, hearing conservation, hearing impairment formulas
3. Nonauditory Physiological Response: stress, arousal response, cardio-
vascular effects, effects on the fetus
4. Communication Interference: factors that affect speech interference,
masking, measurement of masking and speech interference, levels and
criteria, special populations, overcoming speech interference
5. Performance Interference: detriments of interference; qualities of noise
and their relationship to performance interference; noise-sensitive tasks;
effects on children; positive effects; and injury rates
5. Sleep Disturbance; falling asleep, awakening, arousal and sub-awakening
effects; criteria; noise and non-noise factors; other considerations
7. Subjective Response: (individual, psychological responses): special
populations, coping behavior, antisocial behavior, decrease of helping
behavior
3. Community Response; criteria, activity interference, predictors of
community annoyance, relation to population density, urban survey
findings
9. Health and Welfare Analysis: how i: is carried out in regulatory
development; fractional impact; level-weighted population
10. Summary of Hunan Effects of "oise fiora Various Outdoor Noise Levels
11 . References
i;. Index
-------
THE NATIONAL NOISE PROBLEM
Since 1973, Che Department of Housing and Urban Development (HUD) (39)* has
conducted an Annual Housing Survey for the Census Bureau in which noise has been
consistently ranked as a leading cause of neighborhood dissatisfaction. In fact,
nearly one-half of the respondents each year have felt that noise was a major
neighborhood problem (see Figure 2-1). In the 1975 survey, street noise was
mentioned more often than all other unwanted neighborhood conditions. This
survey has also shown that aircraft and traffic noise are leading factors in
making people want to move from their neighborhoods. Approximately one-third of
all the respondents who wished to move because of undesirable neighborhood
conditions, did so because of noise. (39)
HEAVY TRAFFIC "is
STREET REPAIR 21:
?
FIG. 1-1. ^DESIRABLE NEIGHBORHOOD CONDITIONS
FOR HOMEOVNKRS AMD 3ENTZRS: U7IITSD
STATES COMPAS.XTIVE RANKING, 1975.
SOURCE: Ref. 4, pp. 3-12.
References are listed in Section 11, e.g.: (Ref. 39).
1-1
-------
Both a poll conducted by the Gallup Organization in November 197S for the National
League of Cities and a Harris Survey for the ABC network in January 1979 on
attitudes toward environmental issues indicated that the public views noise
as a growing problem warranting more governmental attention and action.
How aany people are estimated to live in residential areas with noise levels
above recommended limits?
According to the Levels Document, the day-night sound level of residential areas
should not exceed 55 d3 to protect against activity interference and annoyance
(5). It is estimated that well over 100 million people, nearly half the U.S.
population, live in areas where the noise exceeds this level (see Figure 1-2).
Twelve million people are estimated to live in areas where the outdoor L,
-v
-------
300
^
O
0
ons
'£ 10
_{_ ^Estimated Rural Areas
on
D
a.
o
a.
O)
>
^
ITS
2
5
0
•
20
^V—Total
£ 1
U»* ;
—
w
\\ %
\0
^-Aircraft :
ncrement:
Urban Noise-
Freeway Increment
I
30 40
50 60
dn
70
80 90
FIG. 1-2. RESIDENTIAL NOISE ENVIRON>EN'T OF THE NATIONAL
POPULATION AS A FUNCTION OF EXTERIOR DAY-NIGHT
AVERAGE SOUND LEVEL.
SOURCE: Ret. 5
What is the JQSC pervasiva enviroanental aoisa source and how many oeoole are
exposed to ic?
As shown in Table 1-1, urban traffic is by far the aost pervasive outdoor
residential noise source, although aircra.ft noise is a significant source as
1-3
-------
well. Over 96 nil lion persons are estimated to be exposed, in and around Cneir
homes, Co undesirably high traffic noise levels exceeding Ldn > 55 dB. Figures
contained in Table 1-1 for each source represent the number of people exposed at
or above a given level (L, ) for the source in question and do not take into
dn
consideration that an individual may be simultaneously exposed to more than one
source culminating in a higher total exposure.
L
dn
(dB)
80
75
70
65
60
55
Number of People in Millions for Each Noise Category
Urban
Traffic
0.1
1.1
5.7
19.3
46.6
96.8
Aircraft
0.1
0.3
1.3
4.7
11.5
24.3
Rail
_
-
0.8
2.5
3.5
6.0
Industrial
_
-
-
0.3
1.9
6.9
TABLE 1-1. SUMMARY OF THE NUMBER OF PEOPLE EXPOSED TO VARIOUS
LEVELS OF L, OR HIGHER FROM NOISE SOURCES IN THE
dn
COMMUNITY'.
SOURCE: Re f. 7
What are typical noise exposures for people throughout the day for various U . S .
life styles?
This information is not precisely known. However a study by Schori seems to show
an average exposure of L ,,4) » 75 d3. However, his sample is not necessarily
typical (8).
-------
How many workers and non-workers are exposed tc noise levels which nay be
damaging to their hearing?
An estimated 15 million American workers are exposed Co an L ,„.. of 75 dB or
aq (a;
above which may be hazardous to thsit hearing. Because of the overlap between
persons in occupational and non-occupational noise exposure situations, there is
an estimated total of 20 to 25 million persons who may possibly incur hearing
losses based on an L ,„, of 75 d3 or above (7).
eq (8)
What Alight be considered the typical daily noise exposure pattern?
Figure 1-3 hypothetically depicts an example of what might be considered a
typical daily noise exposure of a homemaker, students, and workers.
1-5
-------
90
80
70
I 50
40
30 —
Factory
Urban
Environment
Suburban
Environment
* •
L
Play Outside, Shoo
(Urban)
Play Outside, Shop
(Suburban)
Work. Play in Home
Classroom
Office
3
Q
I
>
x-C
ill
12 3
Midnight
0 3
ifmH&
K gii;<
9 12
Noon
9 12 15
18
9 12
Midnight
9 24
FIG. 1-3. HYPOTHESIZED LIFE STYLE
WISE EXPOSURE PATTERNS.
1-6
-------
HEARING LOSS
NORMAL HEARING
How does the hunan ear work?
The Figure 2-1 shows a schematic diigram of how the hunan ear functions,
FIG. 2-1. A SCHEMATIC DIAGRAM OF HOW THE HUMAH
EAR FUNCTIONS
Sourca: Ret. 11
The outer ear consists of the auricle or pinna [1 not shown] and the auditory
canai [21. Tha pinna of the hunan ear is a residual structure although it aav aid
in the localization of sound entering the ear. The sound wave entering the ear is
enhanced by resonant characteristics of the auditsry canal (12).* Sound
waves travel up the auditory canal [2J and set up vibrations ir. the eardrun or
tympanic -aerabrane (3 J.
* References are listed in Section 15, e.g.: (Ret. 12).
2-1
-------
Behind the tympanic membrane is a cavity called the middle ear. The middlo ear
functions as an impedance matcher.* Specifically, sound pressure from waves
traveling through the air (low Impedance) is amplified about 21 times so that it
may efficiently travel into -lie high impedance fluid medium in the inner ear.
This is accomplished by the leverage action of the three middle ear bones: the
malleus, incus, and stapes [4]. The footplate of the stapes, in turn, moves in
and out of the oval window [5l.
The movement of the oval window sets up motions in Cha fluid [6] that fill the
inner ear or cochlea. Movement of this fluid causes the hairs that are immersed
in fluid to move [7]. The movement of these hairs stimulates the calls attached
to them to send impulses along the fibers of the auditory nerve [8] to the
brain. The brain translates these itnnulses into the sensation of sound. (12)
'•mat is considered to be normal hearing?
The ability to hear means being capable of detecting sounds within the frequency
range of 15-20,000 Hz. The threshold of audibility or the point at which sounds
are baraly detectable is shown in Figure 2-2. In clinical hearing assessment,
normal hearing falls within a range of 0 to 25 d3 of the threshold of audibility.
Impedance is comprised of frictienal resistance, mass, and stiffness, and thus
acts in opposition to the incoming sound wave.
-------
I 110
r~i i Qf
° so
T 60
-j <0
o
2 20
o.
"? o
20
100
500
2K 5K 10<
liequency Ht
FIG. 2-2. AVERAGE THRESHOLD OF HEARING
Source: Ref. 12, p. 12.
At what level is the threshold of pain?
The threshold of pain is located at trie upper boundary of audibility and in
normal hearers is in the region of 135 dB for all frequencies (13).
Are there differences in normal adult hearing based on sex?
Starting in the early taenage years, and particularly in the age range of 25 to
65, women i.i industrial countries have batter hearing than do men. However, the
rate of hearing loss in men over 50 declines while that of women of the same age
increases. Above 75 years of age the difference in hearing between the sexes
tends to become insignificant. These differences most likely exist because noise
exposure is primarily greater for men due to the occupational noise they usually
encounter in their early and middle years (14).
2-3
-------
Are there differences in normal adu_l_c hearing based on age.
The threshold of hearing rises (haring becomes less sensitive) with age. This
effect involves primarily, and is most marked at, the higher frequencies above
3000 Hz (14). Studies of large population samples have shown thaC this loss
begins at around age twenty and increases with each decade (13). Refer to Figure
2-7 which shows curves representing changes in the average threshold of hearing
with age for aales and females. (Also see section on Presbycusis. )
Are there differences in normal adult hearing based on race?
There is no inherent difference in hearing levels between the races that make up
the population of the U.S. Human ears are essentially the same around the world.
Any demographic differences that have appeared in some _studies may be
attributable to differing environmental noise exposures. (15)
How is hearing measured?
Hearing is commonly measured by the use of a pure-tone audiometer. Test tones
are produced by the audiometer at known intensities and are presented to the
subjects' ears through earphones. This is known as air conduction testing. Each
ear is tested separately and commonly at the following test frequencies: 250,
500, 100:, 2000, 4000, and 8000 Hz. At each test frequency, the hearing
~~Cf>
threshold for that test tone is identified as the lowest level of tone^which the
subject responds correctly at least 50 percent of the time (13). Hearing level
is reported as the difference between the sounr. pressure level (S?L) of the
measured hearing threshold for the subject and the SPL for a "normal" or
"average" subject as defined in Figure 2-2 on page 2-3. The results are
plotted on an audiogratn. The sample audiogram shown in Figure 2-3 reflects
hearing level ranging from 45 dB at 250 Hz to 25-35 dB at 8000 Hz. Each ear is
represented separately (0 = right, X = left). The modified brackets indicate
bone conduction thresholds; (<= right, > = left).
2-4
-------
•0
OS
40
v»
« 30
•v
z
j 60
M
g 70
a „
X 80
90
110
HS£Ql.T.ia IS MEST2.
250 500 icoo ^ooo i-onn a^nn
/
^
S
.
>
^=1
,
\
y
) —
<
— c
>
\
'
>
x
<
\
^*7
>
^
•) —
— c
/
)
-10
0
0
30
0
70
no
0 200 1000 2000 4000 SOOO
FIG. 2-3. SAMPLE AUDIOGRAM
Source: Ref. 13
HEARING LOSS
VhaC different types of hearing loss are there?
There are Cvo major types of hearing loss: conductive and sensori-neural . A
conductive loss is usually associated with the outer or niddle ear. This kind of
loss is usually caused by a perforation or infection in the aiddla ear or an
inf laoraat ion of th3 middle ear bones. This loss blocks transmission of sound to
the cochlea or inner ear. Conductive losses are correctable by surgery.
-------
A sensori-neural loss results from damage to Che cochlea or neural structures of
the ear. Birth defects, noise, ototoxic drugs, fever, or trauma may cause this
type of loss. Sensori-neural losses are not medically correctable. In addition,
sensori-neural hearing loss can be classified in several ways: noise-induced,
presbycusis, sociocusis, or due to birth defects, congenital problems, disease,
injury, or drugs.
Hew is the type of hearing loss determined?
If air conduction testing indicates that a hearing loss exists,- it is necessary
to determine whether it is of the conductive or sensori-neural type through bone
conduction testing. To do this a bone-conduction vibrator is attached to the
mastoid process of the skull just behind the ear. Test tones are presented at
differing intensities just as with tones presented through earphones. Again each
ear is tested separately. Often a masking tone has to be applied to the untested
ear to ensure that responses are heard only by the test ear. If the hearing
threshold determined by bone conduction testing is essentially normal, the
hearing loss indicated by air conduction is of the conductive type. If the
threshold for bone conduction is consistent with Chat determined by air
conduction, the hearing loss is of the sensori-neural type. A mixed loss exists
if there is a sensori-neural loss with a superimposed conductive loss. (16)
Can conductive losses be caused by noise?
Yes. Rupture of the ear drum and disturbance of the middle ear bones can result
from a very high amplitude impulse or blast. This is often called traumatic
hearing loss. The maximum conductive loss is usually around 50 to 60 dB. (12)
2-6
-------
What are some common causes of sensori-neural hearing loss in newborn babies?
Most babies born with hearing impairments have sensori-neural hearing losses.
These can be either congenital (genetically inherited from the parents) or due to
damage to the embryo in utero. Certain diseases such as rubella (German measles)
or influenza that the mother contracts during pregnancy can result in a sensori-
neural hearing loss as a birth defect in the child (13).
What diseases can lead to sensori-neural hearing loss?
Diseases such as measles, mumps, scarlet fever, diphtheria, whooping cough,
influenza, and certain other viral infections can lead to sensori-neural hearing
loss. The processes of these diseases can have a toxic effect on the sensitive
nerve endings in the crchlea. Infections of the cerebrospinal fluid such as
meningitis can also cause damage to the cochlea. Tumorous growths near the
auditory nerve can cause sensori-neural hearing loss due to pressure on the
nerve. (13)
Can drugs lead to sensori-neural hearing loss?
High doses of ototoxic drugs such as quinine, dihydro-streptomycin, neomycin, and
kanamycin can have toxic effects on the cochlea and cause subsequent sensori-
neural hearing loss (13). The use of these drugs is now restricted.
Vhat is the extent of hearing loss anong the U.S. population?
Based on the audiometric results in 1960-62 Public Health Survey, it is estimated
that approximately 19 aillion Americans or 13 percent of the U.S. population have
hearing losses that can be described as handicapping. Criteria recommended by
the National Institute of Occupational Safaty and Health (NIOSH) (25 dB HL
averaged at 1000, 2000, and 3000 Hz) as the beginning point of handicap was used
2-7
-------
Co derive these estimates. The population suffering such losses increases with
age and the number of people significantly accelerates after age 40.
Information gathered by EPA and the National Association of the Deaf show that
13,362,842 Americans of all ages have some typo of hearing impairment, from mild
to severe. One-half of these people are age 65 or older. There are 6,548,842
Americans of all ages with significant bilateral damage. There are 1,767,046
Americans of all ages that are deaf. Of these, 410,522 are prevocational (prior
to age 19) and 201,626 are prelingual (prior to age 3). The prelingual figure
essentially represents those who were born deaf. Three out of every 100 school
children have some type of hearing impairment and 30 out of every 1000 Americans
age 65 or older have a hearing loss. In 1971 the U.S. Public Health Service
conducted a survey which found that hearing impairment is the moat frequently
reported health problem in the country, with seven out of avery 100 people
reporting a hearing problem. (19)
NOISE INDUCED HEARING LOSS
Vhat is Noise-Induced Permanent Threshold Shift (NIPTS)?
NIPTS is a permanent shift in the hearing threshold (a lowering of the
sensitivity) of the ears due to exposure to noise. It is a sensori-neural type of
hearing loss, and is not reversible (14). NIPTS can result from either a
single exposure to high intensity impulsive noise such as blasts or explosions,
or to longer exposures to lower, but still damaging noise levels. Typically,
hearing loss due to noise exposure occurs first at the higher frequencies,
particularly around the 4000 Hz level (3000 - 6000 H=) (13/54). Figure 2-4 shows
an example of NIPTS relative to exposure levels of 87-102 dB (17).
2-8
-------
s§
£x
PS
2p
52
— O
y
-T^~
Lt?osrai
i
> 1 TLUl
S- 9 TE/UiS
5-19 YIAXS
5-29 TTAJIS
5-39 TIAiU
•••-^-^•.7
^--
v.^-
\
\
\
\
\
1
• —
\
\
\\
>, \
\ \
\
\
\
„, 's
/
/
/
/ .
/ /
y/
/
/ 1
/,
/
/
'r /
/
:s 250 300 u :K 3* tic OK si
is cra£s PSS SECOND
FIG. 2-4
What type of relationship exists between hearing loss and the level and duration
of noise exposure?
In general, Che magnitude of noise-induced hearing loss depends upon the noise
levels to which the ear has been habitually exposed, the length of time for which
it has been exposed to those levels, and the susceptibility of the individual.
Short-term (time in minutes) to high intensity noise, or long-term exposure to
noise of lesser intensity, may cause temporary or permanent hearing loss. With
an adequate time before the next noise exposure, the ear will generally recover
to a previous pre-exposura threshold. Repeated noise exposures without adequate
time for recovery between exposures can lead t; a Noise-Induced Permanent
Threshold Shift (NIPTS). (See References 18 and 20 for a general discussion.)
What factors can increase a person's susceptibility to noise-induced hearing
loss?
A significant factor that is known to increase Che likelihood of noise-induced
hearing loss is continued exposure to hazardous noise. Defects or diseases of
the ear ara hypothesized to cause a predisposition to noise-induced hearing loss
(14). Some evidence exists that persons are especially susceptible to suffering
2-9
-------
hearing damage from noise when they are going through physiological change, or
are enduring physical stress such as rapid growth or illness (20).
Does noise act svnergisticallv with drugs on hearing? Are there other kinds of
synergistic effects?
There is some evidence in the literature which suggests that ototoxic drugs such
as kanamycin, and a class of antibiotics known as aninoglycosides may cause more
severe damage to the ear when treatment with these drugs occurs concurrent with
noise exposure (21). However, only little research has been done in this area,
and the data are limited to animals.
Continuous noise may also interact with impulse noise and body vibrations to
exacerbate hearing loss, although the magnitude of this effect is not exactly
What factors protect the aar against noise-induced hearing loss?
There are several factors which can mitigate the risk of noise-induced hearing
loss. The acoustic reflex (tightening of the oss?'cular chain due to contraction
of the muscles in the middle ear in response to high level sound) protects
hearing from noise exposure to a very limited degree. The use of hearing
protection such as earplugs or eanauffs reduces the risk of hearing damage from
noise. Avoidance of noisy areas, limiting exposure to short periods of time, or
ensuring intermittent rather than continuous exposure will mitigate the risk of
hearing loss from noise. Increased public awareness of the dangers of hearing
damage from noise can lead to the use of ear protectors and the avoidance of
dangerous noise exposure. (14)
2-10
-------
What effect does sex have on the susceptibility to noise-induced hearing loss?
Based on the results of existing r3search, it is not possible to Conclude whether
the sex of the noise-exposed person increases or decreases the risk of noise-
induced hearing loss.
What is the physiological basis for noise-induced hearing loss?
The following mechanisms are considered to play a role in causing damage to the
sensory cells of the inner ear:
o Destruction of cochlear tissue b .ause of the physical force of the
sound pressure.,
o Cardiovascular factors resulting from diminished blood supply to the
cochlea during noise exposure,
o Alteration of fluid transport across Reissner's aerabrane during noise
exposure,
o Alteration of biochemical processes during noise exposure.
(49)
The hair cells normally convert the mechanical energy of sound vibrations into
nevro-electrical signals that are transmitted to the brain. As the intensity of
the noise or the time for which the ear is exposed is increased, a greater
proportion of the hair cells are Jamaged or destroyed. Figure 2-5 schematically
shows the progressive destruction of the hair cells due to excessive noise
exposure.
2-11
-------
Teclonal Vembrint
« Fib«n
(A) NORMAL ORGAN OF CORTI
3 Outer Hjir C«llj Absent
\\\
Oinorrrd
Pillif C*(l Swollen
Sopponing Cctls
(B) PARTIAL INJURY
Colljpw of Organ of Com
Hair Cells Absent — Accruory
C*Mt Swollen i
-------
What is the "Equal Energy" hypothesis?
The "Equal Energy" hypothesis is another way to attempt to predict NIPTS. The
hypothesis rtates that equal amounts of sound energy will cause equal amounts of
NIPTS regardless of the distribution of the energy .across time (18). this
means that the hazard to hearing is determined by the total energy (product of
sound level and duration) that enters the ear on a daily basis. The "Equal
Energy'1 rule allows a 3 dB increase in sound pressure level for each halving of
the duration of continuous daily steady-state noise exposure (14 )•
In determining permissible exposures for the workplace to prevent NIPTS, OSHA
adopted a 5 dB per doubling rule to account for various breaks in noise levels
which occur during the day (25).
EPA has identified an L ,„.,. of 70 dB as the maximum 24-hour exposure necessary
to protect hearing. If ex-osure time is reduced to 8 hours, a maximum u ,.., of
75 dB, a 5 dB increase, has been identified as a protective level for hearing
(5 ).
IMPULSE NOISE
What is impulse noise and what are its effects on hearing?
This is noise characterized by a short duration, abrupt onset and decay and high
intensity. Impulse noise describes the kinds of sound made by explosions, drop
forge impacts, and the discharge of firearms. Exposure to impulse noise aay
result in temporary and permanent shifts in the threshold of hearing (22).
-------
What are the criteria for impulsive noise inside and aws• from the workplace?
OSKA regulations define impulse or impact noise as "sound with a rise time of not
more than 35 milliseconds to peak intensity and a duration of not more than 500
milliseconds." The regulations specify that employees shall not be exposed to
impulse or impact noise which exceeds 140 dB peak pressure level. (25)
The Committee on Hearing, Bioacoustics, and Sioir.echanics (CHA3A) of the National
Academy of Sciences has also recommended damage risk criteria for impulse noise.
The CHABA impulse curve is based on peak sound pressure level and the duration of
the impulses. Figure 4-6 shows the criteria currently in use, assuming an
exposure of 100 impulses per day. The A-duration is the time that the impulse is
initially within 20 dB of the peak level. The B-duration measures the total time
that the sound is within 20 dB of the peak level. The B-duration also accounts
for any reflections or reverberation that may be present, and thus allows less
exposure under these conditions. A correction factor for daily exposures other
than 100 impulses is provided (74).
165
160
UJ
CE
<
UJ
Q-
15C
145
140
135
^v^ A-DURAT1CN
1
0.1
I I
1 10
DURATION - MSEC.
100
1000
•IG. 2-6. BASIC LIMITS FOR IMPULSE NOISE
EXPOSURE ASSUMING 100 IMPULSES
PER DAY AMD OTHER CONDITIONS Ail
STATED III THE TEXT.
Source: Ref. 74.
2-14
-------
PRESBYCUSIS - SOCIOCUSIS
What is prasbycusis?
Presbycusis is a hearing loss associated with increasing age. It is most marked
at higher frequencies, especially those above 3000 Hz. The causes of presbycusis
are believed to be deterioration of the central nervous systea and changes in the
auditory system (12).
What is sociocusis?
Sociocusis is noise-induced permanent threshold shift (loss of hearing
sensitivil/) attributed to environmental noise (hearing loss from nor-
occupational noise exposure) (27). It is difficult to separate sociocusis from
hearing loss due to aging (presbycusis) or to occupational noise exposure.
Exposures to high levels of environmental noise may accelerate loss normally due
to aging (18).
What is the progression of presbycusis with age?
The threshold of hearing rises naturally (hearing becomes less sensitive) with
increasing age. This effect involves primarily the frequencies above 3000 Hz
(14). Figure 2-7 presents data that depict the progression of presbycusis with
age and the degree of loss. As age increases, louses at high frequencies become
greater and hearing loss progresses further down the scale to lover frequencies.
2-15
-------
500 iooo :aoo 3000 icoo sooo
FREQUENCY IN HERTZ
FIG. 2-7. AVERAGE HEARING LOSS FROM AGING FOR >CN AND *OMEN (WITHOUT
THE EFFECTS OF OCCUPATIONAL NOISE)
Source: Kef. 26
2-16
-------
Due to our complex, noisy environment it is difficult, if not impossible, to
separate hearing loss due to aging from noise-induced hearing loss, both from
occupational and environmental noise. Few people live their whole lives in quiet
surroundings. Almost everyone suffers some exposure to damaging noise; either at
home, at work, at leisure, or during transportation between these activities.
The data found in Figure 2-7 are not meant to be taken as an exact prediction of
the magnitude of hearing loss at each age. Different researchers have found
differing values. The figure is presented to represent an average amcjnt of
hearing loss that can be expected. However, it is possible that some of the
hearing loss described in the graph is due to exposure to environmental noise and
not to presbycusis. Some researchers contend that presbycusis consists mainly of
hearing loss due to lifetime exposure to the aggregate of noise found in the
environment. Another view states that environmental noise only accelerates the
losses at high frequencies that would have occurred anyway through aging.
(27)
What evidence exists that sociocusis (hearing loss caused by environmental noise)
Rosen conducted a study of the primitive Mabaans of the African Sudan. Their
environment was almost free of noise with a typical background level of 40 dB (A-
weighted). Among the Mafaaans, the hearing abilities of men in their seventies
and eighties is equal to that of healthy children at age ten. (28)
These findings suggest that the Mabaans show little if any hearing loss due to
aging (presbycusis). The implication of these findings is that much of the
hearing loss observed with age in industrial countries could really be due to
environmental noise exposure (sociocusis) rather than aging (presbycusis).
Rosen's findings may be attributable to diet or other causative factors, and
influenced by difficulties in determination of age.
2-17
-------
Is roc',-, music considered Co be a hearing hazard?
Studies have confirmed that overall sound levels of loud rock and roll, either at
concerts or from domestic stereos, frequently exceed current hearing damage risk
criteria. These noise levels can produce large amounts cf noise-induced
temporary threshold shifts (MITTS) in both the musicians and the listeners.
Sound levels in the area of the band vary from 105-115 dB and in the dance area
from 100 to 110 dB (A-weighted levels), which are within hazardous levels
according to damage risk criteria established by EPA, OSHA, and NIOSH. (29)
Attendance at a rock concert as a fan, or playing and practicing in a rock band,
can impair hearing (30). Figure 2-3 shows before and after audiograms of
musicians and diricers at a loud rock concert (27). NITTS from exposure to the
loud music is clearly visible. Generally, however, the incidence of hearing loss
is not as large as would be predicted (29).
One factor that can lessen the effects of rock music on hearing is its
interrnittency. Rock music is characterized by on-times of approximately three to
five tinutes alternating with off-times of approximately one minute (27).
Another factor is the prominence of low frequency soundjwhich are not as damaging
as high frequency sounds.
so
TEENAGE B4NO
"CUBES! BATING
ItOCX 8 ROLL "USIC
Ill <•» - 1 NOI.«»
TEENAOE OANCERS EXPOSED TO
ROCK a ROLL MUSIC
III «i* - J MOUKl
II • 10
IOOO 200O 3COO »OOO 6OOO
TEST FPEOuEHCT (MI)
5OO :OCC 2COO 200O «OOO 6COO
TEST FBEOUEMCT I Mil
TIG. 2-3. HEARING LEVELS OF TEEN-AGE ROCK-AND-ROLL MUSICIANS AND
DANCERS MEASURED JUST 3EFORE AND 3ET'.-rEEM FIVE TO ELEVEN
MINUTES AFTER A THREE-HOUR "ROCK SESSION" 'vITH AVERAGE
SOU^JD LEVELS OF 112 d3, A-VSIGHT2D. DATA .ARE FROM ?HS
SA.MPLE OBSERVATIONS.
Source: Ref. 27
2-18-
-------
THE CONSEQUENCES OF HEARING LOSS
How is the ability to discriminate and understand speech affected by noise-
induced hearing loss?
Often, the first awareness of hearing loss comes with missing occasional words in
general conversation and having difficulty understanding speech on the
telephone. Many sufferers of noise-induced hearing loss say that speech is
frequently garbled and distorted. Typical noise-induced hearing loss is in the
high frequency range and persons with this type of hearing Ios3 can have normal
or almost-normal hearing up to 1000 Hz. They exhibit little difficulty in
hearing voices at normal intensities but they can have trouble understanding them
especially with noise in the background. This is because consonants are
characterized by high frequencies and weak intensities and vowels by low
frequencies. A person with a noise-induced hearing loss can miss hearing
r.onsonants like £, _f, and £ that givp information and meaning to speech and
language. It is often difficult for people with this type of loss to understand
speech in lectures, meetings, parties, theatres; or on TV, radio, or the
telephone.
What is recruitment?
Recruitment is a rapid increase in the perception of loudness at levels above
hearing thresholds. It is often characteristic of a sensori-neural hearing loss
(13/48) and it may cause discomfort an.' pain. Once a sound is intense enough for
the subject to perceive it, an additional increase in intensity causes a
disproportionate increase in the sensation of loudness. For example, a person
with a 40 dB hearing loss would just barely detect a sound of 40 dB above the
normal threshold of hearing. However, he would hear a sound of 50 dB above the
normal threshold with a Icudness that was greater than that with which a noraal
hearing person would hear a- sound of 10 dB above the threshold of hearing.
(13)
2-19
-------
What is tinnitus and how nany people incur it?
Tinnitus is buzzing, high pitched ringing, or roaring in the head that is a
common complaint of person? with hearing loss, particularly those losses
associated with noise. Tinnitus is often the first recognizable indicator of
hearing damage. It can be in one or both ears, alfhough there may not necessarily
be a hearing loss present. (13)
According to the National Health Examination Survey (1960) 32 percent of the
population or 48 million Americans have experienced some form of I'lnnitus, at one
time or another.
What other effects can hearing loss have?
Hearing loss can lead to reduced employability of the sufferer. It is especially
damaging if children suffer hearing loss during their developmental and
educational years (32). Hearing loss can also be a safety hazard and can
contribute to accidents because warning signals or calls for help can-be missed
by a person with a hearing loss (33).
What are the social consequences of hearing loss?
Many times, friends and associates become less willing to be partners in
conversation or other activities with a person who suffers a hearing loss. It
becomes difficult for a person with a hearing loss to participate in lectures,
meetings, parties, theatres, and other public gatherings; to listen to the TV or
radio; or have telephone conversations. A severe sense of isolation can set in
as hearing decreases. As hearing loss increases so does the sense of being cut
off from the rest of the world. Eventually hearing raay decrease to the point that
the person no longer feels a part of the living world. Emotional depression can
be the result, (12)
2-20
-------
HEARING LOSS CRITERIA
What level has been identified as protective of Che hearing of the general
population in the workplace?
Taking into account that 4000 Hz is the frequency most sensitive to hearing loss
and that losses of less than 5 d3 are generally not considered noticeable or
significant, EPA has identified an 8-hour exposure level not exceeding 75 dB in
order to protect 96 percent of the population frora greater than a 5 dB NIPTS (5).
This recommendation is based on steady noise levels of 8 hours per day, 5 days
per week, over a period of 40 years (5).
What levels have been identified as protective of the hearing of the general
population from significant damage due to environemtal noise?
Environmental noise differs from workplace noise in that it xS generally
intermittent, covers 365 days per year rather than 250 work days, and covers 24
hours per day rather than 8 hours. Taking these factors into account, EPA has
identified an environmental noise level of L ,., •. • 70 dB in order to protect 96
percent of the general population from a hearing loss of greater than 5 d3 at 4000
Hz (5). For details, see Table 2-1.
Leq, 8 hour
Leg, 24 hour
250 day/year
365 day/year
250 day/year
3C5 day/year
Steady
(Continuous)
Noise
73
71.4
63
66.4
Intermittent
Noise
78
76.4
73
71.4
With
Margin of
Safety
75
70
TABLE 2-1. (AT-EAR) EXPOSURE LEVELS THAT PRODUCE NO
MORE THAN 5 dB MOISE-INDUCED HEARING DAMAGE
AT 4000 HZ OVER A 40-YSAR PERIOD
Source: Ref. 5
2-21
-------
If the assumptions underlying this identified level were changed, how would that
affect the level?
o "How would the identified level be affected by a change in the
percentage of the population protected?
Reducing the 96th percentile value to the 50th percentile (i.e.,
protecting half the population) would increase the protective level
value from 70 JB to 77 dB.
o "Since agreement on the value of the intermittency correction is
imperfect, what other values might be used?
The estimated intermittency correction used in the Levels Document is 5
dB. The true intermittency correction is probably within the range 0
to 15 dB.
o "Hov accurate is the equal energy assumption?
The equal energy assumption when applied to the long times (8 hours to
24, or 250 to 365 days) is fairly accurate. It may be suoject to error
when applied to short exposures of extreme level.
o "How meaningful are the basic studies of hearing damage risk?
The probable errors of estimates in the three basic studies cannot be
stated with absolute accuracy. There are a number of problems in
extrapolating percentages of the population damaged from relatively
high exposure levels to the protective level. Also, there is the
problem of determining the amount of hearing damage when the control
(non-exposed) population is subject to high levels of non-occupational
noise. Thus, the 70 dB protective lavel is sinply the best present
estimate, subject to change if better data become available."
2-22
-------
30-1
25-
03
•o
I 20-
35
o
O
»
15-
z
hU
Z
I
a.
O
UJ
O
a
z
O
10-
MAX. NIPTS FOR 4000 H2
AVE. NIPTS FOR 4000 HZ
MAX. NIPTS FOR 500. 1000. 2000 HZ
AVE. NIPTS FOR 500. 1000. 2000 HZ
70
24 MR. A-WE!GnTED SOUND LEVEL IN dB
88
FIG. 2-9. AVERAGE NOISE-INDUCED PERMANENT THRESHOLD SHIFT INIPTS)
IBEYOND PRESBYCUSIC LOSSES1 EXPECTED AS A FUNCTION OF
THE CONTINUOUS A-WEIGHTED EQUIVALENT SOUND LEVEL
2-23
-------
What criterion has been developed for exposure to steady-state noise.
Figure 2-9 shows curves developed from data used in the EPA Levels Document (5)
which depict the maximum and average noise-induced permanent threshold shift
expected averaged over a 40-year exposure to a 24-hour continuous A-weighted
equivalent scund level. For example, over a 40-year (age 20 to 60) exposure to a
continuous A-weighted equivalent sound level of 75 dB, the average noise induced
permanent threshold shift (NIPTS) expected is approximately 4 dB at 4000 Hz.
This means that at age 20, the individual will have hearing equal to the non-
exposed population (0 dB NITPS). At age 60, the individual will have an NIPTS
considerably greater than 4 dB. The average expected shift in threshold is 4 dB.
This change in hearing is caused by the workplace noise exposure. This 13 in
addition to the expected loss of hearing due to aging which at the age of 60 is
approximately an average Loss of 24 dB for each frequency in the range of 250 -
8000 Hz (26). The maximum values indicated in Figure 2-9 show the worst case
expected from the given sound level.
HEARING CONSERVATION
In what ways can noise problems be approached in order to lessen the chances cf
hearing loss due to exposure to noise?
Attempts to solve a noise problem can be made by attacking any combination of the
three basic elements of the problem:
o By modifying the source to reduce its noi.se output
o By altering the transmission path to reduce the noise level reaching
the listener
o By altering the receiver'3 exposure either through limiting the
exposure time or by providing personal protective equipment (11)
2-24
-------
In what ways can a source be modified to reduce its noise output?
Noise sources can be quieted by:
o Reducing inpact or impulsive forces
o Reducing speed in machines, and flow velocities and pressures in fluid
systems
o Balancing rotating parts
o Reducing frictional resistance
o Isolating vibrating elements within the machine
o Reducing noise radiating areas
o Applying vibration damping materials
o Reducing noise leakage from the interior of the machine
o Choosing quieter machinery when replacing appliances (11)
In what ways can the transmission path be altered to reduce the noise level
reaching the listener?
Noi:ie transmission paths can be altered by:
o Separating the noise source and receiver as much as possible
o Using sound absorbing materials
o Using iound barriers or deflectors
o Using acoustical linings
o Using mufflers, silencers, or snu^'ers
o Using vibration isolators and flexible couplers
o Using enclosures (11)
2-25
-------
If it is impossible technologically or unfeasible economically to solve a noise
problem by modifying che source or altering the transmission path, what other
methods can be used to protect the listener from hearing damage?
Limiting the amount of continuous exposure to high noise levels is one approach.
This can bs accomplished either by conducting noisy operations for only short
periods of time or by allowing listeners to be exposed to high levels of noise for
only short periods of time. After all other methods have failed to reduce noise
to acceptable levels, personal hearing protectors can be used as a last resort
where exposure to these high levels is required. (11) Hearing protectors do
not solve the noise problem; they only treat the symptoms of the problem.
How is the exposure of workers to high levels of noise regulated by the Federal
government?
The Valsh-Healey Public Contracts Act of 1938 as amended in 1969 requires that
all companies doing at least $10,000 annual business with Che Federal government
limit the exposure to noise at various levels of their workers to the durations
detailed in the table below. Table 2-2 shows that as the noise exposure level
increases by 5 dB, the allowable tine of exposure is halved. (25)
These same occupational exposure levels were promulgated covering industries
engaged in interstate commerce by the Occupational Safety and Health
Admiristration (OSHA) under the mandate of the Occupational Safety and Health Act
of 1970. In November 1981, OSHA adopted a hearing conservation amendment which
would require industries with an L^ of 85 dB or greater to implement noise ex-
posure monitoring and hearing conservation programs. (99)
2-26
-------
Duration Per Dav
(h)
8
6
4
3
t
1.5
1
1/2
1/4 or less
Noise
Slow
90
92
95
97
100
102
105
110
Level dB
Res pons e
115 max
TABLE 2-2. PERMISSIBLE NOISE EXPOSURES UNDER THE
WALSH-HEALEY PUBLIC CONTRACTS ACT, 1969
Source: Ref. 25
It noise exposure exceeds these limits what additional protective measures do the
OSHA regulations require?
If nois* exposure exceeds these duration and noise level limits, after
economically feasible engineering remedies are exhausted, employees are to wear
hearing protectors issued by the employer (25).
What different types of hearing protectors are available?
Hearing protectors can either be earplugs or muffs. Earplugs can be made of many
materials, such as soft flexible plastic, wax, paper, glasswool, cotton, and
mixtures of these materials. To be effective they must provide a snug, airtight
and comfortable seal. Muff-type protectors cover the entire external ear and
generally provide greater protection than do earplugs. (23) Figure 2-10 depicts
the sound attenuation characteristics of several representative types of hearing
protectors.
2-27
-------
Wix-lmprfgnaied Sloppl«,
Proptrly-Firted Plastic Inseru
I
100
200
500 1000 2000
Tf, Hi (In Cydn p«r Second)
5000
10.000
FIG. 2-10. SOUND ATTENUATION CHARACTERISTICS OF VARIOUS
TYPES OF EAR PROTECTORS
Source: Ref. 23
What other requirenents rausc ba fulfilled under Che OSHA Act of 1970?
The Act requires yearly audiograns for all employees whose noise exposure exceeds
the OSHA limits. In addition, these employees are to be issued hearing
protection devices.
-------
What are baseline and follow-up audiograms and why are they useful?
Baseline or reference audiograms are the results of hearing tests performed on
new employees at their time of hire. Follow-up audiograms are periodic tests
performed to identify any deterioration in the employee's hearing due to on-the-
job noise exposure. Baseline and follow-up audiograms are important because
employers are only liable for hearing loss incurred during the time that a
claimant was employed by them. Baseline audiograms pinpoint the extent of
hearing loss prior to starting work and also can serve as a placement mechanism.
An effort can be made to place employees with an existing hearing loss in areas
that are less damaging to their remaining hearing. Follow-up 'audiograms point
out developing hearing loss problems and determine those susceptible individuals
who are at risk. Their exposures should be modified immediately to protect
against continued deterioration of hearing. The follow-up periodic audiograms
help in pinpointing those individuals needing further testing and in documenting
compensation claims (13).
Why is compensation paid for hearing impairments?
In recent years occupational diseases have become corapensable, and loss of
hearing has been recognized by the Federal government and most states as an
occupational disease. Today, there are some state laws that consider gradual
hearing impairment as a series of traumas or accidents, and therefore ireat it as
a safety rather than a health problem. At the present time nearly all states have
provisions for compensating hearing loss but the statutes vary considerably.
While a few states compensate fairly liberally, some states require "total" loss
of hearing in one or both ears, and others still require proof of disability and
lost wages (34). (For general information and discussion see Reference 38.)
2-29
-------
In terms of compensation and criteria, how are disability, impairment,—and
handicap defined and used?
o Disability: actual or presumed inability to remain employed at full
wages
o Impairment: a. deviation or a change for the worse in either structure
or function, usually outside of the range of normal
o Handicap: the disadvantage imposed by an impairment sufficient to
affect one's personal efficiency in the activities of daily living
Clearly, the term handicap is meant to apply to the compensation situation,
whereas the term impairment is more appropriate to preventive criteria (35). The
x
decision of what is an unacceptable amount of impairment continues to be somewhat
in dispute.
What are :he two most often used hearing impairment compensation formulas?
1. A.MA/AAOO Formula (1973)
This recently revised formula was developed by the American Academy of
Ophthalmology and Otolaryngology. The formula averages hearing loss at 500,
1000, 2000, and 3000 Hz (prior to the revision, the 3 '£Az test frequency was not
used) with a 25 dB low fence below which no hearing impairment is considered to
exist. An average hearing impairment of 92 d3 is considered total hearing loss
with each decibel loss between 25 and 92 dB representing a 1.5 percent impairment
rate of growth (36).
2-30
-------
2. Compensation Formula for Federal Employees (NIOSH Formula)
The original AMA (AAOO) formula was used until 1969. I!: was modified at that time
by the Department of Labor to include test frequencies of 1, 2, and 4 KHz with the
same high and>low fence as before. It was again modified in 1973 to the present
form. This later modification was largely based on NIOSH recommendations in its
criteria document, "Criteria for a Recommended Standard Occupational Exposure to
Noise" (37). NIOSH recommended that hearing impairment should be assessed
by the-ability to hear and understand speech not only in quiet surroundings, but
in everyday conversational settings where significant background noise may be
present. The NIOSH formula averages hearing loss at 1000, 2000, and 3000 Hz,
also using a 25 dB low fence below which no hearing loss is considered. A 1.5
percent hearing impairment rate of growth occurs for every decibel loss above 25
dB. The inclusion of the 3 KHz test frequency while deleting the 500 Hz makes the
_i
formula more sensitive to noise-induced hearing loss since such losses are
incurred initially at higher frequencies. In view of this, a number of states
have incorporated similar high frequency components in their formulas in recent
years.
2-31
-------
NONAUDITORY PHYSIOLOGICAL RESPONSE
EFFECTS - GENERAL
Why is noise considered a health problem?
Noise is generally viewed as being one of a number of general biological
stressors. IE is felt that excessive exposure to noise might be considered a
health risk in that noise may contribute to the development and aggravation of
stress related conditions such as high blood pressure, coronary disease, ulcers,
colitis, and migraine headaches (20)*.
Growing evidence suggests a link between noise and cardiovascular problems.
There is also evidence suggesting that noise may be related to birth defects and
low birth-weight babies (40).
There are also some indications that noise exposure can increase susceptibility
to viral infection and toxic substances (14).
What physiological changes occur in response to noise?
Loud sounds can cause an arousal response in which a series of reactions occur in
the body. Adrenalin is released into the bloodstream; heart rate, blood
pressure, and respiration tend to increase; gastrointestinal motility is
inhibited; peripheral blood vessels constrict; and muscles tense. On the
conscious level we are alerted and prepared to take action. Even though noise
may have no relationship to danger, the body will respond automatically to noise
as a warning signal. (14)
*References are listed in Section 11, e.g.: (Ref. 20).
3-1
-------
Illustrated in Figure 3-1 are possible clinical manifestations of stress
concomitant with noise. Not only might there be harmful consequences to health
during the state of alertness, but research also suggests effects nay occur when
the body is unaware or asleep.
SUMMARY OF POSSIBLE
CLINICAL
MANIFESTATIONS
OF STRESS
CONCOMITANT
WITH NOISE
GALVANIC
SKIN RESPONSE
INCREASED ACTIVITY
RELATED TO
ULCER FORMATION
CHANGES IN
INTESTINAL MOTILITY
CHANGES IN SKELETAL
MUSCLE TENSION
SUBJECTIVE RESPONSE
IRRITABILITY
PERCEPTION OF LOUDNESS
INCREASED SUGAR.
CHOLESTERAL. AMD
ADRENALINE
CHANGES IN
HEART RATE
INCREASED
3LOOu PRESSURE
INCREASED
ADRENAL HORMONES
(CORTICOSTERONE.
COHTISOL)
VASOCONSTRICT10N
FIG. 3-1
How are these physiological responses activated?
Impulses from the brain activate centers of the autonomic nervous system which
trigger a series of bodily reactions as part of a general stress response.
Systems that may be affected include th^ glandular, cardiovascular,
gastrointestinal, and otusculoskelatal systems.
Is short-term exposure to noise considered a health risk?
No. It is generally believed that there is no risk since the body has a chance to
recover. A little stress, as many people will attest, may be beneficial. There
may be exceptions to the above statement. (41)
3-2
-------
Is Long-term exposure to noise considered a health risk?
It is possible Chat repeated or constant exposure to noise can contribute to a
deterioration in health. Whether or not environmental or industrial noise by
itself can lead to chronic disturbances is hard to determine since there are so
many other stresses to which people are exposed (41). This research is
difficult to conduct and little has been done in this area, but research is
accumulating which suggests a relationship between long-term noise exposure and
stress-related health effects, particularly those related to the cardiovascular
system.
Have criteria been established for the nonauditory effects of noise?
Not at the present time. In the past, EPA stated that noise levels identified to
protect against hearing loss should be sufficient to protect against the
nonauditory effects of noise. However, growing evidence suggests that • this
assumption needs to be tested through research. (5) In considering noise as a
general stressor, the need to establish quantitative criteria has now become
evident, given the growing concern about these effects.
NOISE AND THE BODY'S REACTIONS
Why is the investigation of cardiovascular effects so important?
The extent to which noise may contribute to the prevalence of hypertension and
other cardiovascular disorders points to an important public health concern.
Heart disease has been the leading cause of death in the United States for the
past several decades, accounting '.or almost 50 percent of the deaths in this
country. Hypertension is the mosr common of all cardiovascular diseases, and it
3-3
-------
is estimated that from 23 to 60 million Americans, depending on the criteria used
for defining hypertension and the age groups included, have hypertension.
Hypertension is a factor contributing to the death of at least 250,000 Americans
each year. (84) Heart and blood vessel diseases cause a great share of the
financial burden of illness, constituting about one-fifth of the total cost of
illness in this country.
Is there credible scientific evidence which suggests that noise-induced stress
is related to hypertension and cardiovascular disease?
Yes. It has long been known that noise is capable of producing short term
systemic stress reactions in animals and humans. The major question concerns the
extent to which these reactions, if repeatedly elicited, translate into health
problems. Over 40, mostly foreign, retrospective epidemiological studies have
been done assessing the cardiovascular effects of occupational noise. (100,86)
A large number of these studies indicate that long-term exposure to high levels
of occupational noise is associated with increased rates of high blood pressure
and other cardiovascular health problems. Field studies have also been conducted
on various other groups - people living near airports, and school children
exposed to traffic noise - showing that there may be some risk for these people
(66,85). In addition, laboratory studies on animals and humans (42) have
demonstrated a relationship between noise and high blood pressure. It should be
noted that in field studies, while noise may be the major variable between test
and control groups, noise cannot be singled out as the only cause of stress
effects. Attention has to be paid to the type of work being done, other noxious
environmental conditions, and the physical and emotional health of the subjects.
(43)
Ara there any studies which have focused on health effects associated with
community or environmental noise exposures?
Several correlational field studies have examined health outcomes as a function
of exposure to varying levels of traffic and aircraft noise. (66) Although
3-4
-------
these studies must be viewed as exploratory rather than confirmatory, evidence
has been obtained for increased rates of hypertension and cardiovascular
disease, increased usage of various prescription drugs, increased rates of
physician's visits, and increased subjective and self-reported symptoms and
complaints. (86,101) These studies suggest the possibility of adverse health
outcomes associated wirh environmental noise and further underscore the need for
additional research.
Is noise of special ecncern for those persons already suffering from circulatory
and heart problems?
Noise may be potentially mora dangerous to these people since it can aggravate an
existing health problem. There are millions with heart disease, high blood
pressure, and emotional illness who may need protection, from the additional
stress of noise. However.no research exists to document this area of concern.
Are children more susceptible to the physiological stress effects of noise?
The contribution of various environmental factors to the early development of
high blood pressure is an important question. With respect to noise, at least
two studies exist which suggest that exposure to high noise levels in schools and
neighborhoods is associated with elevations in blood pressure. The blood
pressure levels of children living in high noise environments were found to be
significally higher than those of children attending schools or residing in
quieter areas. (96,100,104)
What are some of the findings from the study of blood pressure in laboratory
animals exposed to noise?
Research in this area has been sponsored by EPA. Data from an experiment by Dr.
Ernest Peterson, using monkeys subjected to 24 hours of recorded noise daily
(reprtsenting typical daily noises for an industrial worker), indicate that
3-5
-------
such exposures, repeated daily for months, can cause sustained changes in blood
pressure. This suggests that noise may make a long-term contribution to the
development of cardiovascular disease. (42).
Have any long-term human experimental or other such controlled studies been
conducted?
One long-term laboratory study has been conducted by the Navy. In this study,
subjects were exposed to short bursts of noise at moderate levels over a 30-day
period. (102) Among the results found in this study were statistically
significant elevations in cholesterol and cortisol. Cholesterol is a known risk
factor for cardiovascular disease and cortiso! is a stress hormone. Two other
field studies have been able to obtain high and low noise comparisons on the same
subjects in field settings. (103,86) These studies have reported noise-related
elevations in blood pressure and in various stress-related hormones, and have
found increases in a variety of health disorders and complaints.
* .
Is there a relationship between noise-induced hearing loss and high blood
Studies have been done which have tried to use noise-induced hearing loss as an
indirect index of noise exposure. Ono such study did report higher blood
pressure levels among workers with obvious noise-induced hearing loss. However,
this study has been criticized on methodological grounds and subsequent studies
have yielded mixed results. (43,105)
3-6
-------
With what other stress effects can noise be associated?
Stress can be manifested in any number of ways, including headaches,
irritability, insomnia, digestive disorders, and psychological disorders.
Workers who are exposed to excessive noise frequently complain that noise just
makes them tired.
Quite a few field studies have been done on workers ir Europe, examining the
relationship between noise and illness. In these studies, noise has been related
to the following:
General morbidity (illness)
Neuropsychical disturbances
o headaches
o fatigue
o insomnia
o irritability
o neuroticism
Cardiovascular system disturbances
o hypertension
o hypotension
o cardiac disease
Digestive disorders
o ulcers
o colitis
Endocrine and biochemical disorders
There is a need for additional laboratory replications of these potentially
important findings.
3-7
-------
Do experts agree on the significance of nonauditory physiological effects of
noise?
No. Whil-> a growing body of evidence, provided and accepted by a growing number
of scientists, suggests that noise can be considered a general biological
stressor, not all findings and not all scientists agree. Dr. Karl Kryter (98,
20) performed studies in which his subjects demonstrated relatively small-
physiological changes in response to noise. He feels that the acoustic-vascular
response to noise can be explained by a nonstressful protective auditory system
sympathetic nervous system reflex rather than the general stress response
generally assumed to be responsible for what he believes to be transient
physiological changes observed after noise exposure. So there are differences in
scientific opinion about both the mechanism by which noise affects the body and
the degree to which these effects are stressful. Many of these differences may
eventually be explained in terms of the distinct ways in-which two different
individuals may respond to an identical stimulus.
Have increased illness, accidents, and absenteeism been related to noise?
A study was conducted on the medical attendance and accident files of 500 workers
situated in noisy plants (95 dB or higher) and 500 workers in quieter plants (80
dB or less) in the southeast U.S. Comparing the records of those workers, it was
found that the workers exposed to the higher levels of noise had a significantly
greater rate of accidents, diagnosed medical problems, and absenteeism
(especially in the boiler manufacturing plant where most of the records were
obtained) (86). The study cautions, however, that there may be other conditions
besides noise responsible for these differences.
Does noise have any nonauditory synergistie effects with toxic substances?
There are now 13,000 toxins used in industry and business. Noise as a stressor in
combination with toxins may pose a serious health hazard for workers. However,
no definitive data are available.
3-8
-------
Does noise have an effect on mortality rates?
Some research has been conducted by W. C. Meecham and W. Shaw on the effects of
jet noise and mortality rates around Los Angeles Airpoit. Tne results showed an
effect that is provocative and suggest the need for more in-depth, larger scale
research. Considerable caution should be exercised in generalizing from these
findings since there were many intervening noise exposure and demographic
variables not considered in this ecological-correlation scudy. Therefore the
effects of noise on mortality are still uncertain. (97, 44)
Does protecting against hearing loss guarantee that no nonauditory physiological
effects will occur?
It is not possible to provide a definitive answer to this question at this time.
However, EPA-sponsored primate research has shown that significant and sustained
elevations in blood pressure can be produced as a result of exposure to noise
levels which do not produce any significant permanent hearing loss in the
subjects. (106) These data would suggest that protecting against the auditory
effects of noise dees not necessarily prevent the nonauditory effects. Human
data confirming this conclusion are needed.
Is there a link, between annoyance and nonauditory physiological response to
Although it is reasonable to view annoyance as a symptom or sign of noise-induced
stress, no direst test of this relationship has been made,.
3-9
-------
NOISE AND THE UNBORN
Can noise affect the fetus?
Physiologically, there are reasons to suspect that noise may affect the fetus.
Studies have shovn maternal stress causes constriction of the uterine blood
vessels which supply nutrients and oxygen to the developing baby. Stress may
then threaten fetal development if it occurs early in pregnancy. The most
important period is about 14 to 60 days after conception. During this time,
important developments in the central nervous system and vital organs are taking
place. (45) However, it is presently not known whether noise affects the fetus
in any lasting ways.
As an example of possible outcomes due to fetal noise exposure, a Japanese study
showed a statistical tendency toward low birth weights in noisy areas near a
major airport compared to surrounding areas (40). Other intervening factors that
may have contributed to this finding such as maternal stress have not been
confirmed
#
The U.S. study in Los Angeles found that.in addition to greater incidence of
low birth weights, there vas also a greater incidence of birth defects such as
clefts of the lip or palate, and spinal malformations. These results should be
judged cautiously because of the many correlational problems with the data.
On the other hand, a similar study on fetal birth weight was conducted by
the Center for Disease Control (85). This study found that there were no
effects (46).
3-10
-------
COMMUNICATION INTERFERENCE
EFFECTS
The indirect effects of speech interference are;
o Disturbance of normal domestic or educational activities
o Creation of an undesirable living environment
o Safety hazards
o A source of extreme annoyance (i>)*
Can high background noise levels affect social interaction?
i
For certain individuals who live in noisy areas, the adoption of a lifestyle that
is nearly devoid of communicition and social interaction can result. If noise
interferes with their communication, they stop talking, change the content of
their conversations, talk only when absolutely necessary, and frequently repeat
themselves (31).
How is communication interference important in safety?
Masking of warning signals and directions by other intrusive sounds can be
hazardous. For example, an airlire pilot's reception of an air traffic control
message can be affected by too much background noise. A missed warning in a noisy
steel mill can result in an accident, injury, or even death (47).
* References are listed in Section 11, e.g.: (Ref. 5).
4-1
-------
Can vigilance be disrupted by noise?
Yes, listening for particular signals can be hindered by high background noise
levels, For c.;-vnpls, a parent working downstairs might be listening for sounds
of a child upstairs awakening from sleep. A noisy environment could interfere
with this.
What factors determine "he extent to which noise affects speech communication''
o Location (whether indoors or outdoors).
o The attenuation characteristics of the building and internal
structures wheu indoors.
o The vocal effort and skill of the talkers and listeners.
o The background noise level and spectrum (5).
o Hearing acuity.
Does speech qualify have an effect on speech interference?
If the talker is imprecise in his speech (poor articulation), speaks a different
dialect than the listener, or speaks softer than most, lower background noise
levels are required (14).
Is the duration of the noise a determinant in speech interference?
Intermittent noises will mask speech in variable degrees. Impulse noise in
isolated one-second bursts is unlikely to disrupt much speech communication jue
to the redundancy of speech. However, as the frequency and duration of the noise
bursts increase, so does the masking effect (14).
4-2
-------
Do fluctuating sound levels have any effect on intelligibility?
For a fixed L , sufficient to mask some speech, interference with speech is
eq
greater for a steady noise than for almost all types of environmental noise whose
magnitude varies with tiaie (fluctuating sound levels) (5).
What methods are used to characterize noises in respect to their speech-making
abilities?
o The Articulation Index (AI), a complex measure which accounts for the
differences in masking capabilities of frequencies in background
noise. (91).
o The Speech Interference t.avel (SIL), an arithmetic average of the
octave-band sound pressure levels of noise that affect the major
speech frequencies (octave band sound pressure levels are centered at
500, 1000, 2000, and 4000 Hz). (92).
o A-weighted sound level, which reflects the sensitivity pattern of the
ear's response to noise and speech. (14)
Why is the A-veighted sound level a good measure of speech \nterferenee potential
of noise?
A-weighting gives the greatest weight to those components of noise that fall in
the frequency range where most speech information resides. It gives lass
emphasis to noise in the lower frequency (500 Hz or low
-------
What are the appropriate noise levels Co prevenr speech interference with oral
communication?
For outdoors, Table 4-1 shows distance! between speaker and listener for
satisfactory outdoor speech at two levels of vocal effort in steady background
noise levels. In other words, if the noise levels in Table 4-1 are exceeded, the
speaker and listener must either move closer together or expect reduced
intelligibility. This is also shown in Figure 4-1.
VOICE LEVEL *
Normal Voice ( in dB)
Raised Voice ( in dB)
COMMUNICATION DISTANCE (meters)
0.5
72
78
1
66
72
2
60
66
3
56
62
4
54
60
5
52
58
TABLE 4-1. STEADY A-WEIGHTED SOUND LEVELS THAT ALLOW
COMMUNICATION WITH 95 PERCENT SENTENCE
INTELLIGIBILITY OVER VARIOUS DISTANCES
OUTDOORS FOR DIFFERENT VOICE LEVELS
SOURCE: Ref. 5.
*ASSUMES NORMAL VOICE LEVEL OF 70 dB
(67 dBA) OR RAISED VOICE OF 76 dB (73 dBA)
What criteria are used to predict the effect of noise on speech communication?
For indoors, Figure 4-1 shows that an L, of 50 dB pennies virtually 100 percent
intelligibility within buildings (5). (A given percentage of sentence
intelligibility, such as 95 percent or 100 percent, indicates the proportion of
key words in a group of sentences which are correctly heard by normal-hearing
listeners .)
For outdoors, Figure 4-2 shows that an L, of 50 dB which also indicates nearly
100 percent intelligibility (5).
4-4
-------
Figure 4-3 shows appropriate voice levels limited by ambient noise conditions.
Along the abscissa are various measures of noise, along the ordinate distance,
and the parameters are voice level. At levels above 50 dB people raise their
voice level as shown by the "expected" line if communications are not vital or by
the "communicating" line if communications are vital. Below and to the left of
the "normal" voice line communications are at an AI level of 0.5, 98 percent
sentence intelligibility. At a shout, communications are possible except above
and to the right of the "impossible" area line. (50)
100
I
65 70 75
LEVEL OF CONTINUOUS NOISE CAUSING INTERFERENCE (dB)
FIG. i-l. CRITERIA FOR INDOOR SPT.ECH INTERFERENCE (RELAXES
CONSERVATION AT GREATER THAN 1 METER SEPARATION,
<*5 d3 BACKGROUND IN THE ABSENCE OF INTERFERING
NOISE) SOURCE: Ret. 5
-------
100
CONTINUOUS OUTDOOR NOISE CAUSING
INTERFERENCE (L ), dB
FIG. 4-2. CRITERIA FOR OUTDOOR SPEECH INTER-
FERENCE (NORMAL VOICE AT 2 METERS)
SOURCE: Ref. 5
4-6
-------
XV* DISTANCE NOISE
AREA WHERE UNAIDED
FACE-TO-FACE
COMMUNICATIONS
ARE INADEQUATE
DISTANCE NOISE AREA
WHERE FACE-TO-FACE
COMMUNICATION IN
NORMAL VOICE IS
ADEQUATE
50 60 70
A WEIGHTED SOUND LEVEL
100
FIG. 4-3, NECESSARY VOICE LEVELS AS LIMITED BY AMBIENT
NOISE FOR SELECTED DISTANCES BETWEEN TALKER
AND LISTENER FOR SATISFACTORY FACE-TO-FACE
COMMUNICATION.
SOURCE: Ref. 50, 28
NOTE: The figures are based on data from "sentences known to listeners". As a
result, these levels may not be completely adequate in describing fluctuating
noise conditions and would be conservative estimates for situations where
communication is unpredictable.
4-7
-------
SPECIAL POPULATIONS
Does the age of adults have any ffeet on the ability to discriminate speech in
noise?
The ability to understand partially masked or distorted speech begins to
deteriorate around age 30 and declines steadily thereafter. Generally,
therefore, the older the listener, the lower the background noise must be for
normal communication. (14)
Do people with hearing loss have any special problems with regard to speech
interference?
People with hearing losses require more favorable speech-to-noise ratios than do
persons with normal hearing (14). This means that the difference between the
level of speech and the background noise level must be greater for hearing
impaired individuals than for people with normal hearing. This can be achieved
either by decreasing the background noisr; level or increasing the speech level.
Increased levels of noise, in relation to the speech signal, tend to aggravate
the adverse effects of hearing loss. (48)
What are the effects of noise on children's communication skills?
High levels of noise reduce the number of conversations and their content,
quality, snd fidelity. Children have a relative lack of knowledge of language
that makes them less able to "hear1' speech when some of the cues are lost.
Repeated exposure to high levels of noise in "critical periods of development'1
might affect conceptual development and the acquisition of speech, language, and
language-related skills like reading and listening. (32)
4-8
-------
Can reading ability be affected bv high noise levels?
A study based on the reading scores of children in grades two through five who
live in an apartment building showed that the noise in and around the building
was detrimental to their reading development. The longer the children had lived
in the noisy environment, the lower their reading test scores. (66)
Are these effects only important at home?
Studies have shown that schools located next to expressways or under aircraft
flight paihs also show severe effects on learning. For example in addition to
the length of the disruptive aircraft flyovers, in many cases, considerable time
is spent refocusing the students' attention on the study material (32),
4-9
-------
PERFORMANCE INTERFERENCE
DETERMINANTS OF INTERFERENCE
What noise parameters affect work performance?
The question is a complex one and in any particular case, at least four factors
should be kept in mind:
o Characteristics of the noise
o Characteristics of the task
o Aspects of performance considered important
o Individual differences
In general, noise is more likely to reduce the accuracy rather than the total
tity of work and it affects complex tasks more than simpler ones (,31).* As
the noise level increases, both reaction times and numbers of errors increase.
j
These effects are more pronounced for complex tasks than for simpler tasks. In
fact, for some simple Casks, noise may enhance performance.
How does noise exposure interfere with human performance?
Noise often results in a disruption of one's attentional processes. Cues that
are irrelevant to task performance are dropped out first. If attention is
further restricted, then cues that are relevant to performance of thu task are
eliminated. (96)
Why does performance sometimes improve during exposure to noise?
Performance improves during exposure to noise when distracting cues are dropped
ouc. Task performance improves when only relevant primary task cues are focused
upon. (96)
* References are listed in Section 15, e.g.: (Ref. 31).
5-1
-------
Noise levels most likely to be detrimental Co performance are;
o Continuous noise levels above 90 dB (A-weighted)
o Levels less Chan 90 dB (A-weighted) if they have predominantly high
frequency components, are intermittent, unexpected, or uncontrollable
(5)
Does th° interaittency or predictability of the noise play a role in performance
interference?
Yes, when a noise occurs in a random, intermittent or unpredictable fashion,
errors tend to increase, and greater effort is required to maintain
concentration. Unpredictable noise may lead to breaks in concentration that are
followed by compensating increases in the work rate. Thus, the overall rate of
work may not be affected, but the variability of the work rate may be. (51, 53).
Do high-intensity noises have any special effects on performance?
High-intensity noise such as jet engine noise in close proximity ia reported to
cause nausea, vertigo, uncoordination, fatigue, and mental confusion. These
effects are attributed to vestibular stimulation and to reflexes elicited by
vibration of the skin, muscles, and joints. Any of these symptoms can give rise
to a reduction in performance efficiency. (52)
Does controllability of the noise have an effect on performance?
Noises that are unpredictable or randomly intermittent tend to be associated with
greater decrements in perfomance than in continuous noise. These decrements may
in part be explained by the fact that these noises are perceived by the
individual as being unpredictable.
Recent research (56) suggests that exposure to unpredictable noise may result in
performance decrements which occur after the noise has ceased (after effects).
Does the frequency spectrum of the noise have any effect on performance?
Yes, in general, high frequency noises (above 2000 Hz) impair performance more
than lew frequencies of the same sound pressure level
5-2
-------
Does the meaning of the noise affect its ability to interfere with performance?
Yes, the meaning of the noise is an importart variable. Relevant and meaningful
information is attended to, rather than ignored, thereby detracting from the task
at hand.
What types of tasks can be affected by noise?
o Tasks that involve concentration, learning, or analytic processes
o Tasks where an integral part of performance is speaking and/or
listening
o Tasks requiring fine muscular movements
o Simultaneous tasks
o Tasks which require continuous performance
o Tasks including prolonged vigilance and few signals
o Performance of any task that involves auditory signals
o Tasks requiring attention to multiple channels (20)
How can noise affect learning or information gathering?
Noise may compete for the limited number of channels available for information
input. When the system is already overloaded, the individual must take more time
to evaluate the intruding stimulus, or risk making errors (55).
Do individuals differ in the extent to which noise may interfere with their
performance?
Yec, laboratory studies have shown that some people who have been exposed to
noise are not able to perform tasks requiring skills of retention and attention
to detail. These decrements in performance are especially found in those who are
exposed to uncontrollable or unpredictable noise (56).
5-3
-------
Research has shown that the motivational involven.ent of the individual influences
the extent that noise will have on performance (57). Other studies have
shown that personality variables, primarily the trait of introversion/
extroversion, can influence performance under noise (58; 59; 60).
Can noise have cumulative effects on performance?
It has been hypothesized that exposure to noise can produce an actual change in
the state of the individual that is reflected in failure of selective perception.
This change produces measurable performance decrements (14). More errors
tend to occur toward the end of performance sessions, which also suggests a
cumulative effect by the end of the workday (61).
Can noise have both positive and negative effects on task performance?
Yes, depending on the complexity of the task, noise may either improve or
interfere with performance. Tasks that are mechanical or repetitive, and where
average levels of performance are sufficient, will seldom be affected. Moderate
levels of noise can produce beneficial arousal levels during monotonous tasks.
Tasks requiring moderate meffort seem to be unaffected by the noise. Hizhly
co-jplex tasks requiring attendance to a large number of cues, or to many cues in
rapid succession, may be affected by noise at all levels of intensity.
(62)
Does noise produce any after effects on performance?
Yes, research has shown that noise may produce adverse performance on tasks
performed after the noise is no longer present. These effects sometimes occur
even when performance during noise was not affected. Aftereffects aPPear
likely to occur when the noise has been unpredictable or uncontrollable. (56)
5-4
-------
Is industrial noise considered a problem in performance interference?
Yes, industrial noise may have the most pronounced effects on performance
including exhaustion, absentmindedness, mental strain, absenteeism, tenseness,
and irritability. All of these factors affect worker efficiency. (63) It is
reasonable to suppose that increased absenteeism can come from workers'
psychological aversion to returning each day to an unpleasant, noisy working
environment. The frequency and severity of industrial injuries could tend to be
higher in noisy environments because of masking of warning signals and of
increases in momentary gaps or errors in performance (64 ) •
What is the estimated cost to society of the workplace effects of noise due to
absenteeism, noise-induced industrial injuries, and performance interferences?
o One day per year, worker exposed to greater than 85 dB
o About $250 per worker per day
o With 8 million exposed workers, about $2 billion not including
workmen's compensation (64 ) •
Ara children susceptible to performance effects of noise?
Although there is relatively little laboratory evidence to substantiate
performance degradation, there have been field studies which demonstrate that
high noise levels have been correlated with poor performance on reading rests
(65) and auditory discrimination problems (66). These effects were found • •> have
little to do wich socio-economic class or IQ. The significance of these effects
is particularly important for younger children who through lack of verbal
experience need lower noise levels in which to perform in order to -icv».lop the
basic skills which contribute to cognitive and language development.
5-5
-------
SLEEP DISTURBANCE
Sleep disturbance is one of Che major causes of annoyance due to noise. If it
becomes a chronic problem, sleep disturbance may potentially lead to health
disorders (67)*.
EFFECTS OF NOISE
How does noise interfere with sleep?
Noise, of course, can make it difficult to fall asleep. Noise levels can create
momentary disturbances of natural sleep patterns by causing shifts from deep to
lighter stages. Noise may even cause awakening which the person may or may not be
able to recall. (14)
Is the sleeper aware of all of his bodily reactions to noise?
He can be completely unaware of being affected but can have a disruption of total
sleep quality nevertheless. Subjects often forget and underestimate the number
of times that they awaken during sleep (88). Loud noises can continue to
awaken or arouse the sleeper, but they may become so familiar with the sounds
that they return to sleep very rapidly.
Vhat are the indirect effects of sleep disturbance?
A person whose sleep hss been disturbed severely may feel lethargic and nervous
during his waking hours and aa;' be unable to perform at his usual level of
efficiency (68).
* References are listed in Section 11, e.g.: (Ref. 67).
6-1
-------
FALLING ASLEEP
What noise levels can delay falling asleep?
At levels ot tC f> 50 dB (A-weighted), some subjects have reported difficulty in
falling asleep, frequently taking over an hour. The number of subjects having
difficulty increases as the sound level increases (14).
AWAKENING
What noise levels can cause awakening?
Studies have shown that at levels of 70 dB (A-weighted) or above.behavioral
awakening* will most likely occur (14).
Do noises lasting a long period of time awaken more people Chan shorter noises?
The temporal pattern of exposure (i.e.;short or long duration) has a major effect
on awakenings due to noise. Short signals have to be much higher in level to
awaken as many people as a longer, steady noise. (93, 68)
Are all sounds equally effective in awakening people?
Not all sounds of the same level are equally capable of awakening people. The
character of some sounds causes them to awaken more people than other sounds of
the same level (68, 94).
Behavioral awakening -aeans a specific motor or veibal response (58
6-2
-------
Does the background noise environment in which people are accustomed to sleeping
affect the number of nightly awakenings dje to noise?
People living in higher background noise neighborhoods tend Co awaken less Chan
people living in quieter background noise neighborhoods. (68, 94).
Do people awaken more at some times of Che night than aC ochers?
The awakening effects of noise appear to be related to the time of occurrence of
exposure during Che night. The probability of awakening to noises of the same
level is slightly lower within two hours after retiring than when it occurs later
in the night. (68, 94).
AROUSAL AND SUB-AWAKENING EfFECTS
Vhat st?ges of sleep does poise affect?
Laboratory subjects appear to be most sensitive to acoustic stimuli during the
more shallow stages of sleep. A person typically goes through a cycle of sleep
which becomes progressively deeper, and the stages of this cycle may vary in
length of time. These stages are reflected in EEC measurements. Heart rate
changes, vasoconstriction, respiration changes, electrodennal activity, and
moror responses are all sensitive to noise during sleep. (68)
6-3
-------
CRITERIA FOR SLEEP DISTURBANCE
Do criteria for sleep disturbance include shifts in stage of sleep and
behavioral awakening?
Examples of criteria pertaining to sleep disturbance are displayed in Figures 6-1
and 6-2. These figures, which were adapted from a summary and analysis of recent
experimental sleep data as related to noise exposure (3), show a relationship
between frequency of response (disruption or awakening) and the sound level of an
intrusive noise. In Figure 6-1, the frequency of sleep disruption (as measured
by changes in sleep stage, including behavioral awakening) is plotted as a
function of the Sound Exposure Level, a time-integrated measure referenced to a
one second duration. Similarly, the frequency of awakening is shown in Figure 6-
2. Thus, Figures 6-1 and 6-2 show that the probability of two types of sleep
disturbance, within certain statistical limits, may be predicted by physical
indices of noise exposure.
o
h^
O.
cz.
GO
(/I
u.
o
>•
o
40
50 50 70 80 90 100 110
A-WEIGHTED SOUND EXPOSURE LEVEL
FIG. 6-1. PROBABILITY OF A NOISE INDUCED
SLEEP STAGE CHANGE
6-4
-------
'55 65 "75 '85 95 105 115
A-WEIGHTED SOUND EXPOSURE LEVEL (decibels)
FIG. 6-2. PROBABILITY OF A NOISE INDUCED
AWAKENING
How does sleep disturbance varv with noise level?
Generally, the higher the noise level Che greater the probability of a response
(63). Thiessen found that there was a 5 percent probability of subjects being
awakened by peak levels of 40 dB (A-weighted level) and a 30 percent probability
at 70 dB. If EEC changes are also considered, these probabilities increase to 10
percent at 40 dB and 60 percent at 70 dB (39).
6-5
-------
Do the number of noise peaks have any effect on the ability of the noise to
interfere with sleep?
If the number of sound peaks increases, the person will take longer to fall
asleep even if the average sound level decreases (14). However, continuous
or very frequent noise throughout the night, even as high as 95 dB (A-weighted),
appears to cause little change in the average duration of the sleep stages, since
such stages are disturbed more by peaks that vary widely from the background
ambient level than by high continuous levels alone (68).
Does the quality of the sound have any effect on the ability of noise to interfere
with sleep?
Inherently meaningful sound such as one's name or sound that acquires meaning by
instructions or conditioning can awaken a sleeper at lower intensities than those
required for meaningless or neutral sounds. Unfamiliar sounds may awaken people
at a lower level than familiar ones. (68, 70)
Are the sex and age of the sleeper factors in disturbance of sleep by noise?
Several investigacors have reported that middle-aged women may be less sensitive
to noise during sleep. (69) In general, though, the older the subject, the more
likely he is to respond to noise while sleeping (68). Young children, on the
other hand, appear to be less affected by noise in all stages of sleep (70).
Does the amount of time asleep affect the response to noise?
Arousal is more likely to occur after longer periods of sleep (71),
6-6
-------
Does sleep deprivation have an effect on the disturbance of sleep by noise?
Sleep after prolonged periods of sleep deprivation consists of increased tine in
stages Delta and REM. This causes an increase in the thresholds for arousal and
stage change (63 ) = Overall, sleep-deprived individuals require more intense
auditory stimuli to awaken than do normally rested persons (71).
Is sleep disturbance by noise seen as a problem by the population in general?
Survey data show that sleep disturbance is often one of the principal reasons
given for noise annoyance (14).
Can sleep disturbance cause long-term problems?
Sleep is thought to be a restorative process during which organs of the body
renew their supply of energy and nutritive elements. Since noise can disrupt the
sleep process, it may take its toll on health. (14)
6-7
-------
SUBJECTIVE RESPONSE
Conclusions concerning the factors that determine an individual's subjective,
psychological response to noise are difficult to derive since individuals vary so
much in their reaction to noise. Clearly, more research is needed to assess this
complex topic fully.
MENTAL, PSYCHOLOGICAL EFFECTS
What kind of mental or psychological effects can occur with excessive noise
exposure?
Excessive noise exposure can bring about a wide variety of psychological
responses or symptom? in the individual. A person may respond with anger, or
experience symptoms such as anxiety, irritability, and/or general emotional
stress. Noise may negatively affect work performance because of reduced worker
morale and motivation. D.istraction and poor judgment may result from mental
fatigue. (14)*
Is excessive noise exposure related fo mental illness?
The answer to this remains unsolved. Studies have shown that residential areas
exposed to high noise levels may have a higher incidence of mental illness among
their residents, however the evidence is inconclusive. One study thit examined
admissions of residents ne&r London's Heathrow Airport to a psychiatric
hospital suggests that the prevalence of mental problems was higher in the
population nearest the airport (90). On the other hand, a Swiss study looking at
the mental health status of residents near three Swiaa airports found no
signficant relationship between minor psychiatric illness and noise exposure
(72).
* References are listed in Section 11, e.g.: (Ref. 14).
7-1
-------
What physical qualities of noise affect a person's subjective response?
The physical attributes of noise that can affect an individual's subjective
response include: apparent loudness or intensity, spectral shape, presence of
discrete frequency components, abruptness or impulsiveness, intermittency,
duration, and temporal variations (14).
Besides the physical attributes of the noise itself, vnat other aspects of the
exposure situation affect the individual's response?
Among the factors that affect an individual's response to noise are contextual
factors such as: the time of day, the activity interfered with, the ability to
control the source, and the information content of the noiss. Response may also
be affected by personal factors such as previous experience with noise exposure
or socio-economic and educational status. (14,4,9)
What is the best weighting system to use for analysis of individual subjective,
psychological response?
In most cases, the A-weighting scheme can be used to study individual
response to noise. Figure 7-1 shows how the A-weighting network on a sound
level meter discriminates sounds at different frequencies compared to the B and
C-weightings. A recent study has indicated that the D and E weightings generally
perform somewhat better than A-weighting. Computational schemes, such as
Stevens' Mark VI and Mark VII loudness calculation procedures, Zwicker's loudness
calculation procedure, Perceived Noise Level, etc., are typically superior to the
frequency weightings. In the long run however, none of these other weightings or
calculation schemes need to displace the simple A-weighting which has the added
advantages of ease of use, public acceptance, and reasonable accuracy (73).
7-2
-------
a -15
1-20
-25
> -30
i -35
-4Q
-50
/
Frequency Responses
for Sound Level
Weighting Characteristics
20 50 100 200 500 1000 2000 5000 'O.COO 20,000
Frtqutncy lwi)
FIG. 7-1. FREQUENCY RESPONSES FOR SOUND LEVEL
WEIGHTING CHARACTERISTICS.
What is meant by the teras "phon" and "sone", and what is their application to
subjective response?
Phons and sones are used Co measure or rate loudness (the subjective impression
of the magnitude of a sound). A pnon is the unit of loudness level. It
is intended to be equivalent to the decibel level of a 1000 Hz reference tone
judged equally loud to the sound being evaluated. Figure 7-2 shows equal
loudness contours as a function of frequency which demonstrates the relationship
between loudness level (in phons) and intensity (in decibels).
The sone is a linear measure of loudness. The loudness of one sone equals the
loudness of a 1000 Hz tone at 40 dB sound pressure level. A sound judged to be
twice as loud as a 1000 Hz tone at 40 dB equals 2 sones; half as loud, 1/2 sone,
etc. Generally, in increase of 10 dB is equivalent to a doubling of sona value,
and the judged Icudness. The Stevens method and Zwicker procedure both calculate
sone values of complex wide band sounds.
7-3
-------
a
•3
120
20
500 1000
Frequency
5000 10000
FIG. 7-2. EQUAL LOUDNESS CONTOURS
Are there any particular noises that are more annoying than others?
Sounds of 2 KHz or higher (especially those with discrete frequency components)
are generally the most annoying and disruptive, although noises that are abrupt,
intermittent, or fluctuate with time can be very annoying as well (14). In
general, the louder the nosie the more annoying it is likely to be (14).
Are there any special populations that are particularly annoyed or bothered by
noise?
A number of variables aay affect individual susceptibility to noise. These
include personality factors, psychological factors, state of health, etc.
Special populations that are particularly sensitive have not been identified,
however, and research needs to be performed to identify these groups, if any.
7-4
-------
Does personality play a role in individual response to noise?
Social surveys have indicated wide individual variations in response to noise.
It appears that personality does play some part in a person's subjective response
to noise, although the exact natura of the relationship is too complex to assess
readily. Some studies have concluded that those with a fairly high level of
empathy, intelligence, and creativity uay be more sensitive to noise then most
(75).
Hov do individuals alter their behavior in order to cope with noise?
People may either take direct physical actions or make indirect mental
adjustments to cope with noise. For example, people may spend less time
outdoors, keep their windows closed, take sleeping pills, use earplugs, spend
less time talking and socializing, or complain to government officials. On the
other hand, they might direct their anger at a noise inward and blame themselves
for being bothered by it. They may perhaps deny there is a problem and attempt to
stop responding emotionally to it. They may even project their anger at a noisa
source to a person incidentally associcated with it. (76)
Can noise cause an individual to exhibit anti-social behavior?.
Noise can cause peop;eto exhibit sucn anti-social behavior as aggression and
violence, though they would not normally do so. . Certain extreme
incidents that have been reported, for example, include a business executive
shooting at nearby water-skiers, or a usually quiet, night clerical worker
shooting and killing a child playing outside his appartment. Both examples
provide anecdotal illustrations of effects on behavior presumably attributed to
noise (1*0. There have also been lab studies which show that excessive noise may
reduce social interaction, social responsibility, and verbal disinhibition,
diminish helping behavior, and increase aggressive response. (77, 78, 79)
7-5
-------
Can noise lead Co reduced social interaction and enjoyment?
Besides the obvious impairment in social interaction associated with noise-
induced hearing loss, living in a noisy environment oiay lead to what could be
referred to as a noncommunicative life-style. This is a life—style in which
social interaction is avoided and communication is minimized due to noise
interference (31).
7-6
-------
COMMUNITY RESPONSE
This section concerns average community response to noise as determined by
community surveys, and other measures of annoyance such as complaints.
How does noise annoy?
Noise by definition is unwanted sound. It is an intrusion on one's sense of
privacy. Noise can be an emotional strain and a source of great frustration when
the noise is beyond a person's control. Noise may interfere with a broad range
of human activities, the overall effect of which is to cause annoyance. Such
activities include:
1. Speech Communication in Conversation and Teaching
2. Telephone Communication
3. Listening to Television and Radio Broadcasts
4. Listening to Music
5. Concentration During Mental Activities
6. Relaxation
7. Sleep
To what degree does noise cause neighborhood dissatisfaction?
The HUD Annual Housing Survey (1975, 1976) indicates that noise is the most
frequently cited undesirable neighborhood condition, surprisingly ranking higher
than crime. Noise is often given as the reason for residents wanting to move from
their neighborhoods. (4).*
* References are listed in Section 11, e.g.: (Ref. 4),
8-1
-------
How is community response measured?
Community response to noise is usually studied through social surveys. A number
of social surveys have been conducted world wide to determine the extent of the
noise problem as well as to assess the response of the people to specific noise
sources. These studies attempt to predict, on an aggregate basis, the degree of
annoyance or other effects that can be expected by the community at varying noise
levels. The average response of the community is used because it is very
difficult to predict the response of any given individual.
Are complaints a good indicator of the community noise problem?
Another way of assessing community response is through complaints and legal
actions. However, many other economic, political, and social factors influence
the filing of complaints. So the quantification of complaints cannot be used as
definitive expressions of community response. Figure 8-1 shows the correlation
of community complaint reaction to noise after the noise exposure has been
adjusted for factors such as time of year (windows open or closed), duration and
frequency of intruding noises, presence of pure tones or impulses, etc.
a-:
-------
m Community Reaction
Vigorous Action
Widespread Threati
of Legal Action. Strong
Appeals to Local
Officials to Stop Noisa
Widespread Complaints.
Individual Threati of
Legal Action
Sporadic Complaints
No Overt Reaction
Although Noise is
Generally Noticeable
• • * *** f.
• rt .»-- *
*•!•»•
....» .. .,
••*•! •! *• • t
. ., ? -
J
?» • I'M**
i - T ', * i 1,1,'
40 50 60 70 80 90
Adjusted Outdoor Day/Night Sound Level of Intruding Nois* in dS
FIG. 8-1. COMBINED DATA FROM COMMUNITY CASE STUDIES
ADJUSTED FOR CONDITIONS OF EXPOSURE
SOURCE: Ref. 5
Why is "percent highly annoyed" used as an index of community annoyance?
The use of the percentage of exposed persona who race themselves highly annoyed
is used because it is the most stable indicator of annoyance. Persons who
perceive their noise exposure as an extreme annoyance have littla difficulty in
sorting their feelings out from other non-acoustic variables which tend to
scatter responses on surveys which try to determine the median community
response. Because the highly annoyed individual exhibits a definitive response,
a clearer and more meaningful relationship between outdoor noise exposure and
annoyance can be seen through this index. (80) 3y looking at this index, one also
has an idea of the magnitude of the annoyance problem by looking at Che worst case.
Nevertheless, it should be recognized that many more poeple are annoyed, but to &
lesser extent, than would be indicated by the descriptor "bighly annoy»d".
8-3
-------
What, if any, distinction should be made between individual and collective
response?
It should be kept in mind that community response to noise is based on
statistical averages since it is known that response to noise varies greatly
among individuals.
Based on the Levels Document, what is the relationship between annoyance,
complaints, and community reaction as a function of day-night sound levels?
According to the EPA Levels Document, (5) approximately 17 percent of the
population will be highly annoyed at an L, of 55 dB, and over 40 percent of the
population will be highly annoyed ^£ the L, exceeds 70 dB, the maximum safe level
EPA has identified to protect against a risk of hearing loss. The lelationship
between noise and annoyance given in the Levels Document is based largely on the
results of surveys around airports. These estimates have been crticized because air-
craft noise is not present in many urban areas. CompU^C3 occur at a much lowej.
rate than annoyance, and generally do not become evident until the noise levels are
rather high. At an L, of 70 dB, approximately ten percent can be expected to
complain, while 25 to 40 percent of the population will be annoyed. At an L. of 55
dn
dS, complaints are expected to be almost non-existent. Vigorous community action
can be expected as the L, exceeds 70 dB.
an
What is the late1 t TJteria showing the extent of community annoyance thct can be
expected from givon levels of noise?
Schultz (30) synthesized results from nineteen social surveys of annoyance and
found a remarkable consistency. The synthesized data yields a somewhat different
result from that relationship depicted in the EPA Levels Document. Figure 3-2
from Shultz shows Che close clustering of annoyance curves from uany
transportation sources. Generally, data synthesized from prior social surveys
on noise as displayed in Figure 3-2 indicate Chat very few people (on average
8-4
-------
100 __
90 , —
qn ,
70
*
30
:o
10 ,
"CLUSTERING Sro'.TiS"
i
~- ~ Is: HEATHROW A/C (1961)
rS£N'a, A, C u966)
Mraira A/C (197:
PARIS STRICT (1969)
S'.TTISH A/'C (1972)
LONEOS STS^rr (197:)
. SVl^SS A/C (1973)
• LAX U973)
^
^
x^^"
^^
^^""
1
/
/
/
/ 1
/
A '
,///:?
•jlffr
y'/^-'i
''/
1 1 J 1 i 1 J
i 1
-° so so ;o so 50
L, (decibels)
an
FIG. 8-2. SUMMARY OF AXN'OYAN'CE DATA FROM 12 Sl'R'.T.'S
WITH DATA SHOWirG CLOSE AGR£i:-E>~.
SOURCE: Ref. 30
3-5
-------
three to four percent) will be highly annoyed by noise at or below a level of about
L =55 dB. However, about 16 percent of the population will be highly annoyed
dn
bv noise at about a level of L, =65 dB; twenty-five percent of the population
1 dn
will be highly annoyed at L = 70 dB; and thirty-seven percent of the population
will be highly annoyed as the noise level reaches Ldn = 75 dB. Twenty to thirty
percent of the population are apparently imperturbable and not bothered even
by high noise levels. (81) The Committee on Hearing, Bioacoustics, and
Biomechanics (CHABA) has indicated that these data are ap to date and has
included them in its guidelines for environmental impact statements on noise
(81).
Are there other measures which are considered good predictors of community
annoyance?
The Urban Noise Survey found that activity interference £of speech, sleep, etc.)
is a good predictor of annoyance. Speech interference is one of the most widely
perceived effects of environmental noise. Another predictor of community
annoyance is population density. Higher population density areas generally have
higher noise levels, thus the annoyance is greater. (82)
Vfhat other factors may influence personal reaction to noise?
Social surveys have shown that the following factors may contribute to community
noise annoyance;
1. Fear associated with activities of noise sources (such as fear of
crashes in the case of aircraft noise)
2. Socioeconomic status and education level
-------
4. Attitude of the community's residents regarding the contribution of
activities associated with the noise source to the general well-
being.
5. The extent to which residents of the community believe that the noise
source could be controlled (14)
RESULTS FROM THE URBAN" NOISE SURVEY
A total of 2037 people (726 men, 1275 women) were interviewed for this survey.
Twenty-four sites were selected to represent areas with different noise levels
and population densities. Sites where either aircraft noise or highway noise
predominated were excluded.
How does noise exposure relate to general neighborhood satisfaction?
Comparing responses from people in high noise exposure areas (mean L^ • 70 dB)
and low noise exposure areas (mean L, » 54.6 dB), it was found that 34 percent
fewer people in the high exposure areas described their neighborhood as an
excellent place to live, and 24 percent more people in these areas described
their neighborhood as only satisfactory. Seventeen percent more people in the
high exposure areas responded that they had been annoyed by noise. (82)
8-7
-------
What was the relationship between noise level and annoyance shown by the survey?
Noise Level (L. ) Percentage of Population Annoyed
_____ -an— w '
55 7
60 12
65 17
70 23
(82)
How does population density affect community response to noise?
High population density is usually associated with higher noise levels. It is
not surprising then that people in high density areas are more annoyed by noise
than people in low density areas. In the Urban Noise Survey, respondents living
in high density areas reported 20 percent more listening interferences, 9 percent
more conversation interferences, and 9 percent more sleep disturbances than
respondents in low density areas. (82)
Can socioeconomic status be related to annoyance from noise?
Generally, people in upper income brackets are less likaly to be annoyed by
noise because they can be more selective in deciding where to live. Since peace
and quiet are important selection factors, the wealthy are more likely to reside
in quiet neighborhoods and therefore can avoid annoyance from noise.
How does the time of day, season, location (indoors or outdoors) affect community
response to noise?
In relatively noisy areas where the L, exceeds 60 dB.people consider noise to be
more obtrusive in the evening and night hours. People are more annoyed by noise
in the summer, presumably because windows are open, and there may be additional
8-8
-------
noise sources such as air conditioners and lawnmowers . The results of the survey
also show that people are more annoyed by noise indoors than outdoors. (82)
What are some of the major conclusions drawn from this survey?
o Exposure to noise typical of many urban (non-aircraft and non-highway)
environments produces widespread annoyance, speech interference, and
sleep disturbance.
o A strong relationship was demonstrated between exposure level and the
proportion of a community highly annoyed by noise.
o The prevalence of speech interference is an especially good predictor
of annoyance.
o Population density is an important correlate of noise exposure.
o The number cf complaints about noise is a poor predictor of the
prevalence of annoyance.
o Demographic factors alone are relatively poor predictors of noise
annoyance.
o Freedom from noise exposure is a civta^onent of neighborhood
satisfaction, and quiet is highly valued.
8-9
-------
HEALTH AND WELFARE ANALYSIS
What methods are used to ascertain noise impact and predict the benefits of
implementing noise reduction measures?
A number of current state-of-the-art criteria of noise effects on people may be
employed Co gauge the impact of noise and the benefits to be gained by reducing
noise. Criteria in general use are those representing Lhe amount of annoyance to
be expected at different levels of noise, the potential for interference with
speech .communication and the probability of disturbed sleep due to noise. This
is not to say that other noise effects do not occur. There are indications of the
presence of many other effects of noise. However, cause-effect criteria have not
been derived for these other effects, and knowledge is generally insufficient for
health and welfare analysis purposes. Nevertheless, the criteria for general
adverse response (annoyance) may be used as a basis to infer these remaining
effects of noise on people. (8, 81) •
What is "Level-Weighted Population" and how is it used?
Level-Weighted Population (LWP) (81) expresses both the extent and the
severity of a r.oise impact. The extent of impact refers to the number of people
who are adversely affected, while the severity represents the degree to which
each person is affected. LWP provides a simple, single number used to compare
benefits of different noise reduction options.
It has been determined that an outdoor L, value of 55 dB (or an indoor L of 45
dn dn
dB) represents the lower threshold of noise jeopardizing the health and welfare
of people. In the range abovp these levels, noise may be a cause of adverse
physiological and psychological effects. These effects often result in annoyance
and community action. Noise ab_qye ^ ?5 dB may^ ln tim&f cause hearinK logg
and the possibility of other severe health effects.
References are listed in Section li, e.g.: (Ref. 8).
9-1
-------
The computation of L.WF allows one to combine the number of people jeopardized by
noise above an L^n of 55 dB with the degree of impact at different noise levels.
Figure 9-1 is a pictorial representation of the LWP concept. The circle is a
noise source which emits noise to a populated area represented by the figures.
The various partial amounts of shading represent various degrees of partial
impact by the noise. Note that those people closest to the noise source are more
severely threatened. The partial impacts are then sucnmed to give the equivalent
noise impact. In this example, six people who are adversely affected by the
noise (partially shaded) results in a Level-Weighted Population of two (totally
shaded).
FIG. 9-1. LEVEL WEIGHTED POPULATION: A METHOD TO
ACCOUNT FOR THE EXTENT AND SEVERITY OF
NOISE IMPACT.
9-2
-------
SUMMARY OF HUMAN EFFECTS FROM VARIOUS OUTDOOR
NOISE LEVELS
The following five tables present information on the possible effects on people
caused by outdoor day-night noise levels of 55, 60, 65, 70, and 75 decibels.
Summary of Human Effects for Outdoor Day-Night Sound Level of 55 Decibels
Type of Effect
Hearing Loss
R.'.sk of nonauditory disease
(stress)
Speech** - Indoors
- Outdoors
Magnitude of Effect
Will not occur
*
No disturbance of normal conversation. 100
percent sentence intelligibility (average)*with a
5 dB margin of safety
Slight disturbance of normal voice* or relaxed
conversation with 100 percent sentence
intelligibility (average) at 0.35 meter
High Annoyance
Overt Community Reaction
Attitudes Towards Area
99 percent sentence intelligibility (average) at
1.0 meter
or
95 percent sentence intelligibility (average) at
3.5 meters
Depending on attitude and other non-acoustical
factors, approximately 4 percent of the
population will be highly annoyed.
None expected; 7 dB below level of significant
"complaints and threats of legal action," but at
least 16 dB below "vigorous action" (attitudes
and other non-acoustical factors may modify this
effect)
Noiso considered no more important than various
oth^r environmental factors
* and ** See the notes on page 10-6.
10-1
-------
Summary of Hunan Effects for Outdoor Dav-Nisht Sound Level of 60 Decibels
Type of Effect
Hearing Loss
Risk of nonauditory health
effects (stress)
Speech** - Indoors
- Outdoors
Magnitude of Effect
Will not occur
No disturbance of normal conversation. 100
percent sentence intelligibility (average)
with no margin of safety
Moderate disturbance of normal voice or
relaxed conversation with 100 percent
sentence intelligibility ('average) at 0.2
meter
or
99 percent sentence
(average) at 0.6 neter
intelligibility
or
High Annoyance
Average Connsunity Reaction
Attitudes Towards Area
95 percent' sentence
(average) at 1 meters
intelligibility
Depending on attitude and other non-
acoustical factors, approximately 9 percent
of the population will be highly annoyed.
Slight to moderate; 2 dB below level of
significant "complaints and threats of legal
action," but at least 11 dB below "vigorous
action" (attitudes and other non-acoustical
factors may modify this effect)
Noise nay be considered an adverse aspect of
the community environment
* and ** See the notes on page 10-6.
10-2
-------
Summary of Human Effects for Outdoor Day-Night Sound Level of 65 Decibels
Type of Effect
Hearing Loss
Risk of nonauditory health
effects (stress)
Speech** - Indoors
- Outdoors
Magnitude of Effect
Will not occur
Slight disturbance of normal conversation 99
percent sentence intelligibility (average)
with a 4 dB margin of safety
Significant disturbance of normal voice or
relaxed conversation with 100 percent
sentence intelligibility (average) at 0.1
meter
or
99 percent sentence
(average) at 0.3 meter
intelligibility
High Annoyance
Average Community Reaction
Attitudes Towards Area
95 percent sentence
(average) at 1.2 meters
intelligibility
Depending on attitude, and other non-
acoustical factors, approximately 15
percent of the population will be highly
annoyed.
Significant; 3 dB above lev-si of significant
"complaints and threats of legal action,"
but at least 7 dB below "vigorous action"
(attitudes and other non-acoustical factors
may modify this effect)
Noise is one of the i portant adverse
aspects of the community environment
* and ** See the notes on page 10-6.
10-3
-------
Summary of Human Effects for Outdoor Dav-Night Sound Level of 70 Decibels
Type of Effect
Hearing Loss
Risk of nonauditory health
effects (stress)
Speech** - Indoors
- Outdoors
High Annoyance
Average Community Reaction
Attitudes Towards Area
Magnitude of Effect
Will not likelv occur
Slight disturbance of normal conversation
approximately 99 percent sentence
intelligibility (average)
Significant disturbance of normal voice or
relaxed conversation with 100 percent
sentence intelligibility (average) possible
only at distances less than .06 meter
or
99 percent sentence
(average) at 0.2 meter
intelligibility
or
95 percent sentence ' intelligibility
(average) at 0.6 meter
Depending on attitude and ocher non-
acoustical factors, approximarely 25
percent of the population will be highly
annoyed.
Severe; 8 dB above level of significant
"complaints and threats of lezal action,"
but at least 2 dB below "vigorous action"
(attitudes and other non-acoustical factors
may modify this effect)
Noise is one of the most important adverse
aspects of the community environment
* and '•** See the notes on page 10-6.
10-4
-------
Summary of Human Effects for Outdoor Day-Night Sound Level of 75 Decibels
Tvoe of Effect
Hearing Loss
Risk of nonauditory
health effects
(stress)
Speech** - Indoors
- Outdoors
Magnitude of effect
May begin to occur in sensitive individuals, depending
on actual noise levels received at-ear.
Some disturbance of normal conversation. Sentence
intelligibility (average) approximately 98 percent
Very significant disturbance of normal voice or relaxed
conversation with 100 percent sentence intelligibility
not possible at any distance
99 percent sentence intelligibility (average) at 0.1
meter
or
95 percent sentence intelligibility (average) at 0.4
meter
High Annoyance
Average Community
Reaction
Attitudes Towards
Area
Depending on attitude and other non-acoustical factors,
approximately 37 percent of the population will be
highly annoyed.
Very severe; 13 dB above level of significant
"complaints and threats of legal action" and at least 3
dB above "vigorous action" (attitudes and other non-
acoustical factors r?,ay modify this effect).
Noise is likely to be the most important of all adverse
aspects of the community environment.
* and ** See the notes on page 10-6.
10-5
-------
The following notes should be kept in mind when examining the preceding five
Cables:
* Research implicates noise as a factor producing stress-related health
effects such as heart disease, high blood pressure and stroke, ulcers and
other digestive disorders. The relationships between noise and these
effects have not yet been quantified, however.
** The speech effects data in these tables are drawn from the Levels Document
(5), as follows. Indoor effects are based on Table 3, and on Figure D-l,
with 15 dB added to the indoor level to obtain the outdoor reading. Outdoor
effects come from Figure D-2, using L. (as determined with Figure A-7).
Both Figures D-l and D-2 are based on steady noise, not on L . Table D-3
shows that for fluctuating noise the average percent interference is lower
than for steady noise of the same L . The values given in this report are
the best estimates of the interference.
NOTE; Outdoor speech intelligibility estimates assume 70 dD (67 dBA) level of
speech.
10-6
-------
REFERENCES
1. United States Public Law 92-574, "Noise Control Act of 1972," (October 27,
1972).
2. United States Public Law 95-609, "Quiet Communities Act of 1978," (January
19, 1973).
3. Bachmann, W., "Health and Disease. Critical Fnoughts on the Health Concept
of che World Health Organization," Munchen Med. Wochenschr, Vol. 119, (May
18, 1977), p. 349.
4. U.S. Environmental Protection Agency, "The Status of Noise Control in The
United States: State and Local Governments," (prepared by Dr. Clifford R.
Bngdon, Dept. of City Planning, Georgia Institute of Technology), (April
1978),
5. U.S. Environmental Protection Agency, "Information on Levels of Environ-
mental Noisi Requisite to Protect Public Health and Welfare with an Adequate
Margin of Safety," 550/9-74-004, (March 1974).
6. U.S. Environmental Protection Agency, "Protective Noise Levels (condensed
version of EPA Levels Document)," 550/9-79-100, (November 1978).
7. U.S. Environnental Prott tion Agency, Office of Noise Abatement and Con-
trol, Noise in America, Washington, D.C., in preparation.
6. Schori, T. R. , "A Real World Assessment of Noise Exposure," EPA-AI-31L Report
TR-77-96, (August 1978).
9. U.S. Environmental Protection Agency, Toward a National Strategy for N'oise
Control. (Apri! 1977).
10. Federal Register, Vol. 42, No. 23, (February 3, 19771, pp. 6722-6723.
11. U.S. Environmental Protection Agency, "Effects of Noise on People," NTID
300.7, NTIS Document No. PB-206723, (December 1971).
12. Davis, H., and Gilvenian, S. R. , Hearing and Deafness, New York: Holt,
Rin«?h2rt, and Ninston, (1966).
13. Newby, H.A., Audiology. Enjiewood Cliffs, M^w Jersev: Prentice Hall, Inc.,
(1972).
14. U.S. Environmental Protection Agency, Public Health and WeUare Criteria
for Nois.e, 550/4-73-002, (July 27. il-73).
11-1
-------
15. Royster, L. H. , "Potential Hearing Compensation Cost, Percent of the
Population Exceeding Different Frequency Low Fence Hearing Threshold Level
Combinations and Equivalent Frequency Low Fence Combinations for Black and
White, Male and Female Population," paper presented befora the Acoustical
Society of America, (May 1978).
16. Martin, F., Introduction to Audiolo|y, Englewood Cliffs, New Jersey:
Prentice Hall Inc., (1975).
17. Taylor, W., et al., "Study of Noise and Hearing in Jute Weaving," Journal of
the Acoustical Society of America, Vol. 38.
18. Henderson, D., ed., et al., Effects of Noise on Hearing, New York: Raven
Press, (1976).
19. Schein, J. D., and Deck, M. T., The Deaf Population of the United States,
published by the National Association of the Deaf in cooperation with
Deafness Research and Training Center, New York University, (1974).
20. Kryter, K., The Effects of Noise on Man, New York: Academic Press, (1971).
21. Hamernik, R. P., et al., "Impulse Noise and Synergistic Effects Aggravate
Hearing Loss," Journal of Occupational Safety and Health, (January/February
1978), pp. 21-27.
22. Hodge, D. C., and Price, G. R., "Hearing Damage Risk Criteria," Noise and
Audiology, ed. D. M. Lipscomb, Baltimore: University Park Press, (1978),
pp. 167-191. *
23. Cuniff, P. F., Environmental Noise Pollution, New York: John Wiley and
Sons, (1977).
24. Ward, W. D., et al., "Temporary Threshold Shift Produced by Intermittent
Exposure to Noise," Journal of the Acoustical Society of America, Vol. 31,
No. 6, (1959), pp. 791-799.
25. Federal Register, Vo. 36, No. 105, (May 21, 1971), p. 10158.
26. Spoor, A., "Presbycusis Values in Relation to Noise-Induced Hearing Loss,"
International Audiology, Vol. 6, No. 1, (July 1967), pp. 48-57.
27. Cohen, A., Anticaglia, J., and Jones, H. H., "'Sociocusis' - Hearing Loss
From Non-Occupational Noise Exposure," Sound and Vibration, (November
1970), pp. 12-20.
28. Rosen, S., "Presbycusii; Study of a Relatively Noise-Free Population in the
Sudan," Annals of Otology. Rhinology, and Laryngology, (1967), pp. 727-743.
11-2
-------
29. Rintleman, W., and Bienvenue, G., "Rock Music and Noise-Induced Hearing
Loss: A Review of Research," presented during A Symposium on Rock Music and
Noise-Induced Hearing Loss at Che 55th Audio Engineering Society Con-
vention, (October 29 - November 1, 1976).
30. Whittle, L. S., and Robinson, D. W., "Discoteqae and Pop Music as a Source
of Noise-Induced Hearing Loss, a Review and Bibliogrpahy," National
Physical Laboratory, NPL Acoustics Report AC66, (March 1974).
31. Miller, J. P., "The Effect of Noise on People," Journal of tha Acoustical
Society of America, Vol. 56, No. 3. (September 1, 1974), pp. 729-764.
32. Mills, J. H., "Noise and Children - A Review of Literature," Journal of the
Acoustical Society of America, Vol. 58, No. 4., (October 1975), pp 767-779.
33. Cohen, A., "Effects of Noise on Psychological State", ASHA Proceedings,
(1969), pp. 74-88.
34. Suter, A., and Von Gierke, H. E., "Evaluation and Compensation of
Occupational Hearing Loss in the United States," presented at the Conference
of the World Health Organization, Turin, Italy, (June 9, 1975).
35. American Academy of Ophthalmology and Otolaryngology, Committee on Conser-
vation of Hearing, "Guide for the Classification and Evaluation of Hearing
Handicap," Trans. American Academy of Ophthalmology Otolaryngology, 69,
(1965), pp. 740-751. )
36. AAOO, "Guide for Evaluation of Hearing Handicap," Journal of the American
Medical Association, Vol. 41, No. 19, (1979), pp. 2055-2059.
37. "Criteria for a Recommended Standard Occupational Exposure to Noise,"
Department of Health, Education and Welfare, National Institute of
Occupational Safety and Health, HSM 73-11001, (1972).
38. Ginnold, R., "Occupational Hearing Loss: Workers Compensation in State and
Federal Programs," EPA 530/9-79-101, (1979).
39. U.S. Department of Housing and Urban Development, "Annual Housing Survey:
1975, Part B, Indicators of Housing and Neighborhood Quality," Series H-150-
753, (1977).
40. Ando, Y., and Hattori, H., "Statistical Studies on the Effects of Intense
Noise During Human Fetal Life," Journal of Sound and Vibration, (1973), pp.
101-110.
41. Selye, H., The Stress of Life, New York: McGraw Kill Book Co., (1956).
42. Peterson, EC A., e£ al., "Noise and Cardiovascular Function in Rhesus
Monkeys," Journal of Auditory Research, No. 15, (1975), pp. 234-251.
11-3
-------
43. Jonsson, A., and Hansson, L., "Prolonged Exposure to a Stressful Stimulus as
a Cause of Raised Blood Pressure in Man,"'The lancet. (January 1977), pp.
86-37.
4«, Frerichs, R. R. , Beeman, 3. L. , Coulson. A. H. "Los Angeles Airport. N'oise
and Mortality Faulty Analysis and Public Policy," Anericsn Journal of
Public Health, Vol. 70, No. 4, (April 1980) pp. 357-361.
45. Geber, W., "Cardiovascular and Teratogenic Effects of Chronic Intermittent
Noise Stress," ed. Welch, 3. L. and Welch, A. S. , Physiological Effects of
Noise, (1970), pp. £5-90.
45. Edoonds. I... Layde, P. M. , and Erikson J. ?., "Airport Noise and
Teratogenesis," Archives of Environental Health, (July-August 197S) pp.
243-247.
47. Tobias, J. V., and Irons, F. X,, "Reception of Distorted Speech," in
Proceedings of the International Congress on Noise as a Public Health
Problem. Dubrovnik, Yugoslavia, May 13-13, 1973. Washington, ?.C.: U.S.
Environmental Protection Agency, 550/9-73-008, (1973), pp. 43-56.
48. Suter, A. H., "The Ability of Mildly Hearing-Impaired Individuals to
Discriminate Speech in Noise," Washington, D.C.: U.S. Environmental
Protection Agency and Wright-Patterson Air Foice Base, Ohio: Aerospace
Medical Research Laboratory, (January 1973).
49. Durrant, J. D., "Anatomic and Physiologic Correlates of the Effects of Noise
on Hearing," in Noise and Audiology. ed. D. M. Lipscomb, Baltimore:
University Park Press, (197S), pp. 109-141.
50. Webstar, J. C., "The Effects of Noise on the Hearing of Speech," in
Proceedings of the International Congress on Noise as a Public Health
Problea. Dubrovnik, Yugoslavia. May 13-iS, 1973. Washington. D.C.: U.S.
Environmental Protection Agency, 550/9-73-003, (.1973), pp. 25-^2.
51. Carpenter, A., "Effects of Noise on Performance and Productivity," in
Control of Noise. Symposium No. 12, (Her Majesty's Stationery Office.
London, 1962) .
52. Harris, C. S. , "The Effects of Different Types of Acoustic Stimulation :~
Performance," in Proceedings of the International Congress en Noise as a
Public Health Problea. Dubrovnik. Yugoslavia, vMay 13-18, 1973).
Washington, D.C.: U.S. Environmental Protection Agency. (1973) 550/9-73-
OOS, pp. 389-407.
53. Guliaa, E., "Noise as an Occupational Hazard: Effects on Performance Level
and Health - A Survev of bindings in the European Literature," (May 20.
1974).
54. Sroadbent, D . E., "Effects of Noises of High and Lev Frequency in Behavior."
Ergonomics. Vol. 9-10, (1957), pp. 21-29.
11-4
-------
55. Boggs, D. H., and Simon, J. R., "Differential Effects of Noise on Tasks of
Varying Complexity," Journal of Applied Psychology, Vol. 52, (1968), pp 148-
153.
56. Glass, 0. C., and Singer, J. E., Urban Stress Experiments on Noise and
Social Stressors, New York: Academic Press, (1972).
57. Wilkinson, R. T., "Some Factors Influencing the Effects of Environmental
Stressors Upon Performance," Psychological Bulletin, Vol. 72, (1969), pp
260-272.
58. Blake, M. J. F., "Temperamenc and Time of Day," in Biological Rhythms and
Human Performance, W. P. Colquhoun (ed.), London: Academic Press, (1971),
pp. 109-148.
59. Davies, D. R., and Hockey, G. R. J., "The Effects of Noise and Doubling the
Signal Frequency on Individual Differences in Visual Vigilance
Performance," British Journal of Psychology, Vol. 57, (1966), pp. 381-389.
60. Discipio, W. J., "Psychomotor Performance as a Function of White Noise and
Personality Variables," Perceptual and Motor Skills, Vol. 33, (1971), p. 82.
61. Broadbent, D. F., Decision and Stress, London: Academic Press, (1971).
62. Kahneman, D., Attention and Effort, Englewood Cliffs, New Jersey: Prentice
Hall, (1973).
63. "Industrial Noise and Worker Medical, Attendance and Accident Records,"
U.S. Department of Health, Education, and Welfare, Public Health Service,
and the National Institute for Occupational Safety and Health, (June 1972).
64. U.S. Environmental Protection Agency, Office of Noise Abatement and
Control, "Some Considerations in Choosing an Occupational Noise Exposure
Regulation," (February 1976).
65. Bronzaft, A., _McCarthy, D., "The Effect of Elevated Train Noise on Reading
Ability," Environment and Behavior, Vol. 7, No. 4, (December 1975), pp.
517-527.
66. Cohen, S., Glass, D., and Singer, J., "Apartment Noise, Auditory
Discrimination, and Reading Ability in Children," Journal of Experimental
Social Psychology, Vol. 9, (1973), pp. 407-^22.
67. Griefahn, B., and Muzet, A., "Noise-Induced Slesp Disturbances and Thair
Effects on Health," Institut Feur Arbeits -und Sozialmedizin, Universitaet
Mainz, West Germany and Centre d'Etudes Bioclimatiques du CNRS, France,
68. Lukas, J. S., "Measures of Noise Level: Their Relative Accuracy in
Predicting Objective and Subjective Responses to Noise During Sleep,"
Washington, D.C.: U.S. Environmental Protection Agency, 600/1-77-010,
(February 1977).
11-5
-------
69. Lukas, J. S., Dobbs, M. E. , "Effects of Aircraft Noise en the Sleep of
Women," National Aeronautics and Space Admiaistration, Report No. CR 2041.
70. Dobbs, M. E., "Behavioral Responses to Auditory SLirav.lation During Sleep,"
Journal of Sound and Vibration-, Vol. 20, (1972), pp. 467-476.
71. Williams, H. L. and Williams, C. L., "Nocturral EEC Profiles and
Performance," Psychophysiol, Vol. 3, (1966), pp. 16-+-175.
72. Grandjean, E. et al., "A Survey on Aircraft Moise in Switzerland," in
Proceeding of the International Congress on Noise as a Public Health
Problem, 550/973-008, (1973), pp. 615-660.
73. Scharf, B., et al., U.S. Environmental Protection Agency, "Comparison of
Various Methods for Predicting the Loudness and Acceptability of Noise,"
550/9-77-101, (August 1977).
74. National Academy of Science - National Regulatory Ccmmissian, Committee on
Hearing, Bioacoustics, and Biomechanics, "Proposed Dama§^ - Risk Criterion
for Impulse Noise (gun fire)." Report of Working Group 57, Washington, D .C.
(1968).
75. McLean, E. K., and Tarnopolsky, .-». , "Noise, Discomfort, and Mental Health,"
Psychological Medicine, (Augusr 1977), pp. 19-51.
76. Borksy, P., "Review of Community Response to Noise," contained in
proceedings of 3rd International Congress on Noise as a Public Health
Hazard, American Speech Language Hearing Assoc., Report 10, (1980), pp.
452-474.
77. Matthews, X. E., and Canr.on, L. K., "Environmental Noise Level as a
Determinant of Helping Behavior," Journal of Personality and Social
Psychology, (1975), pp. 571-577.
78. Sherrod, D. R. , and Downs, R. , "Env' ronmental Detatainanta of Altruism: the
Effect of Stimulus Overload and Perceived Centre; on Helping," Journal of
Experimental Social Psychology, Vol. 10, (1974), pp. 468-479.
79. Geen, R. G., and Powers, P. C., "Shock and Noise as Instigating Stimuli in
Human Aggression," Psychological Reports, Vol. 28, (1971), pp. 983-985.
80. Schultz, T. J., "Synthesis of Social Surveys on Noise Annoyance," Journal of
the Acoustical Society of America, Vol. 64, No. 2, (August 1973), pp. 377-
405.
81. Committee on Hearing, Bioacoustics, and Biomechanics, "Guidelines for
Preparing Environmental Impact Statements on Noise," Report of Working
Group No. 69, National Academy of Sciences, (1977).
82. U.S. Environmental Protection Agency, "The Urban Noise Survey," 550/9-77-
100, (April 1977).
11-6
-------
83. Goldstein, J., "Assessing Che Impact of Transportation Noises Human
Response Measures," in Proceedings of the 1977 National Conference on Noise
Control Engineering, (ed.), G. C. Haling,, NASA Langley Research Center,
Hampton, Virginia, (October 1977), pp. 79-98.
84. U.S. Department of Health, Educaf.ion and Welfare, l:Fifth Report of the
Director of the National Heart, Lung, and Blood Institute," DHEW Publication
No. NIH-78-1415, (February 1978).
85. Jones, F. N., and Tauscher, J., "Residence Under an Airport Landing Pattern
as a factor in Teratism," Archives of Environmental Health, (January-
February 1978), pp. 10-11.
86. Cohen, Alexander, "Industrial Noise and Medical, Absence, and Accident
Record Data on Exposed Workers," in Proceedings of the International
Congress on Noise as a Public Health Problem, Dubrovnik, Yugoslavia, May 13-
18, 1973, Washington, D.C.: U.S. Environmental Protection Agency, 550/9-
73-008, (1973), pp. 441-453.
87. Webster,- J. C., "Effects of Noise on Speech Intelligibility," in Pro-
ceedings of the Conference on Noise As a Public Health Hazard, (1969), pp.
49-73.
88. Lukas, J. "Noise and Sleep: A Literature Review and a Proposed Criteria
for Assessing Effect," in Handbook of Noise Assessment, ed. Darly N. May,
Van Nostrand Reinhold Company:New York, (1978), pp. 31?-334.
89. Thiessen, G. J., "Effects of Noise from Passing Trucks on Sleep," Report
Ql, presented at 77th meeting of the Acoustical Society of America,
Philadelphia, (April 1969).
90. Abey-Wickrania, I., a'Brook, M. F,, Gattoni, F. E. G., & Herridge, C. F.
"Mental Hospital Admissions and Aircraft Noise," Lancet, (1969), pp. 1275-
1277.
91. ANSI, American National Standards Institute, "Methods for the Calculation
of the Articulation Index" ANSI S3.5-1969.
92. ANSI, American National Standards Institute, "Rating Noise with Respect to
Speech Interference" ANSI S3.14-1977.
93. Horonjeff, R. D., and Teffeteller, S. R., "Sleep Interference from
Intermittent and Continuous Noise Exposure," presented at the 98th Meeting
of the Acoustical Society of America, Salt Lake City, Utah (November 27,
1969).
94. Horonjeff, R. D., et al., "Sleep Interference from 'Low Level Sounds",
presented at the 96th Meeting of the Acoustical Society of America,
Honolulu, Hawaii (November 30, 1978).
95. Royster, L. H., J. D. Royster, and W. G. Thomas, "Representative Hearing
Levels by Race and Sex in North Carolina Industry", Journal of the
Acoustical Society of America. Vol. 68, No. 2, (August 1980).
11-7
-------
96. Cohen, S., Krintz, D. S. , Evans, G. W. and D. Stokols. "Community Noi?e and
Children: Cognitive Motivational and Physiological Effects." In Tobias, J.
V., Jansen, G., and Ward, W. D. (Eds.). Proceedings of the Third
International Congress on Noise as a Public Health Problem, ASHA Report 10,
(April 1980).
97. Meecham, W. C., Shaw, N. "Effects of Jet Noise on Mortality Rates," British
Journal of Audiology, Vol. 13, (1979), pp. 77-80.
98. Kryter, K. D., Pazo, F. "Effects of Noise on Some Auccnomic System
Activities," Journal ot the Acoustical Scoiety of America, Vol. 67, (1980),
pp. 2036-2044.
99. Dept. of Labor, OSHA. "Occupational Noise Exposure; Hearing Conservation
Amendment," Jan. 16, 1981.
100. Welch, B. L. Extra-auditory Health Effects of Industrial Noise: Survey of
Foreign Liteature, June 1979.
101. Knipschild, P. "Medical Effects of Aircraft Noise: Drug Survey" Int.
Arch. Occup. Envir. Health. Vol. 40 (1977).
102. Cantrell, R. W. "Prolonged Exposure to Intermittent Noise: Audiometric,
Biochemical, Motor, Psychological, a-.id Sleep Effects" Laryngoscope
Supplement I Vol. 84, No. 10, pt. 2, (Oct. 1974).
103. Ising, M. et al. "Study on the Quantification of Risk for the Heart and
Circulatory System Associated with Noise Workers." Institute for Water and
Air Hygiene of the BGA, Berlin (1979).
104. Karsdorf, G. and Klappach, H. "The Influence of Traffic Noise on the Health
and Performance of Secondary School Students in a Large City.1' Zeitschrift
fur die Gesamta Hygiene, (1968).
105. Manninen, 0. and Aro S. "Noise-induced Hearing Loss and Blood i'ressure.
Int'l Archives of Occup. and Envir. Health, Vol. 42, (1979).
106. Peterson, E. et al. "Noise Raises Blood Pressure Without Impairing Auditory
Sensitivity" Science, Vol. 211, No. 4489, (Mar 27, 1981).
11-8
-------
INDEX
AAOO (American Academy of Ophthalmology and Otolaryngology)
Hearing impairment compensation formula, 2-30
ABC Network
Harris survey, 1-2
AMA (American Medical Association)
Hearing impairment compensation formula, 2-31
Absenteeism—see Workplace
Accidents—see Safety
Acoustic Reflex
Defined, 2-10
Adrenalin
Part of stress syndrome, 3-1
Aftereffects
On performance, 5-2, 5-4
Age
Hearing differences, 2-4
Effect on hearing loss, 2-15 to 2-16
Air Conduction
Testing, 2-4, 2-6
Aircraft Noise
As souice of neighborhood dissatisfaction, 1-1
Population exposed to, 1-1 to 1-4
Relation to cardiovascular problems, 3-4
Possible fetal effects, 3-9
Relation to mental illness, 7-1
Relation to mortality rates, 3-9
12-1
-------
Airport Noise—see Aircraft Noise
Annoyance
Neighborhood dissatisfaction, 1-1, 8-1
Population annoyed, 1-1 to 1-2
Population severely annoyed, 1-2
As a function of Ldn, 10-
Survey results, 8-1, 8-4 to 8-7
Effects of noise quality, 7-4
Means, 8-1
Predictors, 8-2, 8-4 to 8-6
Relation to socioeconomic status, 8-8
As psychological response, 7-4
From sleep disturbance, 6-1, 6-7
Schultz curve, 8-5
Special populations, 7-4
As index of community reaction, 8-3
Annual Housing Survey
Findings, 1-1, 8-1
Antisocial Behavior
As stress effect, 7-5
Arousal Response—see also Startle Reflex
Defined, 3-1
Articulation index—see Communication Interferer.ee
Attitudes—see also Annual Housing Survey
Urban Noise
As a function of L. , 10-1 to 10-6
an
Audiogram—see also Hearing, Measurement
Sample, 2-5
OSHA requirements, 2-27 to 2-28
Types of uses, 2-29
Audiometry—see Audiogram
Hearing Measurements
Auricle—see Ear Function
12-2
-------
Automobile Noise—see Traffic Noise
Autonomic Nervous System
In physiological response, 5-2
Awakening—see Sleep Disturbance
Babies—see Fetus
Balance—see Vertigo
Benefits—see also Compensation
Of regulations, 9-1 to 9-2
Birth Defects
Possible link with noise, 3-1, 3-10
Effect en hearing, 2-6
Birth Weights
Low birth weights, 3-1, 3-S
Budgets—see Costs
Blood Pressure
Arousal response, 3-1
Vasoconstriction, 3-2
Hypertension, 3-1 to 3-6
In laboratory animals, 3-5
Pressure changes as stress effect, 3-4
Bone Conduction
Thresholds, 2-4
Testing, 2-6
CHABA
Guidelines, 2-14, 8-6
Cardiovascular Disease
As stress effect, 3-1
Relationship to noise, 3-3 to 3-5
12-3
-------
Car Noise—see Traffic Noise
Census Bureau—see Annual Housing Survey
Center for Disease Control
Fetal birth weight studies, 3-10
Children
With hearing loss, 2-8
Effects during sleep, 6-6
Physiological stress effects on, 3-5
Performance interference, 5-5
Cholesterol
Relation r.o noise, 3-3
City Noise—see Urban Noise
i
Cleft Palates—s°e Birth Defects
Cochlea—see Ear Function
Colitis—see also Digestive Disorders
As stress effect, 3-1, 3-7
Conmunication Interference
In general, Chapter 4
As a function of Ldn, 10-1
Resulting from hearing loss, 2-19 to 2-20
Indirct effects, 4-1
Effects on social interaction, 4-1
Effects on safety, 4-1
Effect of speech quality, 4-2
Factors of extent, 4-2
Criteria, 4-4 to 4-6
Articulation index, 4-3
Effects of temporal quality, 4-2 to 4-3
Speech interference level, 4-3
Best weighting scale, 4-3
Protective levels, 4-4
Intelligibility, 4-3
Relating to community response, 8-1
Effects on children, 4-8 to 4-9
12-4
-------
Communication Interference (Continued)
Effect of age, 4-8
From hearing loss, 4-8
Community Response
In general, Chapter 8
As a function of Ldn, 10-1 to 10-6, 9-4
Relating to activity interfernece, 8-1, 8-7
Neighborhood dissatisfaction, 1-1, 8-1, 8-9
Number of people at various exposure levels, 1-2 to 1-4
Opposed to individual response, 8-4
Synthesized data, 8-4 to 8-6
Relation to complaints, 8-4, 8-8
Comparison of Levels Document and prior survey data, 8-4 to 8-6
Relation to population density, 8-8 to 8-9
Relation to contextual factors, 8-8 to 8-9
Index of annoyance, 8-3
Socioeconomic factors, 8-8
How measured, 8-2
Criteria, 8-4 to 8-6
Compensation
Hearing impairment formulas, 2-30 to 2-31
State policies, 2-29 to 2-31
Why paid, 2-29
Use of audiograms, 2-29
Legal terms, 2-30
Compensation Formulas—see NIOSH
Complaints—see also Community Response
At various noise levels, 8-3 to 8-6
Predictive value, 8-2
Conductive Hearing Loss
Defined, 2-5
How determined, 2-6
Causes, 2-5
Congenital Problems—see Birth Defeccs
Fetus
Contextual Factors—see also Psychologicr.l Response
Relation to community reaction, 8-8
12-5
-------
Controllability
Effect on response, 5-2
Coping Behavior
From excessive exposure, 7-5
Coronary Disease—see Cardiovascular Disease
Cortisol
Increases in levels associated with noise, 3-6
Costs
Of cardiovascular disease, 3-4
Of work disruption, 5-5
Criteria
For nonauditory effects, 3-3
Hearing loss, 2-21
Speech interference, 4-4 to 4-6
Sleep disruption, 6-3 to 6-4
Steady state noise, 2-24
For impulse noise, 2-14
Summary tables, as a function of Ldn, 10-1 to 10-5
Daily Noise Exposure
Hypothetical, 1-5 to 1-6
Digestive Disorders—see also specific type
From noise-induced stress, 3-1 to 3-2, 3-7
Disability
Defined for compensation, 2-30
Drugs—see Toxic Substances
Ear Function
Description, 2-1 to 2-2
Testing, 2-4 to 2-6
Disruptive diseases, 2-6 to 2-7
Organ of Corti, 2-13
12-6
-------
EEC Changes
Noise-related, 6-2
Elderly
With hearing loss, 2-8
Effects during sleep, 6-6
Presbycusis, 2-15 to 2-16
Endocrine Disorders
As stress pffect, 3-7
Education—see Learning
Equal Energy Hypothesis
Defined, 2-13
Accuracy, 2-22
Equal Loudness Contour
Displayed, 7-4
£qual Temporary Effect Hypothesis
Defined, 2-12
Equivalent Noise Impact (ENI)—Level-Weighted Population (LWP)
Exposure (to Noise)—see also Residential Exposure
Occupational Noise
Urban Noise
Long-term nonauditory effects, 3-3
Short-term nonauditory effects, 3-2
Fatigue
As stress effect, 3-7, 7-1
From high-intensity noise, 5-2
From sleep disruption, 6-1
Fetus
Hearing damage, 2-6
Physiological effects, 3-1, 3-8
'Flight or Flight Syndrome"—see Arousal Response
12-7
-------
Gallup Poll
Results, 1-2
Gastrointestinal Problems—see Digestive Disorders
Harris Survey
Results, 1-2
Handicap
Defined for compensation, 2-30
Headaches
Noise related, 3-7
Hearing Conservation—see also Hearing Loss
Hearing protectors
Audiograms
Methods, 2-24 to 2-28
Hearing Loss—see also hearing Loss, Types
In general, Chapter 2
Population at risk, 1-5
Measurement of, 2-6
Relation to exposure, 2-9
Physiological basis, 2-11
Effects, 2-17 to 2-20
Compensation formulas, 2-30 to 2-31
Causes, 2-6 to 2-7
Susceptibility, 2-9, 2-11
From rock music, 2-18
Protective levels, 2-21
Protective emasures, 2-24 to 2-28
Due to aging, 2-16
Compensation, 2-29 to 2-31
Hearing Loss Claims—see Compensation
Hearing Loss, Types—see specific type:
Conductive
Sensori-neui'*!
Presbycusis
Sociocusis
Hearing Mechanism—see Ear Function
12-8
-------
Hearing, Measurement—see also Audiogram
Method, 2-4, 2-29
Of hearing loss, 2-6
Hearing, Normal
Based on sex, 2-3
Based on race, 2-4
Based on age, 2-4
Range, 2-1
Hearing Protectors
Types, 2-27 to 2-28
Attenuation characteristics, 2-28
Hearing Tests—-see Hearing, heasurement
Heart Problems—see Cardiovascular Disease
Helping Behavior
Effects from excessive exposure, 7-5
High Frequency Noise
Effects on performance, 5-2
Effects on subjective response, 7-4
Household Noise
Typical exposure, 1-5
HUD
Annual Housing Surveys, 1-1
Hypertension
As a stress effect, 3-1 to 3-6
Monkeys, 3-4
Hypotension
As a stress effect, 3-7
Immunological Resistance
Reduction from stress, 3-1
12-9
-------
Impairment
Defined for compensation, 2-30
Impedar.ce
Friction, 2-2
Impulse Noise
Effects, 2-13
Effect on speech interference, 4-2
Criteria, 2-14
Individual Response—see Psychological Response
Indoor Noise
Compared to outdoor levels, 1-6
Criteria, 4-4 to 4-5
Industrial Noise—see Occupational Noise
Infants—see Fetus
Information Content
Effect on sleep disturbance, 6-5
Effect on work performance, 5-3
Information Gathering—see Learning
Communeiation Interference
Performance Interference
Insomia
Noise related, 3-3
Interior Noise
Relation to outdoor noise, 1-2
Intensity—see also Loudness
Relation to subjective response, 7-2
Intermittency
Effect on performance, 5-2
12-10
-------
Intermittency (Continued)
Effect on speech interference, 4-2
Effect on subjective response, 7-2
Correction factor, 2-22
Irritability
As stress effect, 2-5, 7-1
In noisy work environments, 5-5
Kryter, Karl
Studies, 3-8
Learning
Effects from speech interference, 4-8 to 4-9
Disruption, 5-3, 5-5
Legislation—see Walsh-Healey Public Contracts Act
OSHA
Levels—see Recommended Levels
Level-Weighted Population
Defined, 9-1 to 9-2
Loudnsss
Effect on performance, 5-2
Effect on sleep, 6-2 to 6-6
Effect on threshold shift, 2-9
Of rock music, 2-18
Effect on subjective response, 7-2, 7-4
Effect from recruitment, 2-19
Effect on communication, 4-1
Masking—see Communication Interference
Mental Effects—see Psychological Effects
Physhological Response
Mecham, W.C.
Studies
Mental Illness
Relation to excessive noise, 7-1
12-11
-------
Metabolic Disorders—see Physiolgoical Effects
Migraines—see Headaches
Modifications—see Strategies, Control
Monkeys
Blood pressure study, 3-5
Mortality Rates
Effects from noise, 3-9
NIOSH (National Institute of Occupational Safety and Health)
Hearing impairment compensation formulas, 2-31
Hearing loss formula, 2-31
National Health Examination Survey
Of tinnitus, 2-20
National Institute of Occupational Safety and Health—see NIOSH
National League of Cities
Gallup poll, 1-2
National Noise Problem
In general, Chapter 1
People exposed, 1-1 to 1-5
Typical exposures, 1-5 to 1-6
Workers, exposed, 1-4
Nausea
From high-intensity noise, 5-2
Neighborhoods—see also Annoyance
Urban Noise
Annual Housing Survey
Community response surveys, 1-1 to 1-2, 8-1 to 8-9
Dissatisfaction, 9-1
Satisfaction as a function of L. , 10-1 to 10-6
12-12
-------
Neuroticism
As stress effect, 3-5
Newborn—see Fetus
Nonauditory Effects—see also Physiological Effects
Stress
In general, Chapter 3
Physiological changes, 3-1
Vasoconstriction, 3-2
From short-term exposure, 3-2
From long-term exposure, 3-3
Criteria, 3-3
Cardiovascular problems, 3-1, 3-3 to 3-7
Blood pressure^ 3-1, 3-3 to 3-6
Stress effects, 3-4 to 3.-6
Toxic substances, 3-1, 3-8
Fetus, 3-1, 3-10
During sleep, 6-2
On workers, 3-7
Differences in scientific opinion, 3-8
OSHA
Requirements, 2-14, 2-27 to 2-28
Occupational Safety and Health Administration—see OSHA
Occupational Noise
Compensation for hearing impariment, 2-29 to 2-31
Number of workers at risk, 1-5
Regulations, 2-14, 2-24
OSHA requirements, 2-27 to 2-28
Protective levels, 2-14, 2-21, 2-26
Impulsive noise, 2-14
Performance effects, 5-5
Societal costs, 5-5
Old People—see Elderly
Ossicular Chain—see Ear Function
12-13
-------
Ototocix Drugs—see Toxic Substances
Performance Interference
In general, Chapter 5
Exposure factors, 5-1
Exposure effects, 5-1 to 5-5
Detrimental levels, 5-2
Detrimental noise qualities, 5-2 to 5-3
Cumulative effects, 5-4
From industrial noise, 5-5
Aftereffects, 5-2Performance Interference (Continued)
Societal costs, 5-5
Fatigue from noise related stress, 5-5, 7-1
Affected tasks, 5-3
Individual variables, 5-3
Of learning, 5-3
Positive effects, 5-1, 5-4
After effects, 5-4
On children, 5-4
Personal Factors
In subjective response, 7-2, 7-5
In community response, 8-8
Peterson, Ernest
Blood pressure, 3-5
Phon
Defined, 7-3
Physiological Effects—see also Nonauditory Effects
Arousal response, 3-1
Of high-intensity noise, 5-2
During sleep, 6-1 to 6-2
Autonomic nervous system, 3-2
Population Density
As predictor of annoyance, 8-8 to 8-9
Predictability
Effect on performance, 5-2
Pregnant Women—see Fetus
12-14
-------
Presbycusis
Defined, 2-15
Progression, 2-15 to 2-16
Primates—see Monkeys
Psychological Effects
From industrial noise, 5-2
From high levels of noise, 7-1
Psychological Response
In general, Chapter 2
To high-intensity noise, 5-2
To excessive noise, 7-1
Subjective response to noise quality, 7-2
Contextual factors, 7-2
Personal factors, 7--2
Best weighting scale, 7-2
Annoying noises, 7-4
Of special populations, 7-4
Role of personality, 7-2
Coping behavior, 7-5
Antisocial behavior, 7-5
Use of sones, 7-3
Use of phons, 7-3
Public Health Survey
On hearing loss, 2-7 to 2-8
Public Opinion—see Annual Housing Survey
Community Response
Surveys
Urban Noise
Race
Hearing differences, 2-4
Rapid Eye Movement (REM)
Disruption, 6-6
Recommended Levels
Levels Document identified levels, 2-21
Validity of basis, 2-22
Appropriate for speech, 4-4
12-15
-------
Recruitment:
Defined, 2-19
Regulations
Occupational noise, 2-14, 2-24, 2-26 to 2-27
Health and Welfare analysis, 9-1 to 9-2
REM—see Rapid Eye Movement
Residential Exposure—see also Household Noise
Survey results, 1-1 to 1-4
Near airports, 7-1
In urban areas, 8-1 to 8-8
Rock Music
Effects, 2-18
Levels, 2-18
Safety
Field study, 3-8
Effects from communeiation interference, 6-1
Effects from stress, 7-5
Schools—see Learning
Schultz Curve
Displayed, 8-5
Senior Citizens—see Elderly
Sensori-Neural Hearing Loss
Defined, 2-6
Causes, 2-7
Sex
Hearing differences, 2-3
Effect on sleep disruption, 6-5
Shaw, W.
Studies, 3-9
12-16
-------
Sleep Disturbance
In general, Chapter 6
Effects, 6-1
Awareness, 6-1
Indirect effects, 6-1
Disruptive noise levels, 6-2
Physiological effects, 6-3
Probability of disruption, 6-3
Variance with noise level, 6-5 to 6-6
Probability of awakening, 6-5
Effects of sound quality, 6-2, 6-6
Effects of age and sex, 6-6
Effects of sleep duration, 6-5
Effects of noise duration, 6-2
Effects of sleep deprivation, 6-7
Effects of time of night, 6-3
Survey data, 6-6
Stages of sleep, 6-3
Long-term effects, 6-7
Relating to community response, 8-1
Criteria, 6-4 to 6-5
Social Interaction
Effects from communciation interference, 4-1
Effects from excessive exposure, 7-5 to 7-6
Effects from hearing loss, 2-2C
Sociocusis
Defined, 2-15
Evidence of occurance, 2-17
Socioeconomic Status
Effect on psychological response, 7-2
Relation to annoyance, 8-8
Sone
Defined, 7-3
Special Populations—see also Fetus
Children
Age
Sex
Workers
Elderly
Noise sensitive, 7-4
Affected by masking, 4-8 to 4-9
12-17
-------
Spectral Characteristics
Effect on performance, 5-23
Effect on subjective response, 7-2
Speech Interference—see Communication Interference
Standards—see Regulations
Startle Reflex—see Arousal Response
Statistics
Residential exposure, 1-1 to 1-5, 8-7 to 8-9
Societal costs, 5-5
Hearing loss extent, 2-7 to 2-8
Strategies, Control
Noise reduction, 2-24 to 2-26
Source modification, 2-25
Path alteration, 2-25
Stress, Mental—see also Annoyance
From excessive noise, 3-5, 7-1
Stress, Physical
As noise effect, 3-1 to 3-10
From industrial noise, 5-5
Subjective Response—see Psychological Effects
Psychological Response
Surveys—see also Urban Noise
Annual Housing Survey
On sleep disruption, 6-7
On community response, 8-1 to 8-8
On subjective response, 7-5
Susceptibility
To hearing loss, 2-9 to 2-10
Etfect os ex, 2-11
Testing, 2-29
Of children, 5-5
To infection or toxic substances, 3-1
12-13
-------
Svnergism
with toxic substances, 2-10, 3-8
Tasks, Noise Sensitive
Types, 5-3
Terminology—see Acoustic Terminology
Tinnitus
Defined, 2-20
Extent. 2-20
Threshold of Audibility
Normal hearing, 2-2
Threshold of Pain
Level, 2-3
Threshold Shifts, Noise Induced
Permanent, 2-7, 2-9, 2-23 to 2-24
Temporary, 2-12 to 2-13, 2-18
Predictions, 2-12 to 2-13
From loud music, 2-18
Steady-state exposure criterion, 2-24
Relation to exposure levels, 2-7
From continuous noise, 2-24
Toxic Substances
Hearing effects, 2-7, 2-10
Synergistic effects, 3-6
Susceptibility, 3-1
Traffic Noise—see also Specific Vehicle Types
As source of neighborhood dissatisfaction, 1-1 to 1-2
Population exposed to, 1-1 to 1-4
Relation to cardiovascular problems, 3-4
Traumatic Hearing Loss
Defined, 2-6
12-19
-------
Typical Noise Exposures
In Schorl study, 1-4
Hypotheticsl, 1-5 to 1-6
Ulcers--see also Digestive Disorders
A3 stress effect, 3-1, 3-5
Urban Noise
Sources, 1-1 to 1-4
Population exposed, 1-1 to 1-4
Survey results, 1-1 to 1-2, .8-7 to 8-9
Survey conclusions, 10-9
Urban Noise Survey—see Urban Noise
Undesirable Neighborhood Conditions
Noise, 1-1 to 1-2
Vasoconstriction
In startle (arousal response), 3-1
Of uterine blood vessels, 3-10
During sleep, 6-2
As stress effect, 3-2
Vehicle Noise—see Traffice Noise
Vestibular Problems—see Vertigo
Vertigo
From high-intensity noise, 5-2
Vigilance Tastes
Disruption factors, 4-2, 5-3
Walsh-Healy Public Contracts Act
Permissible exposure levels, 2-27
Weighting Schemes
A-weighting, 4-3
For measuring subjective response, 7-2 to 7-3
Stevens' Mark VII and VIII, 7-2
Zwicker's procedures, 7-2 to 7-3
12-20
-------
Womb—see Fetus
Workers—see Occupational Noise
Work Performance—see Performance Interference
Workplace
Absenteeism, 3-8
Cost of exposure, 5-5
12-21
-------
------- |