CENTER FOR A QUIET ENVIRONMENT
NOISE MEASUREMENT WORKSHOP
1981
Prepared by:
Jim Buntin, Director
Center for a Quiet Environment
U.C. Richmond Field Station
1301 So. 46th Street, Bldg. 167
Richmond, CA. 94 8 04
(415) 231-9463
EPA Region IX
Technical Assistance Center
-------
CENTER FOR A QUIET ENVIRONMENT
NOISE MEASUREMENT WORKSHOP
OUTLINE
I. Fundamentals of Noise
A.
Definition
B.
The Decibel
C.
Sound Pressure Levels
D.
Frequency and Wavelength
E.
Loudness
P.
Weighting Networks - The "A" Scale
G.
Attenuation with Distance
H.
Effects of Atmospheric Conditions
I.
Vegetation Effects
J.
Barriers and Walls
II. Measurements
A. The Sound Level Meter
B. Chart Recordings
C. The Histogram
E(n) Valuesj ^eq> and Lqsha*
E. Composite Noise Scales
1 Ldn and CNEL
2. SEL and SENEL
3. Nf = Nd + 3Ne + 10Nn
III. Ordinance Schemes
A. "Ambient" + 5 313
B. Leq
C. Time-weighted
D. Receiver vs. Emitter Standards
-------
Page Two
E. Others
IV. Land Use Standards
A. Leq (2^0
B s.nd CNIHIj
c Lmax
D. Lio
V. Transportation Noise Prediction
A. Highway Traffic
B. Railroad Operations
C. Airport Operations
VI. Field Measurements
A. Histograms, L(n)ป Leq
B. Octave-band analysis
c * Lmax
-------
CENTER FOR A QUIET ENVIRONMENT
NOISE MEASUREMENT WORKSHOP
Fundamentals of Noise
A.
DEFINITION
Noise is unwanted or annoying sound. Sound is defined as
any pressure variation that the human ear can detect.
The range of human
hearing is 20 Hz to
20,000 Hz.
B,
THE DECIBEL
Sound is measured on the decibel scale, with the decibel
relative to A defined as
o
dB = 10 log _A_
A
C. SOUND PRESSURE LEVELS
A sound level, in its simplest form, is expressed by the term
SPL = 10 log (P1/PQ)2
when dB is relative to pQ = 20^Pa (micropascals) where p1 and pQ
are two sound pressures.
i
-------
Decibel Addition:
Sound levels cannot be arithmetically added because decibels
are logarithmic units. If several levels of equal value are to
be added, add as follows:
No. of Equal Add to That
Values Level
2 3 dB
3 5 dB
4 6 dB
5 7 dB
6-7 8 dB
8 9 dB
9-10 10 d3
N 10 log N dB
D. FREQUENCY AND WAVELENGTH
The number of pressure variations per second is called
frequency of sound and is measured in cycles per second or Hertz (Hz).
The physical distance from one wavetop to the next is referred to
as wavelength. Wavelength can be determined if speed and
frequency of sound are known:
Wavelength = Speed/Frequency
The following frequencies produce the following wavelengths:
Frequency
(Hz)
20
31
63
125
250
500
1000
2000
4000
8000
14000
Wavelength
(ft)
55
35
17.5
9
4.5
2.2
1.1
55
27
.14
.08
In order to determine the frequency distribution of a noise,
it can be passed successively through different filters to separate
the noise into octaves on a frequency scale. The following table
shows the nine standard octave bands.
ii
-------
Octave
Frequency
Range
(Hz)
E.
P.
22
44
88
175
350
700
1400
2800
5600
LOUDNESS
44
88
175
350
700
1400
2800
5600
11200
Geometric
Mean Frequency
of Band
(Hz)
31
63
125
250
500
1000
2000
4000
8000
WEIGHTING NETWORKS THE "A" SCALE
The frequency response of the A-scale filter Is as follows
Octave
Frequency
Band
(Hz)
31
63
125
250
500
1000
2000
4000
8000
A-Scale
Frequency
Response
(dB)
-39
-26
-16
-9
-3
0
+1
+1
-1
G. ATTENUATION WITH DISTANCE
The inverse square law states that as sound from an essentially
localized source travels away from that source, the sound level
drops off as follows:
point source = 6 dB/doubling distance
iii
-------
AD
Where X is the point source, at distance D, the area of the
segment within the radiating lines is a x b or A. At distance 2D,
a has increased to 2a and b has increased to 2b. The area at 2D
is 4 times the original area at D, or bA. The energy per unit area
at distance 2D is one fourth that of D.
line source = 3 dB/doubling distance
H. EFFECTS OF ATMOSPHERIC CONDITIONS
The effects of weather conditions on noise propagation are
extremely difficult to predict because of the very large number of
different atmospheric conditions that may have an effect on
propagation. When noise travels over considerable distances through
the atmosphere, the sound pressure level received may vary as much
as 25 dB depending upon wind direction, temperature inversions,
precipitation, and other variables. Also, the sound pressure level
will often fluctuate over short periods of time. Thus community
noise measurements are normally done under calm and stable weather
conditions in order to get the most conservative and consistent
readings.
Wind and temperature gradients may cause "shadow zones" where
the sound is bent upwards, but these effects are very complex and
difficult to predict. On a clear sunny day with winds as low as
10 mph, the excess attenuation at a given point upwind may be 20 dB
higher than for the same distance downwind.
The presence of fog or precipitation normally reduces the excess
attenuation because wind and temperature gradients tend to be small
under these conditions. Also, there is some laboratory evidence that
fog may provide increased attenuation above that predicted for
molecular absorption.
Sound traveling through air loses energy from the effects of
heat conduction and radiation, viscosity, diffusion, and from
molecular absorption. In most cases, molecular absorption is the
process causing the major loss of sound energy in noise control
problems. In calculations to determine the amount of sound
absorption in air, the frequency characteristics of the sound, the
air temperature, and the humidity are important factors. For
example, for sounds with major frequency components in the center
of the audible band, the excess attenuation due to molecