NTID300.3
COMMUNITY NOISE
DECEMBER 31, 1971
U.S. Environmental Protection Agency
Washington, D.C. 20460
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NTID300.3
COMMUNITY NOISE
DECEMBER 31, 1971
Prepared by
WYLE LABORATORIES
under
CONTRACT 68-04-0046
for the
U.S. Environmental Protection Agency
Office of Noise Abatement and Control
Washington, D.C. 20460
This report has been approved for general availability. The contents of this
report reflect the views of the contractor, who is responsible for the facts
and the accuracy of the data presented herein, and do not necessarily
reflect the official views or policy of EPA. This report does not constitute
a standard, specification, or regulation.
U.S. Environmental Protection Agency
Region 5, Library (PL-12J)
77 West Jackson Boulevard, 12th Flooi
Chicago, IL 60604-3590
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 - Price $1.75
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L..OACTION AGEKCY
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TABLE OF CONTENTS
Page
1.0
2.0
3.0
4.0
5.0
6.0
7.0
INTRODUCTION
DESCRIPTION OF THE OUTDOOR NOISE ENVIRONMENT .
2.1 Basic Physical Description
2.2 Statistical Description
RANGE OF OUTDOOR NOISE ENVIRONMENTS
3.1 Variation of Outdoor Noise Environment with Location .
3.2 Relationships Among Various Measures of the A-Weighted
3.3 Typical Outdoor Daytime Residual Noise Spectra
INTRUDING NOISES .
4.1 Constant Level Noise Intrusions
4.2 Intermittent Single Event Noise Intrusions
COMMUNITY REACTION TO NOISE POLLUTION ....
5.1 Correlation of Community Reaction with Noise
5.2 Community Reaction and Annoyance
5.3 Applicability of Noise Pollution Level and Traffic
Noise Index to Community Noise Assessment ....
THE GROWTH OF NOISE POLLUTION
6.1 Change in Intruding Noises
6.2 Change in Residual Noise
CONCLUSIONS AND RECOMMENDATIONS
7.1 Conclusions
7.2 Recommendations
REFERENCES
APPENDIX A COMMUNITY NOISE SURVEY
APPENDIX B TYPICAL NOISE SPECTRA
APPENDIX C TERMINOLOGY
1
3
3
9
17
17
26
36
41
41
44
50
50
64
66
80
80
82
89
89
93
97
A-l
B-l
C-l
III
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LIST OF TABLES
Table
Number Page
1 Example of Statistical Distribution of Outdoor Noise Analyzed 9
in Intervals of 5 dB Widths
2 Example of the Variation in the Statistical Measures of Outdoor 14
Noise Level for Several Periods in a 24-Hour Day, as a Function
of Calculation Technique
3 Comparison of Average Daytime and Nighttime Outdoor Noise 25
Levels in City and Detached Housing Residential Areas. Data
are Averages of Hourly Values During Indicated Period
4 Comparison of .Maximum Daytime and Minimum Nighttime Hourly 27
Outdoor Noise Levels in City and in Detached Housing
Residential Areas
5 Qualitative Descriptors of Urban and Suburban Detached Housing 28
Residential Areas and Approximate Daytime Residual Noise Level
(L0fJ. Add 5 dB to These Values to Estimate the Approximate
Value of the Median Noise Level (Lr/J
6 Comparison of the Mean and Standard Deviation of the 24 Hourly 30
Differences Between Graphic Level Recorder and Statistical
Measures of the Residual and Maximum Noise Levels at Each of
18 Locations
7 Comparison of the Mean and Standard Deviation of the 24 Hourly 31
Differences Between the Arithmetic Mean and the Median Lc.-.
Measures of the Outdoor Noise Level in dB
8 Accuracy in Estimating Various Hourly Noise Level Values 35
from Samples of Differing Duration
9 Examples of Intruding Noises Found in the Residential Outdoor 46
Noise Environment in This Survey
10 Factors Considered in Each of Three Methods in Use for Describing 52
the Intrusion of Aircraft Noise into the Community
IV
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Table
Number Page
11 Corrections to be Added to the Measured Community Noise 54
Equivalent Level (CNEL) to Obtain Normalized CNEL
12 Two Examples of Calculation of Normalized Community Noise 55
Equivalent Level
13 Number of Community Noise Reaction Cases as a Function 56
of Noise Source Type and Reaction Category
14a Summary of Data for 28 of the 55 Community Noise Reaction 57
Cases
14b Summary of Data for 33 of the 55 Community Noise Reaction 58
Cases
15 Effect of Normalizing Factors on 55 Community Noise Reaction 61
Cases as Measured by the Standard Deviation of the Data
About the Mean Relationship Between Community Reaction and
Normalized CNEL
16 Activities Disturbed by Noise as Reported by People Who Are 64
"Extremely Disturbed by Aircraft Noise"
17 Relationships Among Various Methods of Calculating Noise 75
Pollution Level for Data from 18 Locations
18 Residual Noise Levels (L9Q) in dB(A) for 28 Residential Locations 84
Including 11 from this Survey and 17 Locations From Measure-
ments in Los Angeles, Detroit and Boston
19 Comparison of Outdoor Daytime Residual Noise Levels (Lgr)) 87
in the Downtown City
20 Summary of Expected Community Reaction and Approximate 92
Annoyance as a Function of Normalized Community Noise
Equivalent Level
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LIST OF FIGURES
Figure
Number Page
1 A Typical Octave Band Spectrum of the Outdoor Residual Noise 4
Level in Late Evening in a Normal Suburban Neighborhood
Illustrating the Effect of the A-Weighting on the Relative
Importance of Various Frequency Bands
2 Two Samples of Outdoor Noise in a Normal Suburban 6
Neighborhood with the Microphone Located 20 Feet from the
Street Curb
3 Example of One-Half Hour Graphic Level Recordings Beginning 8
on Each Hour from Midnight Through 10:00 A.M. at a Residence
in a Normal Suburban Neighborhood
4 Histograms and Cumulative Distribution of Noise Levels for Two 11
One-Hour Periods of Data from Figure 3
5 Statistical Portrayal of Community Noise Throughout 24 Hours at 12
a Residence in a Normal Suburban Neighborhood
6 Histogram and Cumulative Distribution of the Noise Levels of 15
Figure 5 Throughout the Day
7 Daytime Outdoor Noise Levels Found in 18 Locations Ranging 18
Between the Wilderness and the Downtown City, with
Significant Intruding Sources Noted. Data are Arithmetic
Averages of the 12 Hourly Values in the Daytime Period
(7:00 a.m. - 7:00 p.m.) of the Levels Which are Exceeded
99, 90, 50, 10 and 1 Percent of the Time
8 Evening Outdoor Noise Levels Found in 18 Locations Ranging 20
Between the Wilderness and the Downtown City, with
Significant Intruding Sources Noted. Data are Arithmetic
Averages of the 3 Hourly Values in the Evening Period (7:00 p.m.
- 10:00 p.m.) of the Levels Which are Exceeded 99, 90, 50,
10 and 1 Percent of the Time
VI
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Figure
Number Page
9 Nighttime Outdoor Noise Levels Found in 18 Locations 21
Ranging Between the Wilderness and the Downtown City,
with Significant Intruding Sources Noted. Data are Arithmetic
Averages of the 9 Hourly Values in the Nighttime Period
(10:00 p.m. - 7:00 a.m.) of the Levels Which are Exceeded
99, 90, 50, 10 and 1 Percent of the Time
10 Residual Outdoor Noise Level (Lg.-.) for Day, Evening and 22
Nighttime for 18 Locations Ranging Between the Wilderness
and the Downtown City
11 Median Outdoor Noise Level (I-™) for Day, Evening and 23
Nighttime for 18 Locations Ranging Between the Wilderness
and the Downtown City
12 Outdoor Noise Level (L1(~) for Day, Evening and Nighttime 24
for 18 Locations Ranging Between the Wilderness and the
Downtown City
13 24-Hour Outdoor Noise Levels Found in 18 Locations Ranging 32
Between the Wilderness and the Downtown City, with
Significant Intruding Sources Noted. Data are Arithmetic
Averages of the 24 Hourly Values in the Entire Day of the Levels
Which are Exceeded 99, 90, 50, 10 and 1 Percent of the Time
14 24-Hour Outdoow Noise Levels Found in 18 Locations Ranging 33
Between the Wilderness and the Downtown City, with
Significant Intruding Sources Noted. Data are the Levels
Which are Exceeded 99, 90, 50, 10 and 1 Percent of the Time
from the 24-Hour Ensemble
15 Examples of Daytime Residual Noise Spectra in Low Noise Level 37
Areas (High Frequency Levels at Grand Canyon Site May be
Instrument Noise)
16 Examples of Daytime Residual Noise Spectra in Cities 38
17 Examples of Relative Daytime Residual Noise Level Spectra at 39
8 Locations Encompassing Normal Suburban to Noisy Urban
Residential Neighborhoods with Noise Levels Ranging from 43
to 55 dB(A)
VII
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Figure
Number Page
18 Range of the Relative Maximum Noise Spectra Measured 40
During the Passby of 10 Standard Passenger Automobiles
Driving on Local Residential Streets
19 Maximum Distance Between Talker and Listener for Just 42
Intelligible Conversation and for Highly Intelligible Relaxed
Conversation as a Function of Noise Level
20 Estimated Maximum Distances Between Talker and Listener
That Just Permit Intelligible Conversation and Those That
Enable Relaxed Conversation When the Outdoor Noise Level
Equals the Daytime Median Noise Level (L™) at Each of the
18 Locations
21 Noise Level Required to Mask Speech (5% Sentence Intel I i- 45
gibility) as a Function of Distance Between Talker and Listener
for Normal Voice Level
22 Average Mean Subjective Rating as a Function of Maximum 47
Noise Level in dB(A) for the British Experiment at the Motor
Industry Research Association Proving Grounds
23 Relative Daytime Outdoor Noise Levels Found in 18 Locations 49
Ranging from Wilderness to Downtown City with Significant
Intruding Single Event Noise Sources Noted
24 Community Reaction to Intrusive Noises of Many Types as a 59
Function of the Normalized Community Noise Equivalent Level
25 Community Reaction to Intrusive Noises of Many Types as a 63
Function of the Normalized Noise Level Using Original
Procedures of Rosenblith and Stevens
26 Percentage of People Who Were Ever Disturbed by Noise at 65
Home, Outdoors and at Work in London City Survey
27 Relationship Between Average Expression of Annoyance to 67
Aircraft Noise and the Composite Noise Rating, and with the
Approximate Scale for the Normalized Community Noise
Equivalent Level
VIII
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Figure
Number Page
28 Percentage of People Expressing "Very Much Annoyed" as a 68
Function of Composite Noise Rating and with the Approximate
Scale for the Normalized Community Noise Equivalent Level
29 Percentage of People Expressing "Not At All" or "A Little" 69
Annoyed as a Function of Composite Noise Rating and with the
Approximate Scale for the Normalized Community Noise
Equivalent Level
30 Comparison of Griffiths and Langdon Dissatisfaction Score Data 71
with (a) Traffic Noise Index and (b) Noise Pollution Level
31 Comparison of Griffiths and Langdon Dissatisfaction Score Data 72
with (a) Energy Average Noise Level and (b) Difference Between
Energy Average Noise Level and LO(-.
32 Relative Daytime Outdoor Noise Levels Found in 18 Locations 74
Ranging from Wilderness to Downtown City with Significant
Intruding Single Event Noise Sources Noted
33 Example of the Relationship Between Noise Pollution Level and 77
Community Reaction for Aircraft Noise, as a Function of
Outdoor Residual Noise Level
34 Example of the Effect of Turning on a Steady State Intruding 79
Noise of 60 dB(A) on Noise Pollution Level as a Function of the
"On Time" Fraction
35 Approximate Growth in Aircraft and Freeway Noise Impacted 81
Land Area Enclosed by Community Noise Equivalent Noise
Level of 65 dB
36 Approximate Growth of a Few Types of Noisy Recreational 83
Vehicles and Outdoor Home Equipment
37 Comparison of Five Surveys of Outdoor Noise Levels in 85
Residential Areas in the United States Between 1937 and 1971
IX
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1.0 INTRODUCTION
A person's acoustical environment consists of the sound that he hears at
any instant of time. The sound may be pleasant and desirable, or it may be discordant
and unwanted. In the latter case, the sound is called "noise", which is defined simply
as "unwanted sound".
If a noise is sufficiently loud, it may intefere with one's ability to con-
verse with another person, disturb sleep, add to the risk of hearing damage, or other-
wise annoy the listener. A noise which adversely affects people in this manner can be
considered to pollute the acoustical environment. Thus, noise pollution is the contam-
ination of the acoustical environment by noises which adversely affect people.
A person indoors may experience noise pollution from sources located
indoors, such as a vacuum cleaner, air conditioner, or someone else's radio. Or, he
may experience noise pollution which enters the house through a closed or partially
opened window from sources located outdoors, such as motorcycles, aircraft, and
power lawnmowers. A person outdoors is also subject to noise pollution from outdoor
sources, in addition to nearby indoor sources such as a loud radio in a room with open
windows.
All aspects of noise pollution, with the exception of occupational noise,
together with a description of the noise characteristics and potential noise control for
all principal noise sources, and a review of the legal status of noise pollution are con-
1*
tained in the Environmental Protection Agency Report to Congress.
This report addresses the part of the overall noise pollution problem
which is associated with outdoor noise in the community. It attempts to provide a
quantitative framework for understanding the nature of the outdoor noise environment
and the reaction of people and community to its various aspects. The detailed informa-
tion in this report provides backup to the summary material in the EPA report, as well
as additional material relevant to meaningful measures of the noise environment for
both future community noise monitoring and research purposes.
Superscripts refer to references at the end of this report.
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Chapter 2 contains an introduction to the basic measures of the noise
environment and the manner with which they vary throughout a 24-hour day at a single
location. Chapter 3 presents the general results of 24-hour noise surveys at 18 locations,
which ranged from the wilderness to the downtown city. The locations were deliberately
chosen to encompass the range of outdoor noise environments which affect citizens in
their daily life, outside of work. The data also provide a test of the relationship among
various measures of noise for a wide variety of noise environments.
Chapter 4 discusses the nature of some of the constant and intermittent
intruding sounds which are common in our society, and the constraints that these
intruding noises place on speech communication and other human activities. Chapter 5
discusses annoyance and community reaction to noise, developing a useful correlation
between physical measures of an intruding noise, related factors, and community
reaction. Chapter 6 discusses the growth of noise pollution over the past two decades,
and Chapter 7 contains summary conclusions and recommendations.
Appendix A gives a detailed summary of the data obtained at the
18 locations surveyed. Appendix B gives typical examples of the spectra of the
intruding noises and Appendix C contains a glossary of terms.
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2.0 DESCRIPTION OF THE OUTDOOR NOISE ENVIRONMENT
The description of community noise and its degree of noise pollution
requires description of all the noises in the outdoor acoustical environment. The out-
door noise environment varies greatly in magnitude and character among various loca-
tions throughout a community— from the quiet suburban areas bordering on form land to
the din of traffic in the downtown city canyon. It generally vaiies wi*h time of day in
each location, being relatively quiet at night when people-activities are ot a minimum
and noisier in the late afternoon during the 5 o'clock traffic rush. Its effects may be
experienced by people either in or out of doors. Thus, the task of describing community
noise is to determine the time and location variations in the outdoor noise environment
throughout the community in such a manner that the descriptions are relevant to its
effects on people, located either indoors or outdoors. This chapter reviews the basic
and statistical descriptions of the time variation of the outdoor environment at a
specific location, and Chapter 3 reviews the general range of the expected variation
with location.
2. ] Basic Physical Description
A complete physical description of a sound must account for its frequency
spectrum, its overall sound pressure level, and the variation of both of these quantities
with time. Because it is awkward to present and understand data which have three
dimensions, considerable effort has been expended during the last 50 years to develop
2
scales which reduce the number of these dimensions.
Most of the effort has been focused on combining measures of the frequency
content and overall level into a quantity proportional to the magnitude of the
sound as heard by a person. The simplest approach found to date is to electronically
weight the amplitudes of the various frequencies approximately in accordance with a
person's hearing sensitivity and sum the resulting weighted spectrum to obtain a single
number. This method is illustrated in Figure 1 for the A-weighting contained in a
3
sound level meter. The A-weighting has been available in sound level meters since
the late 1930's and has been utilized extensively for measurement of all types of sounds.
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CN
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70
60
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10000
Figure 1. A Typical Octave Band Spectrum of the Outdoor Residual Noise
Level in Late Evening in a Normal Suburban Neighborhood
Illustrating the Effect of the A-Weighting on the
Relative Importance of Various Frequency Bands
4
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Because the A-weighting is not a perfect solution for the accounting of
man's perception of the frequency characteristics of a sound, many other scales have
4-9
been developed which attempt to better quantify "loudness" and/or "noisiness."
9
One of these, the tone-corrected perceived noise level, better accounts for the ear's
frequency response function, and also has the ability to differentiate between noises
which are broadband random (roar) in nature and those which contain high frequency
pure tones (siren), penalizing the latter. For most sounds, the perceived noise level
exceeds the A-weighted noise level by 13 dB, the differences typically ranging
between 11 and 17 dB, depending primarily upon the amount of the correction for pure
tones. ' ' Because the perceived noise level scale is somewhat more exact than
the A-weighting in relating the physical characteristics of a sound to perceived noisi-
ness, particularly for aircraft noises, it has become a major element in the noise scale
,r .., . . ft 12,13
used tor certitymg aircratt.
The tone-corrected perceived noise level scale and the better loudness
summations require complex measurement instrumentation and data analysis to define a
sound. Therefore, they have found little application in the measurement of outdoor
noise in the community, where the simple A-weighted sound level meter appears to
serve the purpose quite adequately. Accordingly, the A-weighting is the principal
measure of the magnitude of sound used in this report, accounting for both spectrum and
overall level, y/
To complete the description of the outdoor noise environment at a specific
location, it is necessary to account for the temporal pattern of the A-weighted noise
level. The temporal pattern is most easily observed on a continuous graphic level
recording, such as the two 8-minute samples illustrated in Figure 2.
The first striking feature of these two samples is that the noise level varies
with time over a range of 33 dB, which is greater than an eight-fold range of noisiness.
The second major feature of the samples is that the noise appears to be
characterized by a fairly steady lower level upon which is superimposed the increased
levels associated with discrete single events. This fairly constant lower level is called
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Early Afternoon
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the residual noise level. The continuous noise one hears in the backyard at night when
no single source can be identified, and which seems to come from "all around," is an
example of residual noise. Distinct sounds which are superimposed on the residual noise
level, such as the aircraft overflight, cars, and dogs barking (Figure 2) can be classi-
fied as intrusive noises.
The third feature in these two samples is the difference in the noise level —
time patterns among the various sounds. The noise level of the aircraft in this example
is above that of the residual noise level for approximately 80 seconds, whereas the noise
levels from the cars passing by on the street are above the residual noise level for much
shorter durations which range between about 5 and 20 seconds. Clearly, if the noise
associated with these single events were of sufficient magnitude to intrude on an indi-
vidual's activities— conversation, thinking, watching television, et cetera — the dura-
tion factor might be expected to affect his degree of annoyance. Similarly, it might
be anticipated that the number of times such an event recurred also would affect his
degree of annoyance.
The wealth of detailed data contained in continuous recordings of this type
is further illustrated in Figure 3 by the half-hour samples taken at the beginning of each
hour from Midnight to 10:00 a.m. This example shows both the short time variations
associated with single event noises and the longer time changes in the level, as well as
in the characteristics of the temporal patterns. The residual noise level decreases from
approximately 40 dB(A) at Midnight to 30 dB(A) between 4:00 a.m. and 6:00 a.m., and
then increases to about 42 dB(A) at 10:00 a.m. Aircraft noise is generally absent
between Midnight and 7:00 a.m., after which it becomes the dominant intrusive noise.
Local vehicle traffic is generally less frequent in the 1:00 a.m. to 7;00 a.m. period,
after the teenagers have returned home for the night and prior to the adults starting to
drive to work.
The data from these continuous noise recordings is very instructive in under-
standing the nature of the outdoor noise environment at any neighborhood location.
However, to quantify an outdoor noise environment at one location so that it can be
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Figure 3. Example of One-Half Hour Graphic Level Recordings Beginning on Each Hour from
Midnight Through 10:00 A.M. at a Residence in a Normal Suburban Neighborhood.
Events Identified by the Following Letter Code: a - Jet Aircraft; ap - Propeller
Aircraft; c - Automobile; cb or b/c - Automobile in Background; d - Dog;
t - Truck; pu/t - Pickup Truck; tb - Truck in Background. The Symbol /
Indicates the Time History Trace, with Letter Codes Above and Below It.
8
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compared with that at others, it is necessary to simplify its description by eliminating
much of the temporal detail. One way of accomplishing this simplification is to
measure the value of the residual noise level and the values of the maximum noise
level for specific single event sounds at various times during the day, using either a
simple sound level meter or the continuous graphic level recording of its output.
Another method of quantifying the noise environment is to determine the statistical
properties of the noise level by attaching a statistical analyzer on the output of the
sound level meter. These methods for simplifying the third dimension of the noise
environment will be illustrated in the next section.
2.2
Statistical Description
A statistical analysis of the noise level gives the percentage or TOTOI time
that the value of the noise level is found between any two set limits. Such data can
be presented directly in the form of histograms, or be used to obtain a cumulative distri-
bution in terms of the "level exceeded for a stated percentage of time." For the sample
statistical distribution of Table 1, the noise level exceeds 60dB(A) for 1 percent of the
hour, 55dB(A) for lOpercent of the hour, 50dB(A) for 50 percent of the hour, and 45 dB(A)
for 90 percent of the hour. These noise levels are abbreviated symbolically as L^, L,n,
l_50 and LOQ, respectively.
Table 1
Example of Statistical Distribution of Outdoor Noise Analyzed
in Intervals of 5 dB Widths
Interval in
dB(A)
61 through 65
56 through 60
51 through 55
46 through 50
41 through 45
Percent of
Total Time
1
9
40
40
10
Cumulative
Percent of
Total Time
1
10
50
90
100
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Histograms and cumulative distribution for the noise levels are given in
Figure 4 for two hours of the data, illustrated previously in Figure 3. The histogram
for the hour between 5:00 a.m. and 6:00 a.m. is almost symmetrical, indicating a
gaussian or normal distribution. However, the histogram for the hour between 8:00 a.m.
and 9:00 a.m. is very non-symmetrical, indicating a skewed non-gaussian distribution.
This skewed distribution between 8:00 a.m. and 9:00 a.m. is the result of the large per-
centage of time during which noise was present from aircraft overflights.
Both the direct reading and the statistical methods have been applied to a
24-hour recording of the outdoor noise level at a suburban residential location. The
variation of the hourly, and the day (7:00 a.m. - 7:00 p.m.), evening (7:00 p.m. -
10:00 p.m.) and nighttime (10:00 p.m. - 7:00 a.m.) values of various statistical
measures, together with the minimum and maximum values read from a continuous
recording, are summarized in Figure 5.
For purposes of this report, the level exceeded 90 percent of the time
(LO_) was selected as an approximate measure of the residual noise level when there
were no identifiable steady-state or frequent recurring single event noises present. As
illustrated in Figure 5, the hourly values of LQn compare favorably with the hourly
values of the residual noise levels read from graphic level recordings, which in turn
generally compare well with the average minimum values obtained when reading a
sound level meter.
The median noise level (L/-/J is a useful measure of the "average" noise
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environment in the sense that one-half of the time it is quieter and one-half of the time
it is noisier than Lrn« Both L n and L are often used to represent the higher-level
shorter-duration sounds. However, as shown in the example of Figure 5, the maximum
noise levels in an hour are often much greater than the highest statistical measure
(L,) which was used in the analysis, indicating that these maximum noise levels occur
for less than 1 percent of the time during the period analyzed.
The dashed line in Figure 5, labeled L , is the energy equivalent noise
level (L ) which accounts for both the duration and the magnitude of all the sounds
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same energy during the period analyzed as that of the actual time-varying noise. The
energy equivalent noise level is one of the most important measures of the outdoor
noise environment for the purpose of correlating noise and community reaction.
All of the statistical measures in Figure 5 show the typical daytime-night-
time variation in noise level. In this example, the residual noise level drops sharply
after midnight reaching a minimum value between 4:00 a.m. and 5:00 a.m., and
rises between 6:00 a.m. and 8:00 a.m. to its almost constant daytime value. This time
variation of the noise is generally well correlated with the amount of human activity,
and particularly with the amount of vehicular traffic, which is generally considered
to be the basic source of the residual noise level in urban areas.
These statistical measures simplify the problem of quantifying the outdoor
noise level and will be used in this report to compare the outdoor noise environments
in various places. However, they must be supplemented by other observations if one is
to understand anything of the character of the outdoor noise environment beyond the
simple statistics of the noise levels. Further, they may be misleading if the character
of the noise environment changes significantly within the period analyzed statistically.
The values of the statistical quantities given for the day, evening and night
periods in Figure 5 represent the arithmetic average of the hourly values measured
during each period. The average of the hourly values of any one of the statistical
quantities during a period should be equal to the value computed directly from
the ensemble of the data for the entire period if the characteristics of the noise remaii
constant (or stationary) during the period. However, if Hie characteristics change
within the period, these two methods of calculation may yield different answers.
Table 2 gives the magnitude of the differences between these two
calculation methods. Only small differences occurred during the day and evening periods,
indicating that the noise characteristics are relatively stationary within each of these
periods. However, larger differences of the order of 3 to 5 dB are found for the Lgn
and L values in the night and 24-hour periods, indicating the noise level character-
istics are non-stationary. These indications are confirmed by inspection of Figure 5
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which shows that the noise has a significantly lower level in the hours between 1:00 a.ti.
and 7:00 a.m.
Table 2
Example of the Variation in the Statistical Measures of Outdoor Noise
Level for Several Periods in a 24-Hour Day, as a
Function of Calculation Technique
for the Data of Figure 5
Variable
L90
L50
ho
Hourly Mean*
Period Value**
A
Hourly Mean
Period Value
A
Hourly Mean
Period Value
A
Day
41 .9
41.6
0.3
46.8
47.1
-0.3
57.4
58.2
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* Hourly Mean is the arithmetic mean of the hourly values.
** Period Value is calculated from the statistical ensemble for the
entire oeriod.
A second indication of a difference in the character of the various time
periods i: given by their distributions in Figure 6. The bi-modal distributions for both the
night and 24-hour tims period^ results from the many hours of relatively low values
during the night. Clearly, "nighttime," as far as the quiet noise environment is con-
cerned in this particular example, occurred between approximately 1:00 a.m. and
7:00 a.m., rather than between the arbitrary limits of 10:00 p.m. and 7:00 a.m.
14
-------
Day (7:00 a.m. - 7:00 p.m.)
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Figure 6. Histogram and Cumulative Distribution of the Noise Levels of
Figure 5 Throughout the Day
15
-------
As shown in Table 2, the differences in calculation method affect the
extreme statistical values, L _ and L , more than the central statistical value, !_„.
This is as would be expected, since a significant change for only 10 percent of the
time during a period is required to affect the former two quantities. Obviously, more
extreme measures, such as L. and LQQ, would be even more sensitive to changes in
the character of the noise.
This discussion clearly indicates the danger in applying statistical analysis
to non-stationary noise environments, in that the results obtained for one environment
may or may not afford a valid comparison to those obtained in another environment,
depending on how stationary each environment is. To minimize the problem and provide
a consistent approach in this report, all period values have been calculated by averaging
the hourly values, except where noted. Secondly, the principal definition of outdoor
noise at various locations emphasizes the daytime noise characteristics which tend to be
more stationary in character than the noise in other periods.
16
-------
3.0 RANGE OF OUTDOOR NOISE ENVIRONMENTS
In order to define for fhis report the range of outdoor noise environments
encountered by people in their normal activities, a series of 24-hour outdoor noise
recordings was made at each of eighteen (18) sites. This exploratory measurement sur-
vey was planned to sample noises in all types of locations, from the wilderness to the
downtown city, with major emphasis in the suburban and urban residential areas, and to
include examples of some of today's more significant noise pollution problems. Thus,
the survey presents a preliminary cross-section of the noise environment; but since it
was not designed to be weighted by population density, it cannot give a true statistical
picture of the noise environment in terms of a national baseline. This chapter describes
the general results of the survey in terms of the variation of several statistical measures
of the noise environment with both location and time of day, and discusses the inter-
relationships among some of these measures. A detailed summary of the measurement
sites and data together with the survey instrumentation are given in Appendix A.
3.1 Variation of Outdoor Noise Environment with Location
The range of daytime outdoor noise levels at the 18 locations is presented
in Figure 7. The locations are listed from top to bottom of the figure in descending
order of their daytime residual noise levels (Lon). The noisiest location, which is out-
side of a 3rd floor apartment overlooking an 8-lane freeway, is at the top of the list
with its daytime residual noise level of 77 dB(A). The rural farm is next to the bottom
of the list with its daytime residual noise level of 33 dB(A).
This difference of 44 dB in the residual noise levels of these two locations
constitutes a large range in noise climate. Its magnitude clearly implies that all citizens
do not enjoy the same "quality" in their noise environment. In fact, the owner of the
3rd floor apartment near the freeway has trouble keeping the apartment rented for more
than a month to any one tenant. His problem is not surprising, since the outdoor noise
level is sufficiently high to render normal speech communication difficult indoors, even
when the windows are closed.
17
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The Grand Canyon measurement was made on the north rim, at a remote
camping site. Its outdoor daytime residual noise level (LQJ of 16 dB(A) is near the
internal noise threshold of the field measurement system and should be representative of
the quietest locations in this country. The difference between this extremely low
residual noise level and the much higher noise levels in the city is representative of the
contribution of man and machine to the outdoor noise environment.
Figures 8 and 9 present similar data for the evening and nighttime periods.
The order in which the locations are presented is the same as that used in Figure 7.
However, unlike the data in Figure 1, where the LQ.-. values increase monotonically
from bottom to top, some irregularity can be seen among adjacent !_„_. values in Figures
7 and 8. This irregularity indicates that the magnitude of the variation of the noise
with time throughout a 24-hour period is different at different locations.
The magnitudes of the variation in the L_n, L^ and L values for day,
evening and night are presented in Figures 10 through 12. At two locations in Figure 10,
both the evening and the nighttime values of the residual noise level exceed the daytime
values because of crickets. At location P, which was in a quiet residential hillside
canyon, the noise from the crickets was the dominant feature in the noise environment
from 8:00 p.m. to 6:00 a.m. At the Grand Canyon, the crickets were of primary
significance in the evening and early nighttime.
For the remainder of locations, except downtown Los Angeles, the evening
noise levels were approximately equal to the daytime values, whereas the nighttime
values were significantly lower. In downtown Los Angeles, the noise drops considerably
in the evening, after commercial activity ceases.
As shown in these figures, the noise environments in city locations (e.g.,
downtown Lo:. Angeles, tenement in New York, apartment adjacent to freeway and
urban shopping center) are distinctly higher in level than are those in the suburban and
urban residential areas. In this small sample of measurement locations, the average
residual and median noise levels are over 20 dB greater at the city locations than in the
detached residential housing areas in both daytime and nighttime, as seen in the com-
parisons in the first two columns of Table 3.
19
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The average of the differences between the daytime and nighttime residual
noise levels at each of the 11 locations in the residential areas is 5.8 dB, slightly less
than the 8.3 dB difference for the 4 city locations. However, in Table 4, a similar
comparison of the differences between the maximum daytime and minimum nighttime
residual noise levels showed a difference of 13 dB, averaged over the same 11 residential
locations, and 15.2 dB for the city locations. This latter comparison betwe?en maximum
and minimum levels gives full weight to the "quiet" nighttime period which was illus-
trated in the Figure 5 example of a "normal suburban residential" neighborhood.
The average value of the daytime residual noise level in residential areas
was 45.6 dB (A) for this limited survey. This value lies on the borderline between
the daytime residual noise level ranges chosen to represent "normal suburban" and
"urban residential" areas, as given in Table 5. Since the qualitative descriptions of
these 11 residential locations included four descriptive categories which ranged from
"quiet suburban residential" to "noisy urban residential," it is not surprising that the
average residual noise level for these locations is close to the average of the four
categories in Table 5.
3.2 Relationships Among Various Measures of the A-Weighted Noise Level
There are several methods which have been used to report data which
14-22
describe the outdoor noise environment. In general, these methods are related
to the type of instrumentation utilized for measurement, the purpose of the measure-
ments, and sometimes to the time-varying characteristics of the noise which is measured.
The degree of sophistication of the instrumentation ranges from the simple sound level
meter, which is read directly by eye, to a complex system involving computer analysis
of the statistics of the noise levels. The duration of the noise samples utilized for
measurement has varied greatly, generally being relatively short for direct reading of
sound level meters and sometimes almost continuous for graphic level or tape-recorder
systems. Obviously, the reported results are influenced by the methods employed to
obtain the data. Some indication of the degree of this influence can be obtained from
the results of this survey, which include a wide variety of types of environments.
26
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Table 5
Qualitative Descriptors of Urban and Suburban Detached Housing
Residential Areas and Approximate Daytime Residual Noise Level (Lgn).
Add 5 dB to These Values to Estimate the Approximate
Value of the Median Noise Level (Lrn)«
Description
Quiet Suburban Residential
Normal Suburban Residential
Urban Residential
Noisy Urban Residential
Very Noisy Urban Residential
Daytime Residual Noise Level in dB(A)
Typical Range Average
36 to 40 inclusive
41 to 45 inclusive
46 to 50 inclusive
51 to 55 inclusive
56 to 60 inclusive
38
43
48
53
58
28
-------
A comparison was made for each of the 24 hours ot each site between the
residual level read from the graphic level recording and the lower two statistical
measures, !_on and L o. A similar comparison was made between the maximum noise
levels and the upper two statistical measures, L-n and L . The mean difference and
standard deviation for each of the four comparisons is tabulated by location in Table 6.
The residual level for these data, as read on the graphic level recorder,
averages approximately 0,9 dB below the LO_ value and about 1.3 dB above the L ^
value, with a standard deviation of about 2 dB in both cases. These results indicate
that [_on is a reasonable choice for residual noise level, although an intermediate value
between L0f) and L , such as L , might be slightly better.
The results for the maximum noise level comparison indicate that L.-.
underestimates the maximum noise level by over 17 dB and L, underestimates it by
about 9 dB.
The actual mean magnitudes of the underestimation of L ~ range from
approximately 9 to 30 dB, with a standard deviation of 7.6 dB for all of the 432 hourly
samples. The range for the underestimations of L is from approximately 4 to 14 dB,
with a standard deviation of 4.8 dB. Clearly, l_in is a poor estimator of the maximum
noise level at almost all locations, and L , although a much better estimator, cannot
be considered accurate. Thus, whereas the residual noise is estimated with reasonable
accuracy by a statistical measure between l_on and L , the maximum noise level is
not estimated with equal accuracy by an equivalent statistical measure for higher
levels. To obtain accuracy with the latter statistical measures, it would be necessary
to consider levels which are exceeded 0.1 percent and 0.01 percent of the time.
Table 7 presents a similar comparison between differences between the
arithmetic mean and the median (!-,-«)• The results show excellent consistency between
these two measures of the central tendency of the noise level, with the arithmetic mean
averaging 0.78 dB greater than L^, with a standard deviation for the 432 samples of
0.8 dB.
29
-------
Table 6
Comparison of the Mean and Standard Deviation of the 24 Hourly Differences
Between Graphic Level Recorder and Statistical Measures of the Residual and
Maximum Noise Levels at Each of 18 Locations
Location
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
Average
All
Locations
Residual Noise Level Comparison
in dB
24 Hour
Mean
RL-L99
-0.85
-0.15
2.05
1.75
1.87
2.28
-2.33
2.18
1.04
1.51
1.68
1.62
2.08
1.99
1.79
2.21
2.01
1.28
1.33
CTRL-L99
2.60
2.56
1.19
1.65
1.24
1.24
1.37
1.26
1.10
0.98
1.20
1.20
1.29
1.21
1.42
1.81
1.65
1.56
1.95
24 Hour
Mean
RL-L9Q
-3.94
-2.44
-1.50
0.17
-1.20
-0.50
-3.41
-0.44
-1.68
0.28
-0.19
-0.35
0.29
0.37
-0.90
-0.40
-0.10
-0.39
-0.91
CTRL-L90
4.65
1.90
1.16
1.35
0.51
1.55
1.89
1.29
1.17
1.11
0.84
1.19
1.07
0.66
1.94
2.57
1.10
2.37
2.19
Maximum Noise Level Comparison**
in dB
24 Hour
Mean
ML-L1Q
9.70
9.48
17.62
13.50
12.68
30.20
10.40
14.75
21.78
16.15
24.65
18.61
22.41
23.02
19.51
19.24
16.65
18.68
17.73
GML-L1Q
3.09
4.52
4.96
5.45
3.97
8.88
3.39
2.45
6.12
5.02
6.16
3.51
7.00
5.66
5.37
3.90
4.37
8.70
7.63
24 Hour
Mean
ML-L
5.08
3.77
11.04
9.28
8.07
8.78
4.10
6.66
10.87
7.85
10.36
10.42
12.26
14.32
9.73
11.35
9.24
7.20
8.91
CTML-LI
2.62
2.97
4.14
4.78
3.39
3.87
3.45
2.07
4.21
3.61
4.18
3.19
5.87
5.19
3.70
3.07
4.86
4.90
4.85
**Residua| Noise Level Read from Graphic Level Recordings is abbreviated RL
Maximum Noise Level Read from Graphic Level Recordings is abbreviated ML
30
-------
Table 7
Comparison of the Mean and Standard Deviation of the 24 Hourly
Differences Between the Arithmetic Mean and the Median
Measures of the Outdoor Noise Level in dB
Location
A
B
C
D
E
F
G
H
I
Mean*
Difference
0.09
0.40
0.18
0.32
0.48
2.68
0.66
0.90
0.61
Standard
Deviation
0.31
0.45
0.27
0.24
0.26
0.66
0.51
0.39
0.57
Location
J
K
L
M
N
O
P
Q
R
Composite of A through R
Mean*
Difference
0.78
1.01
0.49
1.28
0.58
0.98
0.80
0.53
1.22
0.78
Standard
Deviation
0.51
0.59
0.32
0.57
0.31
0.67
0.91
0.47
1.21
0.80
Jf
Mean of 24 Values of (Arithmetic Mean - L
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variables among past noise surveys and may have significant consequences for the
resulting data.
To obtain a preliminary evaluation of the magnitude of the errors asso-
ciated with various sample lengths, three 3200-second recordings were selected for
analysis. The three samples were selected to cover a wide range of types of fluctuations
in level. One sample, from the freeway location, was selected to represent an almost
gaussian and steady-state intruding noise which was expected to be reasonably stationary
throughout. The second sample was selected to be typical of many suburban neighbor-
hoods with a combination of local single events plus aircraft overflights. The third
example was an urban residential neighborhood which had four significant aircraft
noise events during the hour.
Each recording was statistically analyzed in 64 sequential 50-second
samples. The raw data for sequential pairs of samples were then combined and used to
obtain 32 values for 100-second samples. Then, the raw data for sequential pairs of
100-second samples were combined into sixteen 200-second samples and analyzed.
This combinatorial process was continued until the entire 3200-second recording was
analyzed as a single sample.
The average difference between the value of a given measure from the
3200-second sample and the value for each of the other samples was calculated. The
mean and standard deviation of these differences is given for L , L.-., L,-n, LQn/
and L in Table 8. The mean difference for all measures of the freeway noise (A)
eq '
is less than 1 dB for sample durations of 100 seconds and greater. To obtain the same
accuracy at locations M and K, requires a minimum sample duration of 800 seconds.
The largest sampling errors are exhibited by L , as might be expected. At
position K, the mean error in L ranges between about 9 and 19 dB, with respective
standard deviations of about 11 and 8 dB for sample lengths of 400 and 50 seconds. The
significance of these large mean errors in L] is that only a few of the samplers are
affected by the highest level single-event noises. The most stable value is L_n, which
34
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has only a small mean error for all sample lengths, as expected. However, to obtain a
standard deviation of less than 1 dB for L™ required a sample length greater than 800
\J\J
seconds at both positions M and K, although 50 seconds were adequate for this result at
position A.
The potential magnitude of the errors in estimation of the statistical
measures of the higher noise levels is obviously large for any noise environment which is
characterized by significant single events. Consequently, such measures should be
applied with great caution unless the fraction of time during which data are acquired
is at least 25 percent of the total time in the period examined, and preferably 50 per-
cent of the total time. However, even with this latter constraint, the standard
deviation for L and l_in exceeds 2 dB at position M and is almost 2 dB for L. at
position K. Assuming these errors are normally distributed, a standard deviation of
2 dB for a given sample length implies that the result for a single measurement has a
95 percent probability of being within -4 dB of the true value.
3.3 Typical Outdoor Daytime Residual Noise Spectra
Typical outdoor daytime residual noise spectra are given in Figures 15 and
16. All exhibit the same general shape, with their maxima at low frequency.
Figure 17 shows spectra for 8 residential locations, normalized by their
individual A-weighted levels. The relatively small range of these relative levels, par-
ticularly above 300 Hz, is indicative of their essential similarity. With the exception
of the effects of wildlife, this residual noise is primarily due to automotive transport.
The low frequency maximum results from the integrated effect of automobile noise over
23
an extended area. The remainder of the spectrum is controlled by automotive noise
from a more limited area because atmospheric attenuation and shielding reduce the
higher frequency noise transmission. Consequently, the medium and high frequency por-
tion of the spectrum is relatively similar to the spectra for nearby automobiles, illus-
trated in Figure 18.
36
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3rd Floor Hi-Rise — Downtown Los Angeles
(80 dB(A))
2nd Floor Tenement — New York
(68 and 71 dB(A))
il
I I
100 2 5 1000 2
Frequency in Hertz
10,000
Figure 16. Examples of Daytime Residual Noise Spectra in Cities
38
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Frequency in Herrz
10,000
Figure 17. Examples of Relative Daytime Residual Noise Level Spectra at
8 Locations Encompassing Normal Suburban to Noisy Urban
Residential Neighborhoods with Noise Levels
Ranging from 43 to 55 dB(A)
39
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Figure 18. Range of the Relative Maximum Noise Spectra Measured
During the Passby of 10 Standard Passenger Automobiles
Driving on Local Residential Streets
40
-------
4.0 INTRUDING NOISES
There are two basic types of Identifiable intruding noises which increase
the outdoor noise level above the residual noise level — steady or quasi steady state con-
stant level noises and intermittent single event noises. A steady or nearly constant level
noise intrusion may result from a nearby freeway, industry, or a neighbor's residential
air conditioner. The intermittent single event noise is exemplified by the noise from an
aircraft flyover, a single car pass-by, or a dog who barks for a short time. Both types
of identifiable intruding noises can represent noise pollution.
4.1 Constant Level Noise Intrusions
One of the best known examples of constant level noise intrusion is the
noise environment within a busy city. The high daytime noise levels within the city
make it difficult to have an intelligible face-to-face conversation at normal voice
levels outdoors. For example, if the outdoor noise level is 76 dB(A), a condition com-
monly encountered when walking along downtown city sidewalks, it is necessary to talk
in a raised voice to achieve intelligibility at a 2-foot distance.
The maximum distances for intelligible conversation at various voice
levels are given in Figure 19. These criteria have been applied to the outdoor daytime
median noise levels measured at each of the 18 locations in the exploratory survey to
determine the maximum distances for intelligible conversation at each location. The
median noise level, rather than the residual noise level, has been selected for evalu-
ating the effects of the outdoor noise environment on speech communication since the
median noise level more nearly represents the "typical" or "average" noise environment.
The calculated distances, summarized in Figure 20, illustrate the restrictions in voice
communication distances which accompany the higher noise levels in the city.
Similar calculations show that the maximum distances for normal voice
conversation outdoors in a "very noisy urban residential" area are 3 to 5 feet, according
to the range of noise levels for this category in Table 5 in Section 3.1. Clearly, areas
with even higher outdoor median noise levels have very limited utility for outdoor con-
versation, and consequently are poorly suited for detached housing land use. Also, the
41
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noise associated with the "very noisy urban residential" area of Table 5 is sufficiently
high to restrict the amount by which doors and windows can be opened if one is to retain
a desirable indoor noise environment for relaxed conversation.
The noise levels associated with the "quiet suburban residential" area of
Table 5 permit just intelligible normal voice conversation at distances ranging between
30 and 50 feet. The ability to communicate in a normal voice over these distances
is very useful in a neighborhood with large lots. However, if the noise level
is so low that the distance for intelligible conversation in normal voice approaches the
distances between neighbors, it becomes difficult to have a private conversation. The
26 27
noise level calculated ' to mask speech for normal voice level (male) so that only
5 percent of the sentences are intelligible/is given in Figure 21r as a function of distance
between talker and listener for two assumed conditions. There is a 9 dB difference
between these two conditions and the lower value probably is more representative of the
typical situation which generally has some shielding.
These results indicate that the residual noise level required to obtain
privacy for neighbors separated by a 50-foot distance would have to be of the order of
41 dB(A), assuming random orientation of the talker relative to the neighbor and 5 dB
of shielding. This residual noise level is approximately that of the normal suburban
community.
These considerations of speech intelligibility and privacy suggest that
there is both a maximum and a minimum bound to the outdoor noise levels which are
compatible with reasonable enjoyment and full use of patios, porches and yards. The
upper bound for speech intelligibility appears to be in the range of the "very noisy
urban residential" category of Table 5, and the lower bound for speech privacy is a
function of the distance and shielding between neighbors.
4.2 Intermittent Single Event Noise Intrusions
A great number of intermittent single event noises were measured during
the exploratory survey. A brief sampling of the various types of noises and their maxi-
mum noise levels at some of the 18 measurement locations is given in Table 9, and some
44
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70
60
50
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30
20
1 I I
No Shielding and Face-to-Face
Orientation
5 dB Shielding
and Random
Orientation
I
1 I
I I I I
10
20 50 100 200
Distance Between Talker and Listener in Feet
500
Figure 21. Noise l,evel Required to Mask Speech (5% Sentence Intelligibility)
as a Function of Distance Between Talker and Listener for Normal Voice Level
45
-------
Table 9
Examples of InJruding Noises* Found in the Residential Outdoor
Noise Environment in this Survey
Type of Source
Type of
Neighborhood
Maximum Noise*
Level dB(A)
4-Engine Turbofan Aircraft Landing
Fire Engine Siren
Diesel Truck
2-Engine Turbofan Aircraft Takeoff
Street Sweeper
Construction Crane
Construction Air Wrench
Train Passing
Ready Mix Cement Truck
Motorcycle
Rapid Transit Bus
Garbage Truck
Freeway Automobile Traffic
Automobile Horn
Automobile Sports Car
Tire Squeal
4-Engine Turbofan Landing
Automobile on Main Street
Ice Cream Truck with Music
Private Aircraft Sight-Seeing
4-Engine Aircraft Overflight
Car Brake Squeal
Helicopter Overflight
Power Lawnmower
People on Beach
Children Playing
Lawn Edger
Cat Fight
Dog Barking
Stationary Train with Engine Idling
Automobile at Distance
Milk Truck
Rooster
Radio Playing Music
Crickets in Evening and Night
Bird
Children Playing
Aircraft at High Altitude
Noisy Urban Residential
Downtown City
Freeway Apartment
Urban Residential
Urban Residential
Downtown City
Downtown City
Urban City
Downtown City
Urban Residential
Downtown City
Urban Residential
Freeway Apartment
Urban Residential
Normal Suburban
Downtown City
Urban Residential
Small Town Residential
Urban Residential
Grand Canyon
Normal Suburban
Urban Residential
Urban Residential
Urban Residential
Resort
Urban Residential
Small Town Residential
Urban Residential
Normal Suburban
Urban Residential
Normal Suburban
Normal Suburban
Farm
Urban Residential
Quiet Residential
Normal Suburban
Normal Suburban
Grand Canyon
100
95
90
88
87
85
85
84
84
84
84
83
80
78
78
78
74
73
70
70
70
68
68
68
65
64
62
60
60
55
55
54
54
52
50
45
44
40
* Note that these levels are as measured at the various locations and are not indicative
of relative source noise.
46
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of their spectra are given in Appendix B. The ranking of levels in Table 9 has no mean-
ing with respect to the relative noise output of the various sources, since the measure-
ments are essentially at random distances from the sources. The maximum noise levels
for these events at the various locations range from 100 dB(A) for a 4-engined turbofan
at an altitude of a few hundred feet distance during landing to 40 dB(A) for a similar
aircraft probably at an altitude of 30,000 to 35,000 feet during cross-country cruise.
They are illustrative of the great variety of the noises encountered in outdoor environ-
ments.
Obviously, many of these single event noises interfere with speech and
other activities for brief intervals of time. However, their impact is not as easily quanti-
fied in terms of speech interference as were the constant level noise intrusions. One
method for estimating the magnitude of the intrusion for single event noises is to ask
people to rank the acceptability of a series of noises at differing levels. One of the
most comprehensive recent studies of the subjective judgment of the noisiness of vehicle
28
noise was conducted in England at the MIRA Proving Grounds. The results are sum-
marized in Figure 22. These results, obtained with relatively low residual noise levels,
indicate that when the maximum noise level of the vehicle during its pass-by was less
than 72 dB(A), it was judged quiet by the average observer. When the maximum noise
level was between 72 and 82 dB(A), it was judged acceptable, and above 82 dB(A) it
was judged noisy. These data are consistent with the apparent general acceptance of
maximum levels in the range of 62 to 70 dB(A), which result from pass-bys on residential
streets of standard passenger automobiles.
Although these results are useful in assessing the potential noisiness of an
isolated single event, they do not necessarily account for the cumulative effect of
multiple occurrences of single events. When a single event is of sufficient magnitude
and duration, or repeated many times, it will add to the total noise energy in the hour,
increasing the value of the equivalent noise level (L ). If the event is repeated often
enough so that its total duration exceeds one percent of the hour, it will increase the
value of L,, and if its total duration exceeds 10 percent of the hour, it will increase
46 a
-------
D)
c
&
5
u
4
6'0
70
80
90
Maximum A-Weighted Noise Level in dB re 20
Quiet
^— Acceptable
Noisy
100
Excessively •*•]
Noisy I
Figure 22. Average Mean Subjective Rating as a Function of Maximum Noise
Level in dB(A) for the British Experiment at the Motor Industry Research
Association Proving Grounds?8 Nineteen Vehicles, Including Trucks,
Automobiles and Motorcycles were Judged Twice in Each of
Three Different Operating Modes by 57 Observers
(Data Collapse and Figure from Galloway29)
47
-------
the value of l_1f.. These effects are illustrated in Figure 23, which shows the values of
L , L-. and L, relative to the value of the residual noise level for daytime at each of
eq 10 1 '
the 18 locations. For most of the locations, L n is approximately 10 dB greater than
""on* ^ ^e ^ 'oca'''ons where significant intruding noises were noted, both L. and
L tended to be significantly higher relative to Lor. than at locations where significant
eq VU
intruding sources were not noted. However, !_.„ only showed increases in 4 of the
cases. The utility of L in measuring the cumulative magnitude of intruding noises
will become apparent in the following chapter, when it is used to relate the reaction
of communities to intruding noises of all types.
48
-------
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P. -41
-------
5.0 COMMUNITY REACTION TO NOISE POLLUTION
Both types of noise pollution, the constant high level noise intrusion of
the downtown city, and the intermittent single event noise intrusions in the suburban
and urban residential areas, interfere with speech and other human activities. The down-
town city type of noise environment has been recognized for centuries as undesirable for
residential living. The single event type of noise intrusion has been experienced along
railroad tracks for the last century and may be one of the reasons why land near rail-
roads is not generally considered desirable for residential construction.
However, in the last 20 years, there has been a very large growth in both
types of pollution due to the introduction of new types of noise sources into suburban
and urban residential communities. These sources, such as jet aircraft, urban freeways,
new industrial plants, and homeowner equipment, have created numerous community
noise pollution problems. These problems have provided significant data and insight
relating to community reaction and annoyance, and stimulated the development of
several indices for measurement of the magnitude of intruding noises.
5.1 Correlation of Community Reaction with Noise
The advent of the commercial jet aircraft initially increased the maximum
noise levels at some locations around major airports by 10 to 20 dB. These increases in
noise caused widespread complaints and various forms of legal action from citizens living
in neighborhoods located in the vicinity of several civil airports. This situation paral-
leled earlier history of military jet operations by the Air Force after World War II,
although only a few Air Force operational bases were close to cities and towns. Unfor-
tunately, the civil airports, which accounted for the majority of the early commercial
jet operations, were located near the major cities which they served. Further, they were
becoming surrounded by homes constructed in the post-war building boom. As jet oper-
ations and jet airports continued to grow in number, the airport noise problems tended to
spread through wider areas of the community and to an ever-increasing number of
communities.
50
-------
The Air Force and other governmental agencies began to investigate the
relationships between aircraft noise and its effect on people in communities in the early
1950's. This early research resulted in the proposal of a model by Rosenblith and
30
Stevens for relating aircraft noise intrusion and the probable community reaction.
This model, first published by the Air Force, accounted for the following seven (7)
factors:
• Magnitude of the noise with a frequency weighting for hearing
response.
• Duration of the intruding noise (10 log relative duration).
• Time of year (windows open or closed).
• Time of day noise occurs.
• Outdoor noise level in community when the intruding noise is not
present.
• History of prior exposure to the noise source and attitude toward its
owner.
• Existence of pure tone or impulsive character in the noise.
Corrections for these factors were generally made in 5 dB intervals since
many of the initial relationships were based solely on the intuition of the authors, and
31-33
it was considered difficult to assess the response to any greater degree of accuracy.
34
This method was incorporated in the first Air Force Land Use Planning Guide in 1957,
and was later simplified for ease of application by the Air Force and the FAA.
Many other methods have been proposed for describing the magnitude and
duration of repeated single event type noise, with primary application to airport noise
problems. Most of these methods represent an evolution of the community noise reaction
model and consider at least some its principal factors. The factors considered by three
of these methods for calculating the magnitude of noise intrusion are summarized in
Table 10, and additional details of the calculation procedure are given in Appendix C.
35
The composite noise rating (CNR) was introduced in the early 1960's
qz
and has been widely used by Federal agencies. The noise exposure forecast (NEF) is
51
-------
Table 10
Factors Considered In Each of Three Methods in Use for Describing
the Intrusion of Aircraft Noise into the Community
Factor
Composite
Noise
Rating
(CNR)
Noise Exposure
Forecast
(NEF)
Community Noise
Equivalent Level
(CM EL)
Basic measure of single event
noise magnitude
Maximum
perceived
noise
level
Tone Corrected
perceived
A-weighted noise
level
noise
level
Measure of duration of
individual single event
None
Energy
integration
Energy integration
Time periods during day
Daytime (7 AM-10 PM)
Nighttime (10 PM-7 AM)
Daytime (7 AM-7 PM)
Evening (7 PM-10 PM)
Nighttime (10 PM-7 AM)
Approximate weighting
added to noise of single
event which occurs in
indicated period
Daytime 0 dB
Nighttime 12 dB
Daytime 0 dB
Evening 5 dB
Nighttime 10 dB
Number (N) of identical
events in time period
10 log N
10 log N
Summation of contributions
Logarithmic
Logarithmic
See Appendix C for additional details.
52
-------
a recent evolution of the CNR and is proposed as its successor by the FAA. It essentially
updates the CNR by substitution of the tone and duration-corrected effective perceived
13
noise level (EPNL) scale issued for aircraft certification, in lieu of the perceived noise
level (PNL) scale of the earlier CNR. Thus, the NEF accounts for both duration and
pure tone content of each single event sound, whereas the CNR accounted for neither.
37
The community noise equivalent level (CNEL) was recently introduced by the State of
38
California for monitoring purposes. It is based on the A-weighting to avoid the com-
plexity of the computer calculations required to obtain EPNL, and thus cannot contain a
pure tone weighting. It also differs from the NEF by inclusion of the evening time period
weighting, in addition to daytime and nighttime. However, despite these structural dif-
ferences, the difference between the absolute values of CNEL and NEF for specific
locations near airports is approximately constant at 35 -2 dB.
The CNEL has been applied to a series of community noise problems to
relate the normalized measured CNEL with the observed community reaction. The nor-
malization procedure followed the Rosenblith and Stevens method with a few minor modi-
fications. The correction factors added to the measured CNEL to obtain the normalized
CNEL are given in Table 11. Two examples of the application of these factors to the
measured values of the equivalent noise levels (L ) of the intruding noise are given in
eq
Table 12. The examples are drawn from the results at two locations in the range survey,
and illustrate an approximate procedure for calculating CNEL from the measured averages
of L in the daytime, evening and nighttime periods, accounting for both the period weight-
ings of 0, 5 and 10 dB, respectively, and their durations relative to a 24-hour day.
Values of normalized CNEL have been calculated for 55 case histories from
the literature and the files of Wyle Laboratories and Goodfriend-Ostergaard Associates.
The distribution of the cases among the various sources which impact areas of the commu-
nity are listed in Table 13 and the detailed data for each case are contained in Table 14.
The results are summarized in Figure 24, with an approximate NEF and CNR scale shown
for reference. The data are normalized to those descriptions in Table 11 for which the
correction is zero.
53
-------
Table 11
Corrections to be Added to the Measured Community Noise Equivalent Level (CNEL)
to Obtain Normalized CNEL
Type of
Correction
Description
Amount of Correction
to be Added to Measured
CNEL in dB
Seasonal
Correction
Summer (or year-round operation)
Winter only (or windows always closed)
0
-5
Correction
for Out-
door
Residual
Noise
Level
Quiet suburban or rural community (remote from large
cities and from industrial activity and trucking)
Normal suburban community (not located near indus-
trial activity)
Urban residential community (not immediately adjacent
to heavily traveled roads and industrial areas)
Noisy urban residential community (near relatively
busy roads or industrial areas)
Very noisy urban residential community
No prior experience with the intruding noise
Community has had some previous exposure to intruding
noise but little effort is being made to control the noise.
This correction may also be applied in a situation where
the community has not been exposed to the noise pre-
viously, but the people are aware that bona fide efforts
are being made to control the noise.
Community has had considerable previous exposure to
the intruding noise and the noise maker's relations with
the community are good
Community aware that operation causing noise is very
necessary and it will not continue indefinitely. This
correction can be applied for an operation of limited
duration and under emergency circumstances.
+ 10
+5
0
-5
-10
Correction
for Previous
Exposure &
Community
Attitudes
+5
0
™* v/
-10
Pure Tone
or Impulse
No pure tone or impulsive character
Pure tone or impulsive character present
+5
54
-------
Table 12
Two Examples of Calculation of Normalized Community Noise Equivalent Level
Factor
Energy Equivalent
Noise Level (Leq)
in dB(A) for Time Period
Duration and Time of Day
Correction Factor^
Subtotals Which are added
Logarithmically to Obtain
CNEL
Community Noise
Equivalent Level
Additional Corrections from
Table 11:
Seasonal
Residual Noise Level
Experience & Attitude
Pure Tone or Impulse
Total Additional Corrections
Normalized CNEL
Actual Reaction
Aircraft Landing Noise
in Noisy Urban /]\
Residential Community
Day
80
-3
77
Eve.
83
-4
79
Night
75
+6
81
84
0
-5
0
5
0
84
Extensive Lawsuits and
Political Pressure
Traffic Noise in Old
Residential Area Near
City Center C2)
Day
56
-3
53
Eve.
57
-4
53
Night
53
+6
59
61
0
0
-5
0
-5
56
No Reaction
(1) Location F in Figures 7 and 23
(2) Location L in Figures 7 and 23
(3) Duration correction is MO log -£r~ J where n is the number of hours in the period.
55
-------
Table 13
Number of Community Noise Reaction Cases as a Function
of Noise Source Type and Reaction Category
Type of Source
Transportation vehicles, including:
Aircraft operations
Local traffic
Freeway
Rail
Auto race track
Total Transportation
Other single-event or inter-
mittent operations, including
circuit breaker testing, target
shooting, rocket testing and
body shop
Steady state neighborhood
sources, including transformer
substations, residential
air conditioning
Steady state industrial opera-
tions, including blowers,
general manufacturing, chemical,
oil refineries, et cetera
Total Cases
Community Reaction Categories
Vigorous or
Threats of
.egal Action
6
1
2
9
5
1
7
22
Wide
Spread
Complaints
2
1
3
4
7
No Reaction
or Sporadic
Complaints
4
3
7
2
10
|
14
19
Total
Cases
12
3
1
1
2
19
7
24
55
56
-------
Table 14a
Summary of Data for 28 of the 55 Community Noise Reaction Cases
CASE NUMBER
CORRECTION FACTORS „
-D
-7
Z
NOISE SOURCE TYPE u
^ m •" uj " S
x > UQ ™ <3 N
g 8§^ it °2 |
Si Oo^Z o^iu«3 o-O Z
VIGOROUS REACTION
A-l
A-2
A-3
A -4
A-5
A-6
A-7
A-8
Rocket Testing 0 10 0 5 78
Wind Tunnel 0 5 5 0 80
Aircraft Landing 0-5 5 5 77
Aircraft Takeoff 0 5 0 0 76
Circuit Breaker Testing 0 0 0 5 78
Auto Roce Track 0 10 0 0 87
Aircraft Takeoff 0 5 5 5 84
Aircraft Landing 0-5 0 5 84
THREATS OF LEGAL ACTION
B-I
B-2
B-3
B-4
B-5
B-6
B-7
8-8
B-9
B-10
B-ll
B-12
B-13
B-14
Rocket Testing 0 10 0 5 72
Aircraft Ground Runup 0 5 -5 0 72
Wind Tunnel 0 5 0 5 71
Freeway 0-10 0 0 76
Aircraft Overflight 0 5 5 5 73
Plant Blower 0 0 5 5 77
Asphalt Quarry 0 10 0 0 74
Gloss Bead Plant Blower 0 10 0 5 77
Plastics Plant 0 0 0 5 71
Target Shooting Range 0 10 5 5 74
Residential Air Conditioning 0 5 5 10 77
Unloading Newsprint 0-10 0 5 71
Auto Body Shop -5 0 5 5 75
Motorcycle Roceway 0 0 5 5 75
WIDESPREAD COMPLAINT
C-l
C-2
C-3
C-4
C-5
C-6
Transformer Substation 0 10 0 5 64
Cement Plant 0-5 0 5 61
Aircraft Landing 0-5 5 5 67
Paperboard Plant Cyclone 0 10 0 5 65
Oil Refinery 0 0 0 0 64
Milling 4 Grinding Metal 0 5 0 0 71
(a) Data from Wyle files.
(b) Data from L. S. Goodfnend.
ADDITIONAL
=> CORRECTION
Z FACTORS
Si"
z oz
u Z _
B < S§ S,
o s 1 o> £
Z i- a Z _i ^
78 0 -24 81 a
82 10 0 83 c
76 5 -21 81 a
77 0 -16 76 a
78 0 -26 81 b
82 5 - 3 90 b
83 5 -24 84 o
86 10 -19 84 a
72 0 -24 75 a
72 0 -10 75 c
73 10 0 74 c
77 10 0 76 a
72 5 -11 76 o
78 10 0 80 b
74 0 0 77 b
78 10 0 80 b
72 10 0 74 b
74 0 - 3 77 b
78 10 - 3 80 b
72 10 0 75 b
75 0 - 7 79 a
70 5 - 3 84 a
65 10 0 67 a
61 0 0 64 a
66 5 -21 71 a
64 5 0 71 b
65 10 0 67 b
72 10 0 74 b
(c) Data from "Handbook of Acoustic Noise Control, Volume II. Noise
-------
Table 14 b
Summary of Data for 33 of the 55 Community Noise Reaction Cases
C£.
to
Z)
Z
5
CORRECTION FACTORS m
"O
~r
UJ
-7
NOISE SOURCE TYPE u
a > u S 7 ^ M
z o^^J z ^ 4 13 ^
O QQLO^^I— 2 ^
< ID <^ O Q°-< ^^ O
"•> o£ z £2 .« £o z
WIDESPREAD COMPLAINT ... continued
C-7
C-8
C-9
C-10
C-ll
C-12
C-13
C-14
Chemicol Plant Material Handling 0 0 0 5 63
Residential Air Conditioning 0 5 5 5 71
Transformer Substation 0 5 0 5 72
Rail Car Shaker 0 0 0 5 62
Transformer Substation 0 10 0 5 67
Positive Displacement Blower 0 0 0 5 60
Aircraft Takeoff 0 5 -5 5 68
Glass Manufacturing Plant 0 0 -5 0 62
SPORADIC COMPLAINTS
D-l
D-2
D-3
D-4
D-5
D-6
Factory Air Pump 0-10 0 0 61
Manufacturing Plant -5 0 0 5 58
Chemical Plant -5 5 0 0 56
Local Automobile Traffic 0 10 -5 0 61
Plastics Plant 0 10 0 0 61
Power Station 0-5 -5 0 59
NO OBSERVED REACTION
E-l
E-2
E-3
E-4
E-5
E-6
E-7
E-8
E-9
E-10
E-ll
E-12
E-13
Transformer Substation 0 10 -5 5 50
Aircraft Runup 0 5 0 0 51
Asphalt Tile Shaker 0-5 0 0 54
Asphalt Tile Reddler 0 0 0 10 50
Power Plant 0 10 0 0 57
Aircraft Overflight 0 5 -5 5 58
Aircraft Landing 0 0 -5 5 60
City Traffic 0 0-505]
Aircraft Log and Takeoff 0 0 0 0 57
Local Traffic 0 0 -5 0 54
Auto Assembly Plant 0 0-506]
Can Manufacturing 0-5-5 0 57
Oil Refinery 0-5-5 0 59
ADDITIONAL
^ CORRECTION
Z FACTORS
z o z
u z Z
a >- a 9
UJ < MJ O «
N S -7 N £ lj
i *r ^ uj U
^ O " *^ ' — ' Z
^ UJ <£ ^ — ' ^
O S 1 O > £
64 10 - 3 66 b
72 10 0 74 b
73 10 0 75 b
62 0 - 6 65 b
68 10 0 70 b
60 0 0 63 b
67 5 -24 68 a
63 10 0 65 b
61 0 0 64 c
59 10 0 61 a
57 10 0 59 a
61 0 -11 64 a
62 10 0 64 b
60 10 0 62 b
51 10 0 53 a
51 0 - 5 54 c
55 10 - 1 57 a
51 10 -10 53 a
58 10 0 60 b
57 0 -15 59 a
61 10 -17 63 a
50 5 -18 56 a
56 5 -17 61 a
54 0 -24 50 a
62 10 0 64 b
58 10 0 60 b
60 10 0 62 b
(a) Data from V/yle files.
(b) Data from L. S. Goodfriend.
(c) Data from "Handbook of Acoustic Noise Control, Volume II. Noise and Man," WADC Technical Report 52-204, Rosenb1 th, W.A., and
Stevens, K. N., June 1953.
58
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-------
The "no reaction" response in Figure 24 corresponds to a level which
ranges between 50 and 61 dB with a mean of 55 dB. This mean value is approximately
7 dB above the mean value assumed in categorizing the daytime residual noise (L0J
level for a "residential urban" community, which is the baseline category for the data
in the figure. This difference of 7 dB between the mean reaction line and Lc>_ is only
2 dB greater than the average difference between the outdoor median noise level (\-cr)
and the residual noise level, as shown in Table 3. Consequently, from these results
it appears that no community reaction to an intruding noise is expected on the average
when the normalized CNEL of the intruding noise is approximately equal to the daytime
outdoor median noise level (L,-n). This conclusion is not surprising; it simply suggests
that people tend to judge the magnitude of an intrusion with reference to the noise
environment which exists without the presence of the intruding noise source.
The data in Figure 24 indicate that widespread complaints may be expected
when the normalized value of CNEL exceeds the outdoor residual noise level by approxi-
mately 17 dB, and vigorous community reaction may be expected when the excess
approaches 33 dB. The standard deviation of these data is 3.3 dB and an envelope of
-5 dB encloses approximately 90 percent of the cases in Figure 24. Hence, this relation-
ship between the normalized CNEL and community reaction appears to be a reasonably
accurate and useful tool in assessing the probable reaction of a community to an intruding
noise and in obtaining one type of measure of the impact of an intruding noisie on a
community.
These community reaction data have also been used to test the effect of
the various normalizing factors in Table 11, together with the duration and time period
weighting factors in the CNEL, on the degree of correlation between the community
reaction and the normalized CNEL. The results, in Table 15, show that the duration is
the factor most necessary in the normalization to bring the data closer to a common line
and thus minimize the standard deviation. The absence of a duration correction increases
the standard deviation from 3.3 to 8.1 dB and would result in extending the bounding
envelope from -5 dB, as on the figure, to approximately - 12.4 dB. The next most
60
-------
Table 15
Effect of Normalizing Factors on 55 Community Noise Reaction Cases as
Measured by the Standard Deviation of the Data About the Mean
Relationship Between Community Reaction and Normalized CNEL
Factors* Included in
Normalizing Measured
Noise Level
All
AII7 except duration
Only
duration and time of
day correction in the
measured CNEL
AII7 except residual
noise level
All, except time of
day
AII7 except pure tone
and impulse
All, except experience
and attitude
AII7 except seasonal
Number of Cases
with Nonzero
Correction in
Deleted Factor(s)
—
28
1
35
38
32
23
3
Standard Deviation
in dB of all Cases
Except those Which
have Vigorous
Reaction or no
Reaction
2.9
7.5
7.1
6.2
4.6
3.7
3.4
2.9
Standard
Deviation
of all 55
Cases
3.3
8.1
7.5
6.4
4.6
4.3
4.0
3.3
* Factors are from Tables 10 and 11
61
-------
important factor is the residual noise level correction, lack of which increases the
standard deviation from 3.3 to 6.4 dB, a factor of almost two. Less important, but still
significant, are the corrections for time of day, pure tone/impulse, and prior experience/
attitude, the lack of which resulted in standard deviations of 4.6, 4.3 and 4.0, respec-
tively. No change occurred by removing the seasonal factor which was only applied in
three of the 55 cases.
The original Rosenblith and Stevens method computed the magnitude of the
noise by a quantity essentially proportional to L for the time period during which com-
munity reaction was caused. Thus, for a complaint against daytime noise, the reaction
would be compared against normalized L for daytime, whereas for a nighttime noise,
the reaction would be compared against the normalized L for the nighttime including
the+10 dB nighttime weighting factor. This procedure is slightly different from that
used in the CNEL which accounts for the contributions of all three periods in a single
number.
For comparison, the 55 cases have been plotted in Figure 25 using the
original procedure, except that the A-weighted equivalent level is used for the
magnitude of the noise. The results are generally similar to those of Figure 24,
although the standard deviation is 3.5 dB rather than 3.3 dB.
The data for the 55 cases were also compared with CNEL,, (see Appen-
dix C) which was obtained by replacing the day-evening-night corrections of the
standard CNEL with the day-night corrections of the NEF calculation procedure. The
resulting mean line was altered by less than I dB from that given in Figure 24 and the
standard deviation was only 0.1 dB greater than before, an insignificant difference.
Thus, these 55 cases can support either type of time period weighting for a single-
number measure of noise (CNEL or CNEL~) over a 24-hour period, or the original
period comparison concept, all in combination with the energy equivalent A-weighted
noise level and the other correction factors in Table 11, for the prediction of com-
munity reaction to noise pollution.
62
-------
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63
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5.2
Community Reaction and Annoyance
The normalized CNEL scale can also be compared with the results of social
surveys, such as those taken in London and in the USA. These surveys determine
community attitude by asking people what they think, rather than by assessing overt
reaction, as in the previous section.
Figure 26 shows that people are preponderantly in their homes when
40
they are annoyed by noise. Table 16, from an American survey, shows the acti-
vities disturbed as reported by people who were "extremely disturbed about aircraft
noise." As might be anticipated, problems related to speech intelligibility head the list.
Table 16
Activities Disturbed by Noise as Reported by
People who are "Extremely Disturbed by Aircraft Noise"
Activity
Percent
TV/Radio reception
Conversation
Telephone
Relaxing outside
Relaxing inside
Listening to records/tapes
Sleep
Reading
Eating
20.6
14.5
13.8
12.5
10.7
9.1
7.7
6.3
3.5
64
-------
0)
O)
0
•4—
(D
O
l_
0)
a.
80
70
60
50
40
30
20
10
0
I Inside
— At Home
Disturbed
from Time
to Time
Notice
but not
Disturbed
Do not
Notice
Figure 26. Percentage of People Who Were Ever Disturbed by Noise at
Home, Outdoors and at Work in London City Survey
65
-------
Figure 27 shows the average annoyance reaction found in the London Air-
39 36
port Survey as a function of CNR and approximate normalized CNEL. Figures 28
and 29 show the relationships of those who are "very much annoyed" and those "only a
little, or not annoyed" with data from the same survey. Also shown in Figure 28 is a
A Q
data point from a survey in Sweden, and a tangent line through the most important
range of community reaction.
These results demonstrate that a majority of the citizens are clearly very
much annoyed when the noise is sufficient to produce a normalized CNEL of 81 dB,
which would be expected to produce a vigorous community reaction in accordance with
the data in Figure 24. They also show that a small but significant percentage of the
population is still very much annoyed at the CNEL 55 value, where no community
reaction is expected. Thus, the true impact of the polluting effects of intrusive noises
as measured by annoyance goes deeper than indicated by the "no reaction" point.
5.3 Applicability of Noise Pollution Level and Traffic Noise Index to
Community Noise Assessment
Although the various versions of the community reaction correlation pro-
1 O A 7
cedure have found favor in this country and in international standardization, '
there are continuing efforts to develop new and better noise scales. Two of rhe most
22
recent efforts stemmed from a traffic noise and social survey by Griffiths and Langdon
in England in 1968. They assessed the dissatisfaction of residents at 11 sites with traffic
noise, and related the results to measured values of the noise. These measurements were
44
reported in terms of L,nr Lrn and Lnn; L values were reported later by Robinson.
r 10 50 90 eq '
The statistical values reported were the arithmetic averages of 24 samples (one per hour)
of 100 seconds duration each.
Griffiths and Langdon devised a traffic noise index which appeared to give
the best correlation between their 24-hour averages and the dissatisfaction scores. This
index is defined as:
TNI = L9Q + 4 (L10-L90) - SOindB (5-1)
66
-------
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Much-4.0
Moderate —
3.0
Little -
2.0
1.0
Not at All-
London Survey
39
I
80
L
90 100 110 120
Composite Noise Rating in dB
I I I I I I
130
50 60 70 80 90
Approximate Normalized Community Noise Equivalent Level in dB
Figure 27. Relationship Between Average Expression of Annoyance to Aircraft
Noise and the Composite Noise Rating, and with the Approximate
Scale for the Normalized Community Noise Equivalent Level
(After Ga|[oway36)
67
-------
"D
(U
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70
80 90 100 110
Composite Noise Rating in dB
120
I r I I
I
I I I
40 50 60 70 80
Approximate Normalized Community Noise Equivalent Level in dB
Figure 28. Percentage of People Expressing "Very Much Annoyed" as a
Function of Composite Noise Rating and with the Approximate Scale
for the Normalized Community Noise Equivalent Level
68
-------
80
<
"u
"o
Z
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8 <
a. =
60
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London Survey
39
I
I
70
I
80 90 100
Composite Noise Rating in dB
I I I I I
no
120
j
40 50 60 70 80
Approximate Normalized Community Noise Equivalent Level in dB
Figure 29. Percentage of People Expressing "Not At All" or "A Little" Annoyed
as a Function of Composite Noise Rating and with the Approximate Scale
for the Normalized Community Noise Equivalent Level
69
-------
Robinson reviewed the work of Griffiths and Langdon and proposed a quantity called
Noise Pollution Level, which accounted for both the equivalent energy of the noise and
44 45
the amount of its fluctuation in terms of its standard deviation (a). ' His primary definition
is:
NPL = L + 2.56 CT in dB (5-2)
e eq ;
However, in deriving the constants for NPL from the traffic noise study, he utilized
6
the approximate form of NPL:
NPL' = L + (L.n - L0J indB (5-3)
eq 1U rU
In addition, he proposed several other approximations which could be applied in appro-
priate situations, including the following expression which does not require direct com-
putation of L
eq
MDl _ ,
a "50
NPL = L,n + 2.56 a + a2/8.68 in dB (5-4)
Figure 30 compares TNI and NPL , calculated from the 24 average values
of 100-second samples, with the dissatisfaction scores at the 11 Griffiths and Langdon
sites. The correlation coefficient and standard deviation are approximately 0.88 and
3.9 dB, respectively, for TNI, and 0.82 and 3.2 dB for NPL . Figure 31 compares
L and (L - L-n) for these same data. This measure of (L - L^_) is similar to the
eq eq 90 eq 90
measures used in the correlation of community reaction in Figures 24 and 25. The cor-
relation coefficient and standard deviation are approximately 0.63 and 5.8 dB,
respectively, for L , and 0.76 and 1.9 dB for (L - LnJ.
eq eq VU
There are three principal observations which can be made from these com-
parisons. First, all measures except L (only) show reasonable correlation with the
eq
trend of the data, with TNI the best and NPL second best.
e
Second, the standard deviations for (L - L_A) are much smaller than
eq VU
those for TNI and NPL . This difference is the result of the difference in the decibel
e
ranges of the three scales, approximately 29 dB for TNI, 18.5 dB for NPL and 7.5 dB
70
-------
oo
Q
o
o
oo
c
o
a) TNI
22
70
75 80 85 90
Traffic Noise Index (TNI) in dB
95
O
u
1/1
_0
o
D
b) NPL
44
R = 0.823
a = 3.7 dB for Error in DS
- a = 3. 1 dB for Error in N PLe
- a = 3.2 dB for Error in NPLg
70
75 80 85 90
Noise Pollution Level (NPLe) in dB
95
Figure 30. Comparison of Griffiths and Langdon Dissatisfaction Score Data with (a) Traffic
Noise Index and (b) Noise Pollution Level. Regression Lines and Their Associated
Standard Deviations in Decibels are based on Assuming a 11 Error is in the Dissatisfaction
Score, Assuming all Error in the Index, or Level, and
Assuming Error is in both Measures
71
-------
o
u
to
c
o
o
D
a) L
eq
R = 0.627
a = 5.9 dB for Error in DS
Cr = 3.7 dB for Error In L
eq
a^ 5.8 dB for Error in DS&L
eq
55
60
65
70
75
80
85
Energy Average Noise Level (L ) in dB
o
u
to
c
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D
R = 0.764
a = 2.0 dB for Error in DS
'a = 1 .5 dB for Error in A
cr = 1.9 dB for Error in DS&A
10
15
20
25
30
35
Difference (A) Between Energy Average Noise Level (L a) and Log in dB
0 f\
Figure 31 . Comparison of Griffiths and Langdon Dissatisfaction Score Data/u with (a) Energy
Average Noise Level and (b) Difference Between Energy Average Noise Level and L9Q.
Regression Lines and Their Associated Standard Deviations in Decibels are Based on
Assumingall Error is in the Dissatisfaction Score, Assuming AM Error in the Level,
and Assuming Error is in both Measures.
72
-------
Third, the dynamic range of the basic L data is relatively small,
approximately 15 dB. Considering that the basic noise data were acquired in 100-second
samples, some random error, probably of the order of - 2 dB, may be expected in the
estimates of both L and L.n at the various sites. (For example, see Table 8 in
eq IU
Section 3.2.) In addition, the day-night variation may differ between the sites, as
seen in Figures 10 through 12, adding additional variability to the comparisons. Further,
there was undoubtedly some variation in level throughout the neighborhood at each site.
These probable errors in the measurement, plus the inherent errors in assessing the actual
dissatisfaction scores, are at least of the magnitude of the errors exhibited in the cor-
relations of the various scales. Therefore, it is difficult to conclude from these data
that any one of these three candidate scales is to be preferred.
The TNI and NPL were computed at each of the 18 locations in the noise
survey undertaken for this report. An example of the results is shown for the daytime
period in Figure 32, together with L and L)n, with all values plotted relative to L n.
eq IU VL/
For many of the locations, TNI is numerically similar to L , within approximately
-6 dB. However, at a few locations where intruding single event noises were sufficiently
numerous to effect L]n, the TNI is much greater than L , with a maximum difference of
almost 40 dB. In all cases, the NPL is greater than L .as would be expected from
e eq
Equation (5-2). The differences (NPL - L ) range between approximately 6 and
6 € C|
26 dB.
These data were also used to calculate the numerical differences among
the three methods for calculating NPL, which were given in Equations (5-2) through
(5-4). The results for the 18 locations are summarized in Table 17. The mean differences
and standard deviations for daytime are 3.8 and 3.7 dB, respectively, for (NPL - NPL )
and 1.4 and 1.3 dB, respectively, for (NPL - NPL'). In all periods, the standard
e
deviation using NPL' was less than that obtained using NPL , indicating that it is a
a
more consistent estimator of NPL .
e
73
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74
-------
Table 17
Relationships Among Various Methods of Calculating Noise Pollution
Level for Data from 18 Locations
Location
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
Mean Difference
Standard Deviation
NPLe*- NPLa*
Day
1.2
-0.1
1.8
1.2
1.5
10.3
2.8
2.3
3.5
3.2
9.5
2.7
4.4
4.2
1.4
1.2
2.5
14.4
3.8
3.7
Eve
1.3
1.8
1.7
0.7
1.8
10.6
2.1
1.7
4.1
1.8
7.4
3.3
8.8
2.7
2.0
0.4
Night
-1.6
3.0
1.2
2.2
1.6
15.6
1.5
3.3
4.2
4.0
8.7
2.5
5.8
2.5
6.1
-1.7
24 Hours
-0.7
2.2
1.7
-1.2
1.3
10.5
1.7
1.8
1.6
3.1
7.1
3.7
3.7
2.9
4.0
0.2
I
1.8
0
3.0
2.9
13.7
2.9
4.2
4.4
5.1
4.2
2.9
2.7
NPLe - NPL1*
Day
-0.7
2.5
0.9
-0.4
0.4
2.3
3.2
0.4
1.2
0.7
2.9
1.2
0
0.7
1.9
1.0
3.4
3.7
1.4
1.3
Eve
-0.7
-0.7
0.8
0.5
-0.1
3.5
0.5
0.7
1.9
0.8
2.4
0.9
1.7
0.8
0.3
2.6
0.2
2.7
0.9
1.2
Night
4.0
1.0
0.1
2.4
-0.3
7.8
1.9
1.4
9.7
3.4
3.8
4.0
7.0
2.3
2.8
9.9
4.2
3.6
3.8
2.9
24 Hours
3.8
6.5
1.7
6.2
1.6
7.4
6.8
2.8
7.0
3.1
7.9
2.7
6.9
3.7
5.6
5.2
3.7
0.4
4.6
2.2
NPLe = Leq +2.56 a
NPLQ = L50 + 2.56 a +a2/8.68
NPL1 =Leq+L10-L90
75
-------
Thus, NPL can be reasonably estimated for a wide variety of real out-
door noise environments by NPL1. This simplified approximation can be written as:
NPL' = (Leq - V + L,0
or (5-5)
(NPL' - L90> = (Leq - V + (L,0 - V
The computation for the daytime estimates of (NPL1 - L_n) can be visually made for the
data of Figure 32 by adding the (L... - Lgn) bar to the value of (L - Lgn)., The impli-
cation of this simplification is that NPL tends to count the magnitude of the intruding
noise twice — first in its contribution to L and second in its contribution to L rt.
eq 10
Thus, it might be expected that a correlation of community reaction, such as that
given for the 55 cases in Figures 24 and 25, would exhibit a wider data scatter than
obtained with (CNEL - L ), or (L - L ).
7\J ec| /u
An example of such an application of NPL was calculated for aircraft
flights over residential areas with differing residual noise levels. In all cases, the air-
craft noise was assumed to have a maximum level of 90 dB(A) and an effect! ve (energy
equivalent) duration of 5 seconds. The aircraft noise-time history was assumed to be
triangular. The community reaction for each case was estimated from Figure 24. The
results of this example are given in Figure 33. The left-hand side of the envelope of
cases is determined by the condition of 1 flight per hour. It shows no correlation
between NPL and community reaction, since the NPL varied only slightly although
(L - LQ_) varied significantly. The right-hand side of the envelope results from the
eq 7\j
condition of 30 flights per hour. Here, the NPL varied significantly with the reaction
scale. From this example, one might conclude that it would be difficult to obtain
good correlation between reaction and NPL, whenever the duration of the intruding
noise is only a small fraction of a given time period. Better correlation may be obtained
46
when more than one type of source is present;
on estimated rather than measured noise levels.
46
when more than one type of source is present; however in this case the results are based
76
-------
Community
Reaction
Vigorous
Several Threats
of Legal Action
Widespread
Complaints
Sporadic
Complaints
No Reaction
Assumed Residual
Noise Level
30 dB(A)
40 dB(A)
50 dB(A)
A 60 dB(A)
70
80
90
100
110
120
130
Noise Pollution Level in dB (NPL1 - Leq + L]Q -
Figure 33. Example of the Relationship Between Noise Pollution Level and Community
Reaction for Aircraft Noise, as a Function of Outdoor Residual Noise Level.
For the Outdoor Noise Level Without Aircraft Leq and L]Q were Assumed
to be 7 and 10 dB, Respectively, above the Residual Noise Level.
Calculations were made for 1,3, 10 and 30 Aircraft per Hour,
Each Having a Maximum Noise Level of 90 dB(A) and an
Effective Duration of 5 Seconds. Estimated Community
Reaction is Based on Figure 24
77
-------
A second example was calculated to see the effect of the steady-state
intruding noise which was turned on continuously, or for a fraction of the period under
consideration. Such source characteristics are common in industrial noise and air
conditioning hear exchangers. The example assumed that the residual noise; level was
40 dB(A) and the intruding noise was 60 dB(A). Both NPL and NPL1 were calculated.
e
together with L of the intruding noise and L of the intruding noise plus the noise
a eq eq r
which was assumed to exist without the presence of the intruding noise.
The results are presented in Figure 34. When intruding noise is con-
tinuous ("on time" fraction of 1.0), NPL = NPL' = L = 60 dB. However, when
e eq
the source is only on for 50 percent of the time, NPL has a maximum of 82.6 dB,
22.6 dB greater than when the source is on all the time. In fact, the NPL exceeds
60 dB for all on-time fractions between approximately 0.04 and 1.0. In this example,
NPL' is a poor estimator of NPL , particularly when the "on time" fraction exceeds
0.1. The reason is that for this steady-state noise, L._ = L__ for all values of the
"on time" fraction which exceed 0.1. Consequently, for intermittent steady-state
noise, unlike the fluctuating noises of Figures 32 and 33, NPL' is not an appropriate
estimator of NPL .
e
The results of the discussions in this section indicate that NPL is less
suitable than (L - L__) for use in measuring the magnitude of intruding noises relative
to residual noises, with respect to their effects on people. This conclusion is par-
ticularly relevent to intermittent single-event high-level noises with short duration,
as well as intermittent steady-state noises which have "on time" fractions between
0.1 and 0.9.
78
-------
90
80
70
CO
-a
60
50
40
NPL
Leq +2. 56 a
NPL' = Leq+L10-L90
Where L includes the combination
of intruding noise with outdoor noise
from other sources
\
NPL
.X^^NP,
-—•*" I
"" L (combined) J .
L (Intruding Noise)
ec\
. I
0.01 0.02
0.05 0.1
0.2
0.5
Noise on Time FracHon
.0
Figure 34. Example of the Effect of Turning on a Steady State
Intruding Noise of 60 dB(A) on Noise Pollution Level as a
Function of the "On Time" Fraction. The Outdoor Noise
Without the Intruding Noise is Specified by
LIQ = 50 dB(A), Leq = 47 dB(A) and
L90=40dB(A)
79
-------
6.0 THE GROWTH OF NOISE POLLUTION
There has been considerable public discussion about the growth of noise
pollution. Some of this discussion has led to dire predictions that the noise in our
environment is increasing by as much as 1 dB per year, or 10 dB per decade. Clearly,
such a growth rate, if true, would lead to very severe consequences. To place this
problem in perspective, it is useful to examine the possible changes in both the
intruding noises and the residual noises over the past few decades.
6.1 Change in Intruding Noises
There has been considerable growth in the number of miles of urban free-
ways and thru ways since 1950. This growth is accompanied by an increase in noise in
neighborhoods adjacent to the freeways. Similarly, there has been a significant
23
increase in commercial air travel since 1950. This increase, together with an increase
of the noise level of the jet aircraft relative to the older propeller aircraft,r and the
building of homes around existing civil airports has resulted in a significant number of
noise problems.
The amount of land estimated to lie within the CNEL 65 dB contours is
illustrated in Figure 35 for both freeways and airports. These estimates ^ show that
approximately 2000 square miles of land are bounded by CNEL 65. The actual land
use within these impact boundaries (airport property and freeway property have been
excluded) is not known. However, if it is assumed that the average use is like the
average urban land use, approximately 10 million people would be expected to live
in these areas.
These estimates of the impacted area are rather conservative since an
intruding noise source which causes a normalized CNEL of 65 dB in an urban residential
community is expected to result in widespread complaints. Consequently, the impact
of noise pollution extends beyond the CNEL 65 dB boundary, even in an urban residen-
tial community. In addition, for suburban communities which have lower residual noise
levels, a CNEL of 55 or 60 dB is equivalent to a CNEL of 65 dB in a residential area.
Hence, the estimates in Figure 35 are even more conservative.
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1970
1965
o
0)
1960
1955
Legend
Total
Aircraft
Urban Freeways
500 1000 1500
Number of Square Miles
2000
2500
Figure 35. Approximate Growth in Aircraft and Freeway Noise Impacted Land
Area Enclosed by Community Noise Equivalent Noise Level of 65 dB.
Area for These Two Sources was Very Small Prior to 1955
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In addition, the growth of construction activity within the city and
industrial plants in the suburbs and rural areas bring increased noise pollution to each
affected area. Further, as illustrated in Figure 36, the number of noisy devices such
as power lawnmowers and motorcycles has increased from a few hundred thousand units
in 1950 to over 20 million in 1970, bringing additional single event noise pollution
to the urban and suburban residential areas. Similarly, the introduction and use of
recreational vehicles, chain saws, and fully-equipped campers has introduced a new
element of noise pollution to the wilderness areas. Even at a remote location on the
north rim of the Grand Canyon, the noise from a small propeller-driven private aircraft
had a maximum level of 70 dB(A), a 54 dB increase above the daytime residual noise
level of approximately 16 dB(A).
The increasing number of sources which produce high noise levels
gives clear evidence of the significant growth of noise pollution from intruding sources
over the last two decades. Although the majority of this growth occurred in specific
areas where freeways or airways were located adjacent to the communities, a significant
number of new single event sources were added to all areas from the wilderness to the
inhabited suburban and urban residential communities.
6.2 Change in Residual Noise
The question remains whether these additional intrusive noises, together
with any changes in the noise characteristics of all other sources, have changed the
outdoor residual noise levels in the residential areas which have not had a significant
land usage change. It is very difficult to answer this question without the existence
of a statistically significant survey of the noise environment in residential areas within
the United States, either current or past.
To obtain a "current" estimate, the data for the 11 residential locations
in the range survey, Table 3 of Section 3.1, have been combined with data from 17
19
typical residential locations from another recent survey to give a better composite
picture of an "average" urban residential noise environment. The separate and combined
data from these two surveys, given in Table 18, indicate that both are from similar
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1970
o I960
1950
0
Legend:
Gas Powered Lawnmowers
Motorboats
Motorcycles
jj Chain Saws
10
Number of Units
(in millions)
20
Figure 3 6 . Approximate Growth of a Few Types of Noisy Recreational
Vehicles and Outdoor Home Equipment. There were Negligibly
Few Gas Powered Lawnmowers, Chain Saws
and Snowmobiles in 1950
83
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Table 18
Residual Noise Levels (190) in dB(A) for 28 Residential Locations
Including 11 from this Survey and 17 Locations From
Measurements in Los Angeles, Detroit and Boston''
Period
Day
Evening
Night
Quantity
L90
Std. Dev.
L90
Std . Dev .
L90
Std. Dev.
1 1 Locations
45.6
4.6
46.7
4.1
39.8
4.1
17 Locations
47.5
5.8
44.9
5.6
37.8
6.2
Combined
28 Locations
46.7
5.3
45.6
5.0
38.9
5.3
populations, particularly in the daytime. However, since neither survey was undertaken
with the intent of statistically sampling a city and there are only 28 locations in total,
the results should only be considered indicative of central trends. The "past" data which
are available consist of the results of four surveys. ' These surveys cover the last
34 years, beginning with the extensive Bell Telephone Company survey of noise in 1937 in
residential areas in Chicago, Cleveland and Philadelphia. The comparison of the daytime
residual noise data from five surveys is given in Figure 37.
Each survey was different in method, objective and instrumentation, and
none compare identical locations. Most were also different in methods of reducing and
reporting data as well. Therefore, it was necessary to adjust the data to a common base
for comparison. The data for the 1937 and 1968 surveys were published in terms of the
median outdoor noise level (\-^Q), and those of the 1957 survey in terms of an energy mean
of the noise environment. All three results have been corrected to the residual noise
level (Lpo) by subtracting the average difference of 5 dB found between the median and
residual levels in the current data. The mean and 50 percent range for the residual noise
levels of the 1947-8 and 1971 surveys are shown as originally presented.
84
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Range of 50% of Data v /- Mean
1937 Chicago, Cleveland
& Philadelphia (several
hundred areas)'^
Range of 90% of Data
1947 Chicago (more than
-1948 100 areas) 15
1954 Within 12 miles of
8 Airports in Eastern
USA (180 areas)16
Atlantic States -^-
1968 Suburban Areas in
Atlantic St<
(9 areas)18
1971 Los Angeles, Boston
and Detroit (28 areas)
Average of Urban and
Suburban, not including-the
1954 data
Calculated Urban and _ _
Suburban with Equal _ Y///M//A
Weighting on each of 1 - 1 - 1
the Four Categories
j
Y////X///\
I
i
M
1
20 30 40 50 60
A-Weighted Residual Noise Level (L ) in dB re 20 uN/m2
Figure 37. Comparison of Five Surveys of Outdoor Noise Levels in Residential Areas in
the United States Between 1937 and 1971. The Data for 1937, 1954 and 1968
Have Been Corrected from Their Published Values to an Approximate
Residual Noise Level by Subtracting 5 dB to Account for the
Difference Between the Median and Residual Noise Levels
85
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Disregarding the 1954 results, the means of the other four surveys lie
between 46 and 50 dB(A) with a grand average of 46.9 dB(A). This value is also close
to the average value of 45.5 dB(A) calculated for the suburban categories of quiet and
normal suburban, and urban and noisy urban residential areas described in Table 5 of
Section 3.1.
The mean value of the 1954 data is 7.7 dB below the 1971 results and
7.9 dB below the average of the other four surveys. This survey was designed to inves-
tigate the effect of aircraft noise at many locations under aircraft flight tracks up to
12 miles from each of eight airports, and included rural as well as suburban and urban
locations. It is probable that the principal reason for the low values reported by the
1954 survey is that its mix of locations gave significantly more weight to the quiet
rural and suburban areas than to the urban and noisy urban residential areas. Similarly,
the 1937 survey included city apartment dwellings as well as suburban and urban resi-
dential areas with detached dwellings. This difference in emphasis probably resulted
in higher emphasis on the "very noisy urban residential" category and explains why these
data have the highest reported mean value for the residual noise level.
Thus, it is considered that the 1937 survey was biased to slightly noisier
areas, the 1954 survey was significantly biased to the quieter areas, and the three
remaining surveys are probably somewhat similar in their distribution of locations among
the categories of Table 5. With this perspective, it is concluded that where land use
has not changed, there is no strong trend toward an increase in the average suburban
and urban residential area residual noise levels over the past 34 years. Further, it
appears that the only increase which can be inferred from these data is 2 dB in over
two decades based on the difference between the 1947-8 and 1971 results.
This conclusion is also supported by a comparison of the noise at two
locations in Los Angeles, where the 1971 data are directly comparable to measurements
made in 1955 and 1959. At a normal suburban neighborhood location, where no signi-
ficant change in land or road use has occurred over 16 years, the two measurements of
the residual noise level agreed within 1 dB between 1955 and 1971. In the other case,
86
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the 1971 measurements in a residential urban area were approximately 2 dB higher than
in 1959, due at least in part to the activation of a new major freeway within 2/3
mile of the location.
Table 19 presents a comparison of residual noise levels in the downtown
city. The results for New York, Chicago and London from 1937-1962 show remarkable
agreement. However, again direct comparisons at the same location are not available,
and the only inference to be drawn is that no significant increases in level are demon-
strated for these extremely noisy locations.
Table 19
Comparison of Outdoor Daytime Residual Noise Levels
in the Downtown City
City
New York*
Business District14
Chicago -
Heavy Traffic15
London20
Ottawa21
Los Angeles
(Current survey)
Number of
Locations
Large
Large
Approximately
20
One
One
Year
1937
1947-48
1961-62
1968
1971
Daytime Residual
Noise Level dB(A)
Range
62 to 75
63 to 73
—
—
Average
68
68
68
68
73
*
Original data which approximated median noise level (L^Q) corrected to
Residual Noise Level by subtracting 5 dB.
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The basic conclusion from all of these comparisons is that the average
outdoor residual noise level has probably changed only a small amount over the past
few decades, in an area which has had a constant land usage throughout the period.
However, if the land use has changed at any location, such as from rural to suburban,
from suburban to urban, or urban to downtown city, the outdoor residual noise level
probably increased significantly (10 dB or more), approximately in accordance with the
values in Table 5. Consequently, even if the residual noise level fora given category
of neighborhood has not changed, the sprawl of the cities and the suburban expansion
during the post war period has significantly increased the number of people impacted
by urban noise. In addition, at many locations, the outdoor energy equivalent and
maximum noise levels has increased significantly because of the addition of new
intruding noise sources, such as an electric power plant, a freeway, or a jet aircraft
overflight path.
Thus, in summary, the growth of noise pollution is principally associated
with the spread of areas characterized by high noise levels, the growth in numbers of
noisy devices used for recreation and labor saving, and the construction of freeways
and increase in use of airways by noisy aircraft near residential communities.
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7.0 CONCLUSIONS AND RECOMMENDATIONS
The data and discussions in this section lead to several significant
conclusions and recommendations regarding the nature of noise pollution and the
methods of measuring its magnitude. Although many of these conclusions must be
regarded as tentative, because of the lack of a statistically sound community noise
baseline, the general trends appear straightforward and give useful perspective for
the overall nature of the problem.
7.1 Conclusions
The principal conclusions are:
Range of Outdoor Environments
• The outdoor daytime residual noise level in a wilderness, such as
the Grand Canyon rim, is of the order of 16 dB(A), on the farm
it is of the order of 30 to 35 dB(A), and in the city it is of the
order of 60 to 75 dB(A). These increases in noise level, from
wilderness to farm and to city, are the result of man's activities
and his use of machines.
• Significant errors may be expected in the measurement of outdoor
noise levels in environments characterized by single event noise
intrusions, unless the duration of the measurement samples is
sufficiently long.
• The mean (arithmetic average) and median (L^n) data obtained
at the 18 locations in this survey were generally within one dB
of each other, with a standard deviation of 0.8 dB. Therefore,
the arithmetic average of many sequential measurements, as read
on a sound level meter, should be a good estimate of the statis-
tical median (I-5Q).
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• The residual noise level read on a graphic level recorder for the
data in this survey was found to be about 1 dB less than Log
and one dB greater than 199, both with a standard deviation of
approximately 2 dB.
• The maximum noise level measured in an hour was found to be
significantly higher than both LJQ and LI at almost all locations.
Intruding Noises
• Areas in which the daytime outdoor median noise level exceeds
the range of 56 to 60 dB(A), categorized as "very noisy urban",
are not well suited to detached residential housing, since normal
voice conversation outdoors is limited to distances of less than
6 to 10 feet between talker and listener. Also, when the noise
level is above this range, it is not possible to have relaxed con-
versation in a living room at a distance of 10 feet with windows
or sliding glass doors fully opened.
• Areas in which the daytime outdoor median level exceeds 66 dB(A)
are not suited to apartment living unless the buildings are air-
conditioned so that the windows may be kept closed to enable
relaxed conversation indoors. If the outdoor median noise levels
are above 71 dB(A), special soundproofing is necessary to preserve
the indoor noise environment, even with windows closed.
• The outdoor residual noise level in a suburban and urban resi-
dential communities serves the useful function of providing speech
privacy between neighbors. Therefore, the requirements for speech
privacy should be considered in determining the lower limit of a
desirable residual noise level in each type of community.
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• Maxfmum nofse levels below 72 dB(A) for individual single events
have been judged acceptable in one series of subjective tests,
which is consistent with the apparent general acceptability of
maximum levels of 62 - 70 dB(A) resulting from normal operation
of a standard passenger automobile on a residential street.
Community Reaction to Noise Intrusion
• The correlation of community reaction with the Community Nofse
Equivalent Level (CNEL) normalized by the method of Rosenblith
and Stevens, appears to give reasonable predictions of community
complaints to noise intrusion, with 90 percent of the data within
+ 5 dB of the mean relationship between the normalized magnitude
of the intruding noise and the degree of community reaction.
• The data indicate that no reaction should be expected to occur
when the normalized CNEL of the intruding noise is less than
2 dB above the daytime median noise level, or equivalently,
approximately 7 dB above the residual noise level. However,
some social surveys indicate that when the intruding noise equals
this level, approximately 20 percent of the population is "very
much annoyed," although 45 percent are only "a little," or
"not at all annoyed."
• The significant complaint reactions from the 55 community reaction
cases and the approximate percentage of the population "very much
annoyed" and "only a little." or "not at all annoyed" from the
London study are given in Table 20.
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Table 20
Summary of Expected Community Reaction and Approximate Annoyance
as a Function of Normalized Community Noise Equivalent Level
Expected
Community
Reaction
No reaction
Sporadic complaints
Widespread complaints
Threats of legal action
Vigorous action
Approximate Difference Between
Normalized CNEL and Average
Daytime Residual Noise Level
(L90) in dB
Mean
7
11
17
26
33
Range of Data
2 to 13
8 to 13
12 to 24
23 to 29
28 to 39
Approximate
Percent
Very Much
Annoyed
20
26
37
60
~ P7
~ O/
Approximate
Percent
Little or Not
Annoyed
45
37
26
14
~ 7
~ /
• To measure the magnitude of intruding noises, relative
to community reaction. Noise Pollution Level was found
to be less suitable than a quantity equal to the difference
between the energy equivalent noise level (Leq) and L$IQ.
Growth of Noise Pollution
• The limited available data from community noise surveys conducted
over the past 34 years indicate that little increase has occurred in
the residual noise level, except where land usage has changed.
Where such change has occurred, the noise has generally increased,
probably in accordance with the expected change between land
use categories in Table 5, such as plus 10 dB from rural to suburban,
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or plus 20 dB from rural to noisy urban. A significant spread of
noise pollution has occurred in this manner because of the large
growth of the urban and suburban areas, and their populations,
in the last 20 to 30 years.
A significant increase of noise pollution in the past 20 years has
resulted from the rapid growth of commercial aviation and from its
use of jet aircraft which are about ]0 to 20 dB noisier than the
piston engined aircraft that were replaced. A somewhat lesser,
but still significant, increase of noise pollution has resulted from
the construction and use of freeways which are located within
urban and suburban residential areas. It is estimated that at least
2000 square miles of urban and suburban areas have been severely
impacted by noise from these two major sources, with lesser degree
of impact extending over a much larger area.
The rapid increase in popularity and use of noisy recreational
vehicles and home lawn care equipment powered by poorly muffled
internal combustion engines has contributed to noise pollution in
both the wilderness and the residential neighborhood.
7.2 Recommendations
Noise pollution in the community is an extremely complex problem,
caused by a variety of sources, and measured in terms of its differing
effects on people. To approach this problem requires a systematic
approach to the measurement and prediction of community noise,
establishment of noise quality goals, control of the basic noise
characteristics of the various important sources, community planning
for and regulation of noise, and continued research to better understand
the effects of noise on people and to improve noise control technology.
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The following recommendations address part of this overall problem:
Measurement, Prediction and Goals
• Accomplish a nationwide community noise survey with sufficient
locations to have statistical significance to obtain:
1. National community noise baseline.
2. Opinions of the noise environment for each location.
3. Definition of speech privacy requirements.
4. Definition of minimum requirements and procedures for
noise monitoring systems.
5. Data input to noise quality goals.
6. Data for improving prediction model for community noise.
• Plan and conduct one or more metropolitan areawide monitoring
demonstration programs to obtain total effect of aircraft and free-
way noise in residential areas and to further refine monitoring
methods and techniques.
• Review and update existing analytical methods for predicting
outdoor noise levels in the community from transportation sources,
including obtaining any necessary physical data on attenuation.
• Establish noise quality goals for the indoor and outdoor environment,
covering both constant and intermittent single or multiple-event
noise .
Control of Basic Source Noise, Community Planning and Regulation
• Establish source noise standards and goals, consistent with the
community noise quality goals for all major source categories,
including all transportation and recreational vehicles, construction
equipment, lawn care equipment, and air conditioning equipment.
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Establish noise labeling procedures for all consumer products
which produce noise.
Develop guidelines for achieving acceptable freeway and highway
noise levels, incorporating the effects of source noise reduction,
barriers, and other design elements.
Develop a model noise ordinance for use by cities and towns.
Develop model building codes which include noise performance
criteria.
Define aircraft noise goals which are compatible with the community
and the future air transportation system.
Research
Work with appropriate federal agencies to support research funding
to develop the technology for quieter aircraft and their operation.
Conduct research to improve understanding of effects of noise
on people:
1. Correlate health records versus noise exposure around major
metropolitan airports.
2. Perform experiments in sleep disturbance to determine
importance of community noise in sleep disturbance with
attention to characteristics and number of noise events versus
steady state background.
3. Obtain better definition of the role of short-time single-event
noise interruption in speech and telephone conversation, and
TV and radio listening.
4. Ascertain the relative importance of indoor and outdoor
environment on community and individual reaction to noise.
95
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5. Determine noise criteria for people in outdoor area:; such
as parks.
Conduct demonstration programs in residential housing to find
relationship between room noise reduction and human reaction
to develop better criteria for building wall transmission loss, and
to provide design goals for reduction of traffic noise for
buildings near major freeways.
Conduct research towards quieting city street canyons through
development and application of outdoor acoustical absorbing
material to building exterior surfaces.
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1. "Report to the President and Congress on Noise, " U.S. Environmental Protection
Agency, December 31, 1971.
2. Young, R.W., "Measurement of Noise Level and Exposure," p. 45, Transpor-
tation Noises, University of Washington Press, 1970.
3. "American National Standard Specification for Sound Level Meters,"
ANSI SI.4-1971, American National Standards Institute, Inc.
4. Fletcher, H. and Munson, W.A.,"Loudness, Its Definition, Measurement and Cal-
culation," I. II. Audio 41, 40, 53, 1957.
5. Stevens, S.S., "The Calculations of the Loudness of Complex Noise," J. Acoust.
Soc. Am., 29, 603-606, 1957.
6. Stevens, S.S., "Procedure for Calculating Loudness: Mark VI," J. Acoust. Soc.
Am., 33, 1577-1585, 1961.
7. Stevens, S.S., "Assessment of Noise: Calculation Procedure Mark VII," Paper
355-128. Laboratory of Psychophysics, Harvard University, Cambridge, Mass.,
December 1969.
8. Zwicker, E.,"Ein Verfahren zur Berechnung der Lautstarke. (A Means for Cal-
culating Loudness.)"Acoustica 10, 304, 1960.
9. Kryter, Karl D., "Perceived Noisiness (Annoyance)," p.269, The Effects of
Noise on Man, Academic Press, 1970
10. Young, R.W., and Peterson, A., "On Estimating Noisiness of Aircraft Sounds,"
J. Acoust. Soc. Am., 45, 834-838, 1969.
II. Ollerhead, J.B., "An Evaluation of Methods for Scaling Aircraft Noise Per-
ception," Wyle Laboratories Research Staff Report WR 70-17, Contract
NAS1-9257, May 1971.
12. "Procedure for Describing Aircraft Noise Around an Airport," ISO Recommendation
R 507, International Organization for Standardization, June 1970.
13. Federal Aviation Regulations, Part 36, "Noise Standards: Aircraft Type Certi-
fication," November 1969.
97
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14. Seacord, D.F., "Room Noise at Subscribers' Telephone Locations," J. Acoust.
Soc. Am., 12, 183-187, July 1940.
15. Bonvallet, G.L., "Levels and Spectra of Traffic, Industrial and Residential Area
Noise," J. Acoust. Soc. Am., 23, 435-439, July 1951.
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Near Airports," NACA Technical Note 3379, December 1954.
17. Veneklasen, P.S., "City Noise- Los Angeles," Noise Control, July 1956.
18. Donley, Ray, "Community Noise Regulation," Sound nnd Vibration Magazine,
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19. Simpson, Myles and Biship, Dwight, "Community Noise Measurements in
Los Angeles, Detroit and Boston," Bolt Beranek and Newman Report No. 2078,
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20. "Noise in Towns," NOISE, Chapter IV, 22-31, Presented to Parliament by the
Lord President of the Council and Minister for Science by Committee on the
Problem of Noise, July 1963; Her Majesty's Stationery Office, Reprinted 1966.
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National Research Council of Canada, Ottawa, 1970.
22. Griffiths, I.D. and Langdon, F.J., J. Sound and Vib. 8, 16, 1968.
23. Wyle Laboratories Research Staff, "Noise from Transportation Systems, Recreation
Vehicles and Devices Powered by Small Internal Combustion Engines," WR 71-17,
Office of Noise Abatement and Control, Environmental Protection Agency,
Washington, D.C., November 1971.
24. Webster, J.C., "SIL- Past, Present and Future," Sound and Vibration Magazine,
August 1969.
25. Beranek, L.L., Acoustics, McGraw-Hill Electrical and Electronic Engineering
Series, McGraw-Hill Book Co., Inc., 1954.
26. Kryter, K.D., "Speech Communication in Noise," AFCRC-TR-54-52, Air Force
Cambridge Research Center, Air Research and Development Command, Boiling
Air Force Base, Washington, D.C., May 1955.
27. "American National Standard Methods for the Calculation of the Articulation
Index," ANSI S3.5-1969, American National Standards Institute, Inc.
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28. Mills> C.H.G. and Robinson, D.W., "The Subjective Rating of Motor Vehicle
Noise," Appendix IX, NOISE, Presented to Parliament by the Lord President of
the Council and Minister for Science by Committee on the Problem of Noise,
July 1963; Her Majesty's Stationery Office, Reprinted 1966.
29. "Selection of a Unit for Specification of Motor Vehicle Noise," Appendix A,
Urban Highway Noise: Measurement, Simulation and Mixed Reactions,
Bolt Be ran ek and Newman Report 1505, April 1967.
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Inc., "Handbook of Acoustic Noise Control, Vol 2, Noise and Man," WADC
TR-52-204, Wright-Patterson Air Force Base, Ohio: Wright Air Development
Center, 1953.
31. Stevens, K.N., Rosenblith, W.A., and Bolt, R.H., "A Community's Reaction to
Noise: Can It Be Forecast?" Noise Control, I, 63-71, 1955.
32. Stevens, K.N., and Baruch, J.J., "Community Noise and City Planning,"
Handbook of Noise Control,Chapter 35, McGraw-Hill Book Co., 1957.
33. Parrack, H.O., "Community Reaction to Noise," Handbook of Noise Control,
Chapter 36, McGraw-Hill Book Co., 1957.
34. Stevens, K.N. and Pietrasanta, A.C., and the Staff of Bolt Beranek and Newman,
Inc., "Procedures for Estimating Noise Exposure and Resulting Community Reactions
from Air Base Operations," WADC TN-57-10, Wright-Patterson Air Force Base,
Ohio: Wright Air Development Center, 1957.
35. Galloway, W.J. and Pietrasanta, A.C., "Land Use Planning Relating to Air-
craft Noise," Technical Report No. 821, Bolt Beranek and Newman, Inc.,
Published by the FAA, October 1964. Also published by the Department of
Defense as AFM 86-5, TM 5-365, NAVDOCKS P-98, "Land Use Planning with
Respect to Aircraft Noise."
36. Galloway, W.J., and Bishop, D.E., "Noise Exposure Forecasts: Evolution,
Evaluation, Extensions, and Land Use Interpretations," FAA-NO-70-9,
August 1970.
37. Wyle Laboratories Research Staff, "Supporting Information for the Adopted Noise
Regulations for California Airports," WCR 70-3(R) Final Report to the California
Department of Aeronautics, January 1971.
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No. 48-11-28-70. Subchapter 6. Noise Standards.
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39. "Social Survey in the Vicinity of London (Heathrow) Airport, Appendix XI,
NOISE, Presented to Parliament by the Lord President of the Council and Minister
for Science by Committee on the Problem of Noise, July 1963; Her Majesty's
Stationery Office, Reprinted 1966.
40. "Community Reaction to Airport Noise— Final Report," Volume I, Tracer Docu-
ment No. T-70-AU-7454-U, September 1970.
41. Borsky, P.N., "Community Reactions to Air Force Noise," WADD Technical
Report 60-689, Parts 1 and 2, Wright-Patterson AFB, Ohio, March 1961.
42. Galloway, W.J., and Von Gierke, H.E., "Individual and Community Reaction
to Aircraft Noise: Present Status and Standardization Efforts," International
Conference on the Reduction of Noise and Disturbance Caused by Civil Aircraft,
London, November 1966.
43. Private Communication: To - Mrs. Elizabeth Cuadra, Wyle Laboratories, From -
Mr. Erland Jonsson, National Institute of Public Health, Stockholm, Sweden,
re: Summary of Swedish Study of Reactions to Aircraft Noise Made in 1959.
Communication dated February 20, 1970.
44. Robinson, D.W., "The Concept of Noise Pollution Level," National Physical
Laboratory, Aerodynamics Division, NPL Aero Report Ac 38, March 1969.
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Vibration, 14 (3), p. 279-298, 1971.
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Response," No. 1996, November 1969.
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APPENDIX A
COMMUNITY NOISE SURVEY
This appendix provides site descriptions, noise data and measurement procedures
relating to each of the 18 noise survey locations. Table A-l provides the letter
designations and titles for all locations.
A.I Descriptive Figures
The descriptive information and data for each location are contained in
a series of three consecutive figures. The figures A-la, A-lb, and A-lc all relate
to Location A. Figures A-2a, A-2b, A-2c relate to Location B. Those designations
continue through Location R, depicted in Figures A-18a, A-18b, and A-18c. The
content of these figures is described in the following paragraphs.
A. 1.1 Site Descriptions
Figures A-la, A-2a, through A-18a describe the type of community
represented by the survey site and its geographical location. Each figure contains
a local street map, a photograph of the location, a description of the local noise
environment, and pertinent comments on microphone location and the measured data.
The survey location is indicated on each street map by a black diamond ($).
A. 1.2 24-Hour Time History Records
Figures A-lb, A-2b, through A-18b are 24-hour time history records
of A-weighted noise levels for each survey location. These records are portrayed on
two facing pages; the first page depicts noise levels for 0000 hours to 1200 hours and
the second page depicts noise levels for 1200 hours to 2400 hours.
Data ranging in length from several seconds to several minutes is missing
from the 24-hour time history records for some of the survey locations because the
recorder was temporarily stopped for system maintenance or adjustment.
During the 24-hour measurements at Locations F and J, the community
noise levels occasionally dropped below the noise threshold of the measurement
A-l
-------
instrumentation. This is indicated by the fairly constant level on the 24-hour
recording. This condition also occurred at Location R and is discussed in Figure 18-A.
At Locations B, M and O, portions of the 24-hour record which appear to have reached
a threshold are actually indicating a constant noise level established by air conditioning
systems, blowers, or other continuous local noise sources.
A. 1.3 24-Hour Outdoor Noise Summaries
Figures A-lc, A-2c, through A-18c are summaries of the 24-hour outdoor
noise levels at each location. These figures provide a statistical portrayal of community
noise throughout a 24-hour period. The upper graphs (a) give the maximum and residual
noise levels read from a graphic level recorder, together with the hourly and period
values of the levels which are exceeded 99, 90, 50, 10, and 1 percent of the time
(Lp0/ Lgn, L,.-, L,n, and L,), respectively, and the energy mean equivalent level (L ).
The lower graph illustrates the statistical distribution of the noise levels throughout
each of the three time periods.
A-2
-------
TABLE A-1
Community Noise Survey Locations
Location Page Address
A A-5 Third Floor Apartment, next to Freeway —
West Los Angeles, California
B A-9 Third Floor Downtown Hi-Rise —
Los Angeles, California
C A-13 Second Floor Tenement — Harlem, New York
D A-17 Urban Shopping Center — Torrance, California
E A-21 Popular Beach on Pacific Ocean —
Corona Del Mar, California
F A-25 Urban Residential Near Major Airport —
Lennox, California
G A-29 Urban Residential Near Ocean -
Redondo Beach, California
H A-33 Urban Residential, 6 miles to Major Airport —
Los Angeles, California
I A-37 Suburban Residential near R/R tracks —
Simi Valley, California
J A-41 Urban Residential — Inglewood, California
K A-45 Urban Residential near small Airport —
Newport Beach, California
L A-49 Old Residential near City Center-
Los Angeles, California
M A-53 Suburban Residential at City Outskirts-
Pacific Palisades, California
N A-57 Small Town Residential, Cul-de-Sac —
Fillmore, California
O A-61 Small Town Residential, Main Street —
Fillmore, California
P A-65 Suburban Residential in Hill Canyon —
Los.Angeles, California
Q A-69 Farm in Valley — Camarillo, California
R A-73 Grand Canyon, North Rim —Arizona
A-3
-------
Community Description; Large apart-
ment unit, adjacent to San Diego
Freeway in a mixed single multiple
unit residential neighborhood. Eight-
lane major freeway; 0.5 mile to
Venice Boulevard; 1.1 miles to Santa
Monica Freeway; 1.1 mile to a gen-
eral aviation airport.
Noise Environment: This location was
right next to a major freeway. Free-
way traffic produced very high noise
levels most of the day and traffic was
heavy enough to keep the residual noise levels in the high 70 dB(A) range with a
relatively narrow excursion to traffic maximums in the 90 dB(A) range. During the
very early morning hours, with light traffic, the noise level went down into the
40 dB(A) range for several brief periods. No other intruding events are readily
distinguishable on the 24-hour noise signature. The microphone was positioned 100
feet from the side of the freeway and 45 feet above ground level. It projected 6
feet toward the freeway from a third-floor apartment balcony. The freeway street
level was about 30 feet below ground level at the apartment building.
Figure A-la.
Location A — Third Floor Apartment, Next to Freeway —
West Los Angeles, California
A-5
-------
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in 2
Q) £
-a 8
£ O
* I
LI_ O
8
ill
PI
8
O
•O
O O
•— -O
9S!°N
A-6
-------
/OQ JO ttttl
S
o
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i
<
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—
-------
a) Various Measures of the Outdoor Noise Level
110
100
Z 90
3.
O
CN
ID
CO
80
S 70
60
50
40
i T
Hourly Values
Arithmetic
Average of the
Hourly Values
During Period
O
O
O Residual Noise Level
• Maximum Noise Level
(Read from graphic level recordings)
J I
AM
I
J I
PM
i
J I
12 2 4 6 8 10 12 2
Beginning of Hour
8 10 12
Day Eve Night
100
E 80
2 60
O)
f 40
20
b) Histograms of the Percentage of Time Noise Was in Each 5 dB Interval for Three Time Periods
Day Evening Night
40 50 60 70 80 90 40 50 60 70 80 90 40 50 60 70 80 90
A-Weighted Noise Level in dB re 20fiN/m2
Figure A-lc. Summary of the 24-Hour Outdoor Noise Levels
at Location A — Third Floor Apartment, Next to Freeway
A-8
-------
Community Description: Major down-
town metropolitan area, undergoing
considerable reconstruction. The two
major projects were a five-story steel
beam construction above ground on a
commercial building and subterranean
foundation work on a parking garage.
The two projects were located side by
side directly across the street from the
location. Broadway is a four-lane
major downtown street, 0.3 mile to
the Hollywood Freeway and 0.6 mile
to the Harbor Freeway, 1.7 miles to
the Golden State-Santa Ana and Santa Monica Freeways. The general area is a
network of major downtown arteries serving high rise commercial and governmental
buildings, 0.6 mile to railroad station and associated warehousing and industrial
district.
Noise Environment: The noticeable intruding noises, primarily from construction
trucks, cranes and airwrenches, were superimposed on a very high level of steady
traffic noise. Buses and motorcycles were very noticeable within the traffic noise.
Sirens produced the highest levels of intruding noises. The microphone was located
30 feet above the sidewalk, 6 feet away from the side of a relatively open parking
garage structure. A large air conditioning vent at street level, adjacent to the
parking structure, dominated the residual level during the late evening and early
morning hours.
Figure A-2a.
Location B — Third Floor Downtown Hi-Rise —
Los Angeles, California
A-9
-------
Xog
I -
o
P I
I
CNI
< ;
5
IL O
§ 9 S 5 § 5 S
jajgpui |SA9T esio)
I o
A-10
-------
i'i
-Jo
A-11
-------
a) Various Measures of the Outdoor Noise Level
TOO
90
Arithmetic
Average of the
Hourly Values
During Period -
CN
E
•Z 80
O
CM
a>
i_
CD
70
.2 60
'o
Z
" 40
c
o
£ 20
r r i i
40 50 60 70
80
i i i r
40 50 60 70 80
\ i r
40 2 50 60 70 80
A-Weighted Noise Level in dB re 20MN/m
Figure A-2c. Summary of the 24-Hour Outdoor Noise Levels
at Location B —Third Floor Downtown Hi-Rise
A-12
-------
Community Description: Harlem sec-
tion of New York City; metropolitan
low income residential and commer-
cial area; at the intersection of 125th
Street and Lenox which are both major
four-lane arterials; one mile to the
East River; 25 miles to a major metro-
politan commercial airport.
Noise Environment: Major intruding
noises were generated by trucks,
motorcycles, sirens, fire engines, and
jet overflights superimposed on fairly
steady levels of automobile traffic, loud music and voice announcements being
played as part of a store front promotion continually from 10:00 a.m. to midnight.
Considerable amounts of "people noise" were noted during times when rain was not
falling. The microphone was located just inside an open window on the second floor
of a business building. This location was approximately 55 feet from the actual
corner of the building. The window faced Lenox Street.
Figure A-3a.
Location C —Second Floor Tenement —
Harlem, New York
A-13
-------
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A-U
-------
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8
A-15
-------
a) Various Measures of the Outdoor Noise Level
no
100 -
CM
Z 90
3.
o
CN
80
1)
a>
-,n
70
o
Z
60
50
40
i i I I i i i
Hourly Values
I I
Arithmetic
Average of the
Hourly Values
During Period
O Residua! Noise Level
* Maximum Noise Level
(Read from graphic level recordings)
A.M.
P.M.
j I
I I I 1 I I
I 1
12 2
6 8 10 12 2
Beginning of Hour
4 6 8 10 12 Day Eve Night
100
80
•o 60
O)
| 40
-------
Community Description: Major com-
mercial shopping center; large and
small stores, major department stores,
high rise office buildings and service
stations; 200 feet to Hawthorne Boule-
vard, a six-lane arterial; 150 feet to
Carson, a four-lane arterial; 1.Smiles
to Pacific Coast Highway, a major
four-lane arterial; 2.75 miles to the
San Diego Freeway, 3.75 miles to the
Harbor Freeway, 1.5 miles to a major
small general aviation airport, 1.5
miles to nearest industrial area, and
2.25 miles to a beach.
Noise Environment; Heavy street traffic dominated almost the entire 24-hour period.
A store air conditioner vent held up the residual level during the early morning
hours. Intruding noises superimposed on the general traffic noises were jet and
propeller overflights, trucks, motorcycles, horns, trucks and service equipment for
nearby lots and stores. The microphone was located 25 feet above ground, 200 feet
from Hawthorne Boulevard, and 150 feet from Carson Boulevard.
Figure A-4a.
Location D — Urban Shopping Center —
Torrance, California
A-17
-------
KOQ jo
8
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£ J
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£ 2
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8 3 8
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8
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8 §8 38
1
1^
38 3
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A-18
-------
JO 9UII|
-------
a) Various Measures of the Outdoor Noise Level
100
90
Z 80
3.
O
CM
£
CD
70
X 60
'6
40
I I I
Hourly Values
I
Arithmetic
Average of the
Hourly Values
During Period _
O Residual Noise Level
• Maximum Noise Level
(Read from graphic level recordings)
AM
I
i i I I
PM
i
12 2 46 8 10 12 2 4 6
Beginning of Hour
8 10 12
Day Eve Night
b) Histograms of the Percentage of Time Noise Was in Each 5 dB Interval for Three Time Periods
Day Evening Night
IUU
u 80
€
'S 60
-------
BE
Light
Community Description: Major recrea-
tion beach state park; large parking
area but no major high speed arterials
or streets nearby. 0.5 mile to Pacific
Coast Highway; channel entrance to a
very large recreational boating and
bay area. The beach and parking
area is about 0.2 mile wide and
located at base of a 75-foot bluff.
Noise Environment: Major intruding
events were due to a variety of air """"""
vehicles; several helicopters and small
propeller aircraft at close range, and commercial jets at greater distances. Con-
siderable noise during the day came from recreational activity on the beach and in
the refreshment stand area. The residual noise during the evening was dominated by
the surf which varied from 50 to 60 dB(A) with the breaking of the waves. During
the day the recreational activity raised the residual level to the 56 to 58 dB(A)
range and no surf noise pattern is noticeable on the record. An unusual intruding
event was the beach sand cleaner at 7:30 a.m. The microphone was located about
100 yards from the surf at the junction of the sand and parking lot. It was placed
20 feet above ground level and above a partially covered breezeway about 75 feet
from the refreshment stand.
Figure A-5a.
Location E — Popular Beach on Pacific Ocean —
Corona Del Mar, California
A-21
-------
X
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iO
I
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A-?2
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02
A-23
-------
100
90
80
£
CO
70
8 60
'5
T>
0)
it" 50
I
40
30
Hourly Values
O Residual Noise Level
• Maximum Noise Level
(Read from graphic level recordings)
I I
12
AM
I
I J I I
PM
8 10 12 2 4
Beginning of Hour
Arithmetic
Average of the
Hourly Values
During Period .
8 10 12
Day Eve Night
100
80
0 60
ai
D)
f 40
H
I 20
Day
Evening
Night
n
r • i' ' i""—-i—i—r * r * i 1—i—r
30 40 50 60 70 30 40 50 60 70 30 40 50 60 70
A-Weighted Noise Level in dB re 20/iN/m2
Figure A-5c. Summary of the 24-Hour Outdoor Noise Levels
at Location E — Popular Beach on Pacific Ocean
A-24
-------
Community Description: Suburban
residential; single family dwellings
only; 36-foot-wide street wfth only
neighborhood traffic; 0.25 mile to
Hawthorne Boulevard, a six-lane
arterial; 0.3 mile to Century Boule-
vard, a six-lane major arterial; 0.7
mile to Imperial Highway, a four-
lane arterial; 0.7 mile to the San
Diego Freeway, 4.4 miles to the
Harbor Freeway; located in the
approach pattern, 0.75 mile to a
major metropolitan airport.
Noise Environment: Intruding noise events were generated primarily by the jet air-
craft approach traffic. The maximum noise levels were generally in the range of
100 dB(A). Events occurred at typical rates of 30 per hour during daytime and 6 per
hour during the morning hours. Automobiles and dogs created the other intruding
events with traffic setting the residual noise levels. The microphone was located
55 feet from the curb and 24 feet above ground.
Figure A-6a.
Location F — Urban Residential, Near Major Airport —
Lennox, California
A-25
-------
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n 2
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O
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A-26
-------
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T
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_
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02
as!°N
A-27
-------
a) Various Measures of the Outdoor Noise Level
Arithmetic
Average of the
Hourly Values
During Period
2 46 8 10 12 246
Beginning of Hour
8 10 12
Day Eve Night
TOO
80
° 60
a
c 40
o
u
<£ 20
b) Histograms of the Percentage of Time Noise was in Each 5 dB Interval for Three Time Periods
Day Evening Night
1 I T ' | I I I II T
45 55 65 75 85 95 45 55 65 75 85 95 40 50 60 70 80
2
A-Weighted Noise Level in dB re 20 pN/m
Figure A-6c. Summary or me 24-Hour Outdoor Noise Levels
at Location F— Urban Residential, Near Major Airport
A-28
-------
Community Description: Suburban res-
idential; single family dwellings only;
22 foot wide street, 2 blocks long;
only traffic local to the dwellings on
the street; 0.3 mile to Palos Verdes,
a four-lane arterial; 0.5 mile to
Pacific Coast Highway, a major four-
lane arterial; 4.5 miles to San Diego
Freeway, 5.5 miles to the Harbor
Freeway, 2 miles to major general
aviation airport, 2 miles to major
shopping and financial district; 4
miles to nearest industrial area; and
0.6 miles to beach.
Noise Environment: The major intruding noises were from single engine aircraft from
the nearby general aviation airport and from jet overflights from a major metropolitan
airport. Background traffic from adjoining streets and arterials, sirens, children on
the street, delivery and service trucks formed the other intruding sources. Residual
noise levels were dominated by urban traffic. A water company diesel generator
across the street increased the residual level by 5 dB(A) for 3 hours during the early
evening. A street sweeper, motorcycle, helicopter, and a neighbor hooking up a
trailer were the unusual single events for the 24-hour period. The microphone was
located 40 feet from the curb and 20 feet above street level. The 24-hour noise
level charts for this location were produced on a different chart paper than that used
at the other 17 sites.
Figure A-7a.
Location G — Urban Residential, Near Ocean —
Redondo Beach, California
A-29
-------
Figure A-7b. Time History
LOCATION G - 0000 Hours to 1200 Hours
0500
8
£
I
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: "...": 0600
0700
~r 0800
'
""fig '"'—"ft
IZZH~ 1200
^'U VAAv4-W:^%Q-
A-30
-------
LOCATION G - 1200 Hours to 2400 Hours
---/*+-
wb^
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1-
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90 -
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Liiitik>~,TV T^rjiui^Taita^AJ/^T^L/tj. jtomuUumjr v^o
40 '
90 '
._ ........ ______
t
30
Minutes
50 60
A-31
-------
100
90
Z 80
a
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CN
5
a>
I 40
0)
o
<5 on
a- 20
b) Histograms of the Percentage of Time Noise was in Each 5 dB Interval for Three Time Periods
Day Evening Night
30 40 50 60 70
30 40 50 60 70 30 40 50 60 70
A-Weighted Noise Level in dB re 20^N/m
Figure A-7c. Summary of the 24-Hour Outdoor Noise Levels
at Location G - Urban Residential, Near Ocean
A-32
-------
u
Community Description: High density
single family dwellings in an urban
residential area, 34 feet wide street
with light residential traffic, 0.3 mile
to Alameda; 0.75 mile to Imperial
Highway and 1.2 miles to Central
Avenue, all four-lane arterials; 2.7
miles to the Harbor Freeway, 0.3 mile
to a heavy industrial area and multiple
track railroad and siding yard; under
the approach pattern and 8 miles to a
major metropolitan commercial airport.
Noise Environment: The major intruding single events were produced by jet aircraft
during landing approach, automobiles, dogs, helicopters, and children playing.
Other intruding events were from the railroad, a factory whistle, and two large
scrap iron yards in the area. Residual sources were difficult to assess but probably
were governed by a combination of urban traffic and industrial noise during the
entire day. Aircraft overflights were of long duration and at moderately high noise
levels, with no interval between event thresholds during the busier periods. The
microphone was located 50 feet from the street and 20 feet above ground level.
Figure A-8a.
Location H — Urban Residential, 6 miles to Major Airport —
Los Angeles, California
A-33
-------
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A-34
-------
JO
8 1
A-35
-------
a) Various Measures of the Outdoor Noise Level
O Residual Noise Level
• Maximum Noise Level
(Read from graphic level recordings)
Hourly Values
Arithmetic
Average of the
Hourly Values
During Period
12 2 4 6 8 10 12 2 4 6 8 10 12 Day Eve Night
Beginning of Hour
b) Histograms of the Percentage of Time Noise Was in Each 5 dB Interval for Three Time Periods
Day Evening Night
01
D)
D
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-------
Community Description: Suburban resi-
dential at the outskirts of a large
metropolitan area; 36-foot wide street
serving only neighborhood traffic; 350
feet to Los Angeles Avenue, a four-
lane major arterial; 0.7 mile to the
Si mi Freeway; 300 feet to the Southern
Pacific Railroad track, 0.6 mile to
light commercial and business district,
1.0 mile to a small aircraft landing
strip.
Noise Environment: Major intruding
noise events were produced by trains, small airplane overflights, and automobiles.
Other intruding noises were produced by dogs and an ice cream vendor, motorcycles,
children playing, and a rocket test burst from the Santa Susana rocket test stand
area. Minimum noise levels during the midnight hour were set by a train idling on a
siding. The microphone was located 50 feet from the curb and 18 feet above ground.
Figure A-9a.
Location I - Suburban Residential, Near R/R Tracks —
Simi Valley, California
A-37
-------
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A-38
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XDQ to euju
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a) Various Measures of the Outdoor Noise Level
^
Z
o
CN
0)
CO
0)
0)
O
Z
90
80
70
60
50
Arfthmetic
Average of the
Hourly Values
During Period
•? 40
30
20
O Residual Noise Level
• Maximum Noise Level
(Read from graphic level recordings)
A.M.
I
P.M.
12
6 8 10 12 2
Beginning of Hour
8 10 12
Day Eve Night
100
« 80
'o 60
CD
D)
| 4°
O
£ 20
b) Histograms of the Percentage of Time Noise was in Each 5 dB Interval for Three Time Periods
Day Even_mg_ Night
i T
30 40 50 60 70
rfTTfT.
I I I \ I
30 40 50 60 7"
2
A-Weighted Noise Level in dB re 20 u.N/m
30 40 50 60 70
Figure A-9c. Summary of the 24-Hour Outdoor Noise Levels
at Location I - Suburban Residential, Near R/R Tracks
A-40
-------
Community Description: Suburban resi-
dential; single family dwellings only
with some apartments and a hospital in
nearby area; 36-foot wide street, a
three-block closed circle; only traffic
local to dwellings on the street; 0.2
mile to Prairie, a four-lane street,
0.25 mile to Manchester Avenue and
Florence Avenue, four-lane arterials;
0.3 mile to Hawthorne-LaBrea, a
major four-lane arterial; 1.3 miles to
San Diego Freeway; 3.8 miles to Har-
bor Freeway; 2 miles to major metro-
politan airport; 0.25 mile to large cemetery and park area; 0.5 mile to major recre-
ational and park area.
Noise Environment: The major intruding noises were from jet aircraft landings. The
takeoff runup and climbout rumble formed a very unusual noise pattern. The sideline
distance to the major air traffic kept the levels down, but formed some very long
duration intruding events. The residual noise levels were generated primarily by the
heavy arterial traffic in the area. Service trucks, lawn mowers, and cars produced
the other intruding events. A garbage truck and a rock band practice were the
sources of some unusual single events. The microphone location was 40 feet from
curb and 20 feet above ground.
Figure A-lOa. Location J — Urban Residential —
Inglewood, California
A-41
-------
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A-42
-------
XDQ jo
9P u!
A-43
-------
a) Various Measures of the Outdoor Noise Level
O Residual Noise Level
• Maximum Noise Level
(Read from graphic level recordings
Arithmetic
Average of the
Hourly Values
During Period
Hourly Values
12 2
8 10 12 2
Beginning of Hour
Day Eve Night
100
I 80
0 60
o
40
20
b) Histograms of the Percentage of Time Noise Was in Each 5 dB Interval for Three Time Periods
Day Evening Night
30 40 50 60 70 30 40 50 60 70 30 40 50 60 70
A-Weighted Noise Level in dB re 20fiN/m
Figure A-lOc. Summary of the 24-Hour Outdoor Noise Levels
at Location J — Urban Residential
A-44
-------
=ff'<1 ,
.// /.('moiia (If1 Mar |
,A Hijfh H
Community Description: Suburban resi-
dential; large single family dwellings
only; 36-foot wide street serving only
local traffic for a 2-block length; 0.4
mile to Dover Drive, a four-lane
arterial; 1.4 miles to Newport Boule-
vard, 1.3 miles to Pacific Coast High-
way, 1.8 miles to McArthur Boulevard,
all major four-lane arterials; 3.5 miles
to a major general aviation airport
which has approximately 30 commer-
cial jet flights daily; 0.3 mile from
climbout ground track; 3.5 miles from
takeoff brake release; 3.6 miles to the San Diego Freeway.
Noise Environment: Major intruding noise sources were created by commercial jet
aircraft in their climbout pattern, a few helicopter events, propeller airplanes and
some automobile noise. Other intruding events results from dogs barking, lawn
mowers, hammering, a car revving up across the street, a garbage can rolling down
a driveway, and jet engine thrust reversals at the airport. The residual noise levels
were relatively low and seemed uninfluenced by the presence of crickets at this
location. Cricket activity is noticeable on the 24-hour record during the 0100 hour
when one or more crickets were relatively close to the microphone. The residual
noise levels were apparently dominated by neighborhood activity and distant traffic.
The microphone was located 45 feet from the curb and 20 feet above ground level.
Figure A-l la.
Location K— Urban Residential, Near Small Airport —
Newport Beach, California
A-45
-------
^ i
O J
£
i
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D
D) 3
tn Q
88 88 88 §8 §8 §8 §8
A-46
-------
XDQ jo
8
a
£
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•o
3
A-47
-------
a) Various Measures of the Outdoor Noise Level
90
80
Z 70
o
CN
a
60
.§ 50
o
Z
•-
I 40
30
20
I I I I I I I I I T I I
Hourly Values 9 9
Arithmetic
Average of the
Hourly Values
During Period
O Residual Noise Level
• Maximum Noise Level
(Read from graphic level recordings)
AM
PM
I i 1 I
J 1
100
80
0 60
-------
Community Description: Urban resi-
dential; mostly single family dwellings
with light commercial district along
nearby arterials; 36-foot wide street
serving only residential traffic; 0.2
mile to Vermont Avenue, a four-lane
major arterial; 0.2 mile to Adams
Boulevard, a four-lane arterial; 0.5
mile to the Santa Monica Freeway;
1.1 miles to the Harbor Freeway; 2
miles to the major metropolitan down-
town area.
Noise Environment: The major intruding events were produced by airplanes, heli-
copters, automobiles and dogs. Other measurable events were created by a lawn
mower, an ice cream vendor, a radio playing on a porch front, and children playing.
From 6:00 a.m. to 7:00 a.m., the residual noise level rose 10 dB(A) due to noise
from the Santa Monica Freeway. The microphone location was 50 feet from the curb
and 25 feet above ground level. The microphone was on a line of site exposure to the
freeway. The residual noise level was 2 to 4 dB(A) lower at ground level during the
6:00 a.m. to 7:00 a.m. rise in residual level due to freeway activity.
Figure A-12a.
Location L — Old Residential, Near City Center —
Los Angeles, California
A-49
-------
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A-51
-------
a) Various Measures of the Outdoor Noise Level
Z
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CD
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c
90 -
80 -
70 -
60
$
(U
SJ 50
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30
20
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Hourly Values
j I
12
O Residual Noise Level
• Maximum Noise Level
(Read from graphic level recordings)
A.M.
P.M.
I I i i
Arithmetic
Average of the
Hourly Values
During Period
6 8 10 12 2
Beginning of Hour
6 8 10 12
Day Eve Night
100
b) Histograms of the Percentage of Time Noise was in Each 5 dB Interval for Three Time Periods
Day Evening Night
80 -
60
-------
Community Description: Suburban resi-
dential; large moderately spaced
single family dwellings only; 28-foot
wide street serving a six square block
residential area; 0.1 mile to Sunset
Boulevard, a major four-lane arterial
with mostly residential and little
commercial traffic; 0.6 mile to San
Vicente Voulevard, a four-lane resi-
dential arterial; 2.3 miles to the San
Diego Freeway; 3.8 miles to a gen-
eral aviation airport.
Noise Environment: The major intruding noises were from jet overflights at approxi-
mately 4000-6000 feet altitude, and from automobiles on the residential street. The
other intruding sources were dogs in the residential area and street traffic intruding
from nearby Sunset Boulevard. The residual noise level appeared to be dominated
by traffic noise in the general area. The microphone was 25 feet from the curb and
4 feet above ground level so residential street traffic at this location is exaggerated
compared to the other intruding events at this location, and to street traffic at other
residential locations due to the microphone's closer proximity to the street and
ground level.
Figure A-13a.
Location M — Suburban Residential at City Outskirts —
Pacific Palisades, California
A-53
-------
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A-54
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A-55
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a) Various Measures of the Outdoor Noise Level
90
80
Z 70
o
CN
60
o
Z
I
I 40
30
20
Hourly Values
• Maximum Noise Level
(Read from graphic level recordings)
A.M.-
i i
P.M.
I i
12 2 4 6 8 10 12 2
Beginning of Hour
8 10 12
Arithmetic
Average of the
Hourly Values
During Period
Day Eve Night
100
b) Histograms of the Percentage of Time Noise was in Each 5 dB Interval for Three Time Periods
Day (7 a.m. - 7 p.m.) Evening (7 p.m. - 10 p.m.) Night (10 p.m. - 7 a. m.)
I 1 i
30 40 50 60 7
A-Weighted Noise Level in dB re 20
30 40 50 60 70
2
Figure A-13c. Summary of the 24-Hour Outdoor Noise Levels
at Location M —Suburban Residential at City Outskirts
A-56
-------
ml.
a*.
Community Description: Small town
(population 6200); cul-de-sac with
no through traffic; 2 to 4 blocks to the
main north-south and east-west streets;
0.6 mile to State Highways 126 and
23 (two-lane surfaced highways); 0.4
mile to the main business district; 0.5
mile to the Southern Pacific Railroad
track.
Noise Environment: The major intrud-
ing noises were from propeller aircraft
and helicopter overflights, background
traffic on nearby streets, cars in the cul-de-sac, dogs barking, people talking, and
children playing in the area. A street sweeper in the cul-de-sac provided the
highest noise level during the day. The residual noise level in the evening has some
cricket activity present, but they do not seem to have controlled the noise. The
residua! noise level was apparently governed by community activity and traffic, and
appears to have random fluctuations during any given hour. In large urban areas,
the residual noise level appears either constant or qradually changing over any hour
period. The microphone was located 20 feet from ,ne curb and 4 feet above the
ground.
Figure A-14a.
Location N -Small Town Residential, Cu I-de-Sac —
Fillmore, California
A-57
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a) Various Measures of the Outdoor Noise Level
90
80
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CM
£
ta
•° 60
ID
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8 50
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Z
40
30
20
Hourly Values
Arithmetic
Average of the
Hourly Values
During Period
12
Residual Noise Level
* Maximum Noise Level
(Read from graphic level recordings)
— A.M. —
I i i
P.M. -
i i
6 8 10 12 2
Beginning of Hour
8 10 12
Day Eve Night
b) Histograms of the Percentage of Time Noise was in Each 5 dB Interval for Three Time Periods
Day Evening Night
IUU
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0>
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n
-
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30 40 50 60 70
30 40 50 60 70 30 40 50 60 70
2
A-Weighted Noise Level in dB re 20 uN/m
Figure A-14c. Summary of the 24-Hour Outdoor Noise Levels
at Location N —Small Town Residential, Cul-de-Sac
A-60
-------
Community Description: Small town
(population 6200); main street resi-
dential area; 0.3 mile to State High-
way 23 and 0.6 mile to State Highway
126, both two-lane surfaced highways;
0.2 mile to the main business district;
0.5 mile to the Southern Pacific Rail-
road track.
Noise Environment: The major intrud-
ing noise sources were from main street
traffic, airplanes, trucks and motor-
cycles, horns and lawn mowers.
During the midnight to 0100 time period, there were as many aircraft overflights as
cars passing on the main street. The residual noise level in the late evening hours
appeared more steady than at the cul-de-sac location 5 blocks away (location N).
The microphone was located 55 feet from the curb and 5 feet above ground.
Figure A-l5a.
Location O—Small Town Residential, Main Street —
Fillmore, California
A-61
-------
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A-63
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a) Various Measures of the Outdoor Noise Level
80
70
60
50
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o
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a
I 30
^
20
10
T
T
T
1 r
Hourly Values
O Residual Noise Level
• Maximum Noise Level
(Read from graphic level recordings)
A.M.
P.M.
j i_
Arithmetic
Average of the
Hourly Values
During Period
12 2 4 6 8 10 12 2
Beginning of Hour
8 10 12
Day Eve Night
100
1 80
b) Histograms of the Percentage of Time Noise was in Each 5 dB Interval for Three Time Periods
Day Evening Night
60
40
20
0
i r
30 40 50 60 70
30 40 50 60 70
30 40 50 60 70
A-Weighted Noise Level in dB re 20 uN/m
Figure A-15c. Summary of the 24-Hour Outdoor Noise Levels
at Location O— Small Town Residential, Main Street
A-64
-------
Community Description: High income
surburban residential canyon area, 30-
foot wide two-lane street, 2.5 miles
long, forming an arterial for all the
traffic to and from the dwellings along
the canyon road, 0.75 mile to the San
Diego Freeway, 2 miles to a major
suburban and commercial business
district. Street and houses located
along the bottom of a narrow canyon
about 300 feet deep.
Noise Environment: Heavy street
traffic formed the dominant intruding noise. A few aircraft overflights, dogs and
children playing formed the other noticeable single events. The residual level is
relatively low, except when dominated by crickets during evening and night hours.
The crickets raised the residual noise 12 dB(A) in a 20-minute period beginning
about 2000 hours. The residual noise level dropped about 15 dB(A) between 4:00
a.m. and 6:00 a.m. when the crickets quieted down. The microphone was located
40 feet from the curb and 25 feet above ground level.
Figure A-16a.
Location P —Suburban Residential in Hill Canyon —
Los Angeles, California
A-65
-------
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I
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A-67
-------
a) Various Measures of the Outdoor Noise Level
90
Arithmetic
Average of the
Hourly Values
During Period
20
100
080
Day Eve Night
b) Histograms of the Percentage of Time Noise Was in Each 5 dB Interval for Three Time Periods
Day Evening Night
60
40
£ 20
nfTTl
30 40 50 60 70 30 40 50 60 70
A-Weighted Noise Level in dB re
20 30 40 50 60
m
Figure A-16c. Summary of the 24-Hour Outdoor Noise Levels
at Location P— Suburban Residential in Hill Canyon
A-68
-------
Community Description: Rural agri-
cultural area tomato field; 50 yards to
the trees around the yard and dwelling
area; 160 yards to Walnut Avenue, a
lightly traveled surface road; 0.6 mile
to State Highway 118, a two-lane
moderately traveled highway; 0.6 mile
to LaLoma Avenue and 0.75 mile to La
Vista Avenue, both lightly traveled
surfaced roads; 3.5 miles to the Santa
Paula Freeway; 3.6 miles to the
Ventura Freeway; 4.5 miles to Camarillo.
Noise Environment: The major intruding events were created by jet and propeller air-
craft flyovers and dogs barking. Other intruding events were from background traffic
noise. Trucks on the distant freeways could be heard distinctly but did not raise the
noise level above its residual value. The residual noise level during the evening
hours was dominated by crickets. During the day an orchard pruner in the distance
controlled the minimum noise level. The microphone was located 5 feet above ground
level.
Figure A-17a. Location Q — Farm in Valley —
Camarillo, California
A-69
-------
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CO 00 CO QO CO
gp ui
A-71
-------
a) Various Measures of the Outdoor Noise Level
O Residual Noise Level
• Maximum Noise Level
(Read from graphic level recordings)
Arithmetic
Average of the
Hourly Values
During Period
Hourly Values
12 2 46 8 10 12 2 4
Beginning of Hour
8 10 12
Day Eve Night
100
« 80
o 60
I
1 40
(0
o
«£ 20
b) Histograms of the Percentage of Time Noise was in Each 5 dB Interval for Three Time Periods
Day Evening Night
20 30 40 50 60
20 30 40 50 60 20 30 40 50 60
A-Weighted Noise Level in dB re 20 pN/m
Figure A-17c. Summary of the 24-Hour Outdoor Noise Levels
at Location Q— Farm in Valley
A-72
-------
Community Description: Remote wilder-
ness; north rim of the Grand Canyon;
a campground with four picnic tables
accessible by a 100-mile dirt road
from St. George, Utah.
Noise Environment: Extremely quiet.
Major intruding noises were generated
by propeller overflights and small
animals and insects. Crow calls from
a quarter of a mile away were clearly
audible, and feather aerodynamic
noise from birds no larger than sparrows
was noticeable from 30 to 40 feet away. The sounds of the rapids in the Colorado
River, 3000 feet below, were clearly audible when the observer stood at the edge of
the canyon, considerably attenuated 5 to 10 feet from the edge, and completely
inaudible 40 feet from the edge. The canyon seems to act as a highly directional
horn radiating this sound vertically.
In this location, nighttime noise greatly exceeded daytime noise because of crickets.
Daytime animal noises consisted of barking by chipmunks and bird noises mentioned
above. The microphone was located in a sheltered area a few feet downwind from
some rocks approximately 150 feet from the edge of the canyon. At this location,
the noise level frequently fell below the 16 dB(A) threshold of the measurement
instrumentation. In order to make a measurement of the correct level, the sensi-
tivity of an auxiliary sound level meter was set to a maximum level, extending
the measurement range to about 11 dB(A).
Figure A-18a. Location R- Grand Canyon, North RTm-
Arizona
A-73
-------
8
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A-74
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A-75
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a) Various Measures of the Outdoor Noise Level
70
60
Z 50
3.
O
CN
40
.§ 30
o
T>
a>
•4-
% 20
I
10
Hourly Values
Arithmetic
Average of the
Hourly Values
During Period
O Residual Noise Level
• Maximum Noise Level
(Read from graphic level recordings)
AM
I
PM
I
12
6 8 10 12 2
Beginning of Hour
8 10 12
Day Eve Night
b) Histograms of the Percentage of Time Noise Was in Each 5 dB Interval for Three Time Periods
Day Evening Night
i 80
S 60
O5
1 40
o
20
10 20 30 40
1
50
10 20 30
A-Weighted Noise Level in dB re 20 fiN/m
10 20 30 40 50
40 50
Figure A-18c. Summary of the 24-Hour Outdoor Noise Levels
at Location R — Grand Canyon, North Rim
A-76
-------
A. 2 Data Acquisition and Reduction
A.2.1 Introduction
Data acquisition and reduction for the community noise survey was performed
with the three systems depicted in Figure A-19 — Standard Field Measurement System,
Figure A-20 — Low Noise Field Measurement System, and Figure A-21 — Data Reduction
System. Details of the application of each system, system configuration, operating
procedures and performance specifications are presented in the following paragraphs.
A.2.2 Data Acquisition Systems
A. 2.2.1 Standard Field Measurement System
The Standard Field Measurement System was used on locations where the
ambient level of the community noise data was higher than 30 dB(A) — 13 of the 18 survey
locations. It was a fully self-contained field laboratory, used for making continuous
graphic level and magnetic tape recordings of the community noise levels. All equipment
in this van operated from 115 vac; therefore, the system was used only at measurement
locations with accessible line power.
A.2.2.1.1 System Description
Noise data was acquired through a condenser microphone shielded by a wind-
screen. Microphone signals were conditioned by a preamplifier and input to a microphone
amplifier for amplification and A-weighted filtering. The microphone amplifier, in turn,
drove a graphic level recorder and a magnetic tape recorder. A statistical distribution
analyzer was mechanically coupled to the pen driving mechanism of the graphic level
recorder. Data was continuously recorded on one track of the tape recorder; appropriate
operator commentary was recorded on the other track.
A.2.2. 1.2 Operating Procedures
To perform a 24-hour noise survey, the equipment was first interconnected as
illustrated in Figure A-19, with the exception that the output of the audio oscillator was
fed to the input of the tape recorder. A series of sinusoidal signals ranging from 90 Hz to
12 KHz was then input to the tape recorder, and a frequency response calibration recorded
on tape. Next, the oscillator was utilized to calibrate the statistical distribution analyzer
and the graphic level recorder over the 50 dB chart range.
A-77
-------
Following recorder calibration, the preamplifier was connected to the micro-
phone amplifier. A B & K Type 4230 acoustic calibrator was placed on the microphone,
and the sensitivities of the graphic level recorder and tape recorder were adjusted to this
reference level of 93.6 dB (re 20 pN/m^). This operation completed the pre-run
calibration procedure.
Following calibration, the graphic level recorder, the tape recorder, and the
statistical distribution analyzer were activated and the 24-hour measurement commenced.
At the completion of each hour, the statistical distribution analyzer was stopped; the
amplitude distribution readings were recorded, and the analyzer was "zeroed" and restarted.
During this same period — about 10 minutes — the tape was removed from the tape recorder
and a new reel of tape installed. A reference voltage, with a fixed relationship to the
microphone calibration, was put on the beginning of each reel of tape.
When the community noise data rose above, or fell below, the 50 dB range of
the graphic level recorder, the microphone amplifier attenuator was adjusted to accommodate
the dynamic range of this data. At periodic intervals over the measurement period, the
system was also calibrated with the acoustic calibrator.
A.2.2.1.3 Specification
System Measurement Range: 28 dB(A) to 130 dB(A)
System Frequency Response: 20 Hz to 10 KHz
Statistical Distribution Analyzer: Measured elapsed time of data in 10 bands,
each of 5 dB bandwidth. Elapsed time
above the top band and below the bottom
band was also recorded.
A.2.2.2 Low Noise Field Measurement System
This system was used for making measurements at locations where (1) 115 vac
power was not available, or (2) the community noise threshold dropped below the lower
limits of the Standard Field Measurement System. This system was used at five of the
survey locations. The system provided magnetic tape records, but no graphic records, of
the 24-hour noise history. Tapes were subsequently played back in the laboratory on the
data reduction system to obtain the amplitude time histories and the statistical data.
A-78
-------
A.2.2.2.1 System Description
Community noise data were acquired through a condenser microphone shielded
by a windscreen. This microphone was attached to a preamplifier connected to a
precision sound level meter. The sound level meter, in turn, drove a magnetic tape
recorder through 100 feet or less of cable.
A.2.2.2.2 Operating Procedure
To perform a 24-hour noise survey, the equipment was interconnected as
shown in Figure A-22. System frequency and dynamic response checks were performed
in the laboratory prior to field measurements, as the nature of the survey sites did not
permit taking any non-portable or bulky equipment into the field.
Pre-test calibration of the sound level meter and the tape recorder were
performed with the acoustic calibrator at 93.6 dB. Following calibration, the sound level
meter and the tape recorder were activated and the 24-hour measurement commenced. A
microphone calibration was put on the beginning and end of each reel of tape. One
tape ran for three hours; consequently, eight tape changes were required during a
survey. Tape records were monitored by headphone during the noise survey.
A.2.2.2.3 System Specification
Overall Measurement Range: 16 dB(A)* to 130 dB(A)
Overall Frequency Response: 20 Hz to 10 KHz
*The 16 dB(A) floor was set by the recording system —an auxiliary
sound level meter had a noise floor of 11 dB(A).
A.2.3 Data Reduction System
The data reduction system — shown in Figure A-23 — was used to obtain
(1) time history and statistical analysis records of the data from the Low Noise Field
Measurement System, and (2) one-third octave band analyses of data from all 18 noise
survey locations.
A.2.3.1 System Description
A.2.3.1.1 Time History Records
Tape recordings from the Low Noise Field Measurement System were replayed
— with the same tape recorder used in the field — into a graphic level recorder and statistical
A-79
-------
distribution analyzer. This data reduction was essentially identical to the method used
for making the 24-hour noise survey with the Standard Field Measurement System. The
graphic level recorder was calibrated by using the reference signal recorded on tape.
The microphone amplifier was set to provide an A-weighted output signal, and the 24-hour
records were all replayed into the graphic level recorder.
A.2.3.1.2 One-Third Octave Band Plots
The first step in obtaining this data was to select the specific events on the
24-hour record to be analyzed. Once this data was located on the original graphic record,
a second graphic record of the data was recreated from the magnetic tape to verify that the
proper data was located on tape. The portion of the taped record to be analyzed was then
played into the real-time analyzer and a graphic record of the third octave spectrum
obtained. To obtain one-third octave plots of data, taken with the Standard Field
Measurement System, a correction from A-weighting to linear was applied to output of
the spectrum analyzer.
A.2.3.2 Statistical Analysis
Data from the statistical distribution analyzer consisted of records of (1) the
elapsed time that the A-weighted level of the community noise data was below the bottom
of the graphic level recorder chart, (2) the elapsed time the level of the data was greater
than the top of the graphic record, and (3) the elapsed time the data remained within each
of ten 5 dB wide bands covering the 50 dB range of the graphic level recorder. This data
was subsequently processed on a CDC 6600 computer to obtain the statistical distributions
for each site.
A-80
-------
Windscreen
&
Microphone
B&K 4131/4133
Preamplifier
B&K 2615
Microphone
Amplifier
B&K 2603
Tape
Recorder
Sony 770
Graphic Level
Recorder
B&K 2305
Audio
Oscillator
HP200 CD
Oscilloscope
HP 122AD
Parch
Patch
Statistical
Distribution
Analyzer
B&K 4420
Figure A-19. Standard Field Measurement System
Sound
Level
Meter
B&K 2204
Windscreen
&
Microphone
B&K 4131
Tape
Recorder
Nagra IV
Figure A-20. Low Noise Field Measurement System
A-81
-------
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APPENDIX B
TYPICAL NOISE SPECTRA
This appendix contains typical examples of noise spectra measured at
some of the locations. The data were reduced on a real time analyzer using slow
random averaging for the residual spectra and maximum for the spectra of vehicle
pass-bys or other events denoted by maximum.
Measurements are at various distances from the various sources, and
therefore should not be used to compare the absolute magnitude of the various
sources. However, they give an indication of the relative spectral characteristics
of the different sources.
Figures B-l through B-3 are for aircraft; Figures B-4 through B-9 are
for various ground transportation vehicles; Figure B-10 has some typical beach
sounds; and Figures B-ll through B-l3 have some sounds from nature which include
crickets, birds and dogs.
B-l
-------
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T> 90
80
70
60
50
1 .4 Miles to Touchdown
5 100
High Bypass
Low Bypass
6 Miles to Touchdown —
5 1000 2
Frequency in Hertz
10,000
Figure B-2. Landing of Large Turbofan Aircraft
B-3
-------
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50
40
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Approximately 4000 to
7000 Feet Slant Range
i I i i
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5 100
5 1000 2
Frequency in Hertz
10,000
Figure B-3. Overflight of Large Turbofan Aircraft During Climbout
B-4
-------
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Normal Range
Typical Minimum Residual
Noise Level (5:00 a.m.)
. . I . . ..
I . . I.I
100 2 5 1000 2
Frequency in Hertz
10,000
Figure B-4. Freeway, from 3rd Floor Apartment, Location A
B-5
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\ //\ xS/«.'V "*" ^v S* ^'^ / a^ Noon and ~
\\ fjfo N V ' N Kj 4 : 00 p . m .
\ / \ \ \\
\ ' ^^^''^''"v ^
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Daytime Residual at — ' v \\
Noon and 4:00 p.m. V \ >
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Nighttime Residual —-/ ^.
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100 2 5 1000 2
Frequency in Hertz
10,000
Figure B-5. Downtown City Noise, Los Angeles, Location B
B-6
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Truck on Freeway
Bus — Downtown
Los Angeles
c
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I .
100
5 1000
Frequency in Herrz
10,000
Figure B-6. Example of Maximum Noise Level of
a Truck and a City Bus
B-7
-------
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Frequency in Hertz
10,000
Figure B-7. Example of Maximum Noise Levels for Motorcycles
B-8
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Frequency in Hertz
10,000
Figure B-8. Miscellaneous Automobile Noises
B-9
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10,000
Figure B-9. Freight Train at Approximately 300 Feet
B-10
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Figure B-l 1 . Typical Examples of Crickets
B-12
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Figure B-]2. Three Examples of Maximum Spectra of
Birds and One of a Squirrel
B-13
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Figure B-13. Some Examples of Dogs
B-14
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APPENDIX C
TERMINOLOGY
This Appendix contains descriptive definitions of some of the principal terms used in
this report. For additional definitions refer to American Standard Acoustical
Terminology, SI. 1-1960, Revision of Z24. 1-1951 and including Z24.1a, American
Standards Association, May 26, 1960.
SOUND PRESSURE
The sound pressure at a point is the total instantaneous pressure at that point in the
presence of a sound wave minus the static pressure at that point.
LEVEL
In acoustics, the level of a quantity is the logarithm of the ratio of that quantity to a
reference quantity of the same kind. The base of the logarithm, the reference quantity,
and the kind of level must be specified.
Note 1: Examples of kinds of levels in common use are electric power level, sound-
pressure-squared level, voltage-squared level.
Note 2: The level as here defined is measured in units of the logarithm of a refer-
ence ratio that is equal to the base of logarithms.
Note 3: In symbols,
L = Iogr(q/q0)
where
L = level of kind determined by the kind of quantity under consideration,
measured in units of logrr
r = base of logarithms and the reference ratio
q = the quantity under consideration
qQ = reference quantity of the same kind
Note 4: Differences in the levels of two like quantities q-| and c\2 are described by
the same formula because, by the rules of logarithms, the reference quantity is auto-
matically divided out:
C-l
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DECIBEL
The decibel is one tenth of a bel. Thus, the decibel is a unit of level when the base
of the logarithm is the tenth root of ten, and the quantities concerned are proportional
to power.
Note 1: Examples of quantities that qualify are power (any form), sound pressure
squared, particle velocity squared, sound intensity, sound-energy density, voltage
squared. Thus the decibel is a unit of sound-pressure-squared level; it is common
practice, however, to shorten this to sound pressure level because ordinarily no
ambiguity results from so doing.
Note 2: The logarithm to the base the tenth root of 10 is the same as ten times
the logarithm to the base 10: e.g., for a number X , log]0l/lo X ~ 10 logigX^ =
20 log]QX. This last relationship is the one ordinarily used to simplify the
language in definitions of sound pressure level, etc.
SOUND PRESSURE LEVEL
The sound pressure level, in decibels, of a sound is 20 times the logarithm to the base
10 of the ratio of the pressure of this sound to the reference pressure. The reference
pressure is 20 micronewtons per square meter.
ONE-THIRD OCTAVE BAND SOUND PRESSURE LEVEL
The one-third octave band sound pressure level of a sound for a specified frequency
band is the sound pressure level for the sound contained within the restricted band.
SOUND LEVEL (NOISE LEVEL)
Weighted sound pressure level measured by the use of a metering characteristic and
weighting A, B, or C, as specified in this standard. The weighting employed must be
indicated, otherwise the A-weighting is understood. The reference pressure is 20
micronewtons per square meter (2 x 10~4 microbar). Unit: decibel (dB). In this report
sound level (noise level) is always A-weighted.
STATISTICAL LEVELS
Any of the statistical noise levels is given in terms of the value of the noise level
which is exceeded for a stated percentage of the time period during which the measure-
ment was made. The symbol for the noise level which is exceeded y percent of the
time is Lv.
The most common measures utilized in this report are \-y<}, L9Q, L^Q, L^Q and L], which
denote the value of the noise level which is exceeded 99, 90, 50, 10, and 1 percent
of the time respectively.
C-2
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ENERGY EQUIVALENT NOISE LEVEL
The energy equivalent noise level for a stated period is the level of a constant, or
steady state, noise which has an amount of acoustic energy equivalent to that con-
tained in the measured noise. The symbol for the energy equivalent noise level is
L . Its mathematical definition is
Leq - 10 log
NL
_j_ / ,„'
10
11-
_J_ f
'2-h J
fi
10 *
where NL is the measured noise level as a function of time and t] and \2 denote the
times at the beginning and ending of the measurement period.
RESIDUAL NOISE LEVEL
The residual noise level is the level of the all encompassing unidentifiable noise which
remain after all identifiable noises have been eliminated. For this report LQQ has been
used as an estimate of the residual noise level when no steady state identifiable noises
were known to be present.
NOISE EXPOSURE AND NOISE LEVEL SCALES
"Noise exposure is the integrated effect, over a given period of time, of a number of
different events of equal or different noise levels and durations. " The integration may
include weighting factors for the number of events during certain time periods in which
people are more annoyed by noise (e.g., sleep interference by noise at night).
The various scales for noise expsoure or noise level in use throughout the world differ
according to the particular method of integration or summation, time period weighting
factors, or frequency weightings.
The following summarizes the essential features of and correlation between three noise
scales currently used in the United States for noise exposure from aircraft noise. The
correlations are necessarily approximate, but are considered valid for interrelating
evaluations of aircraft noise exposure at major airports served by current commercial
jet aircraft. The definitions used herein are not always the same as those formally
given in the source references. In all cases, however, the simplified form given here
is an exact equivalent or valid approximation thereto.
C-3
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Noise Exposure Forecast (NEF)
A method currently in wide use for making noise exposure forecasts utilizes a perceived
noise level scale with additional corrections for the presence of pure tones. Two time
periods are used to weight the number of flights (Galloway, W.J. and Bishop, D.E.,
"Noise Exposure Forecasts: Evolution, Evaluation, Extensions and Land Use Inter-
pretations, " FAA-NO-70-9, August 1970).
The single event noise level is defined in terms of effective perceived noise level
(EPNL) which can be specified approximately by:
where
EPNL = PNL + 10 log + F, EPNdB
max 20
PNL = maximum perceived noise level during flyover, in PNdB,
max
t,n - 10 dB down duration of the perceived noise level time history,
in seconds,
and F = pure tone correction. Typically, F~ + 3dB
Community noise exposure is specified by the quantity, noise exposure forecast (NEF).
For a given runway and one or two dominant aircraft types, the total NEF for both day-
time and nighttime operations can be expressed approximately as:
NEF = EPNL + 10 log Nf - 88.0
where
EPNL = energy mean value of EPNL for each single event at the point in
question
Nf = (NJ + 16.7Nn) or
= (15n' + 150"^ )
a n
NJ, n = total number and average number per hour, respectively,, of flights
during the day period 0700 to 2200.
N , ?T = the total number and average number per hour, respectively, of
" flights during the night period 2200 to 0700.
The constant (-88.0) dB includes an arbitrary -75 scale-changing constant and
a reference number of daytime flights of 20. The constant 16.7 accounts for
the 10-to-l weighting factor for flights during the 9-hour night period.
C-4
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Composite Noise RaHng Method (CNR)
The original method for evaluating land use around civil airports is the composite noise
rating (CNR). It is still in wide use by the Federal Aviation Administration and the
Department of Defense for evaluating land use around airfields (Civil Engineering
Planning and Programming, "Land Use Planning with Respect to Aircraft Noise, "
AFM 86-5, TM 5-365, NAVDOCKS P-98, October 1, 1964). This noise exposure
scale may be expressed as follows:
The single event noise level is expressed (without a duration or tone correction) as
simply the maximum perceived noise level (PNLmax) in PNdB.
The noise exposure in a community is specified in terms of the composite noise rating
(CNR), which can be expressed approximately as follows;
CNR = PNL + 10 log N-- 12
max ° f
where
PNL - approximate energy mean maximum perceived noise level (PNL) at
max . .
a given point
N, = same as defined for NEF. The actual method for accounting for
the number of flights and time periods uses discrete interval correc-
tion factors. These have been approximated by the use of the
equivalent continuous weighted number of flights, Nr.
Community Noise Equivalent Level (CNEL)
The following simplified expressions are derived from the exact definitions in the report,
"Supporting Information for the Adopted Noise Regulations for California Airports."
They can be used to estimate values of CNEL where one type of aircraft and one flight
path dominate the noise exposure level.
Single event noise is specified by the single event noise exposure level (SENEL) in dB
and can be closely approximated by:
SENEL - NL + 10 log., t , dB
max a!0 ea
where
NL = maximum noise level as observed on the A scale of a standard
sound level meter
and
t - effective time duration of the noise level (on A scale) in seconds
C-5
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The effective duration is equal to the "energy" of the integrated noise level (ML),
divided by the maximum noise level, NLmax, when both are expressed in terms of
antilogs. It is approximately 1/2 of the 10 dB down duration, which is the duration
for which the noise level is within 10 dB of
A measure of the average integrated noise level over one hour is also utilized in the
proposed standard. This is the hourly noise level (in dB), defined as:
HNL-SENEL + 10 log n - 35.6, dB
where
SENEL - energy mean value of SENEL for each single event,
and
n = number of flights per hour
The total noise exposure for a day is specified by the community noise equivalent
level (CNEL) in dB, and may be expressed as:
CNEL = SENEL + 10 log N - 49.4, dB
C
where
or = (12 n . +9n +90n )
d e n
N ,, n i = total number and average number per hour, respectively, of flights
during the period 0700 to 1900
N , n = total number and average number per hour, respectively, of flights
& 6 during the period 1900 to 2200
and
N , n - total number and average number per hour, respectively, of flights
" n during the period 2200 to 0700
An alternative form of Community Noise Equivalent Level (CNELo) used in Section 5.1
employed the time period weighting factor from the Noise Exposure Forecast method.
It is approximated as:
CNEL2 = SENEL + 10 log Nf - 49.4 dB
where Nr was given previously for NEF calucation.
C-6
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COMPARISON OF COMPOSITE RATING SCALES FOR SPECIFYING COMMUNITY
NOISE EXPOSURE
The basic expressions defined above for specifying community noise exposure are
summarized below.
Noise Exposure
Forecast
NEF = EPNL + 10 log Nf - 88, dB
Composite Noise
Rating
Community Noise
Equivalent Level
and
CNR = PNLmax + 10 log Nf - 12, dB
CNEL = SENEL + lOlogN - 49.4, dB
CNEL2 = SENEL + 10 log Nf - 49.4, dB
OU.S GOVERNMENT PRINTING OFFICE 1972 484-483 (111) 1/3
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-Oil SGEUCY
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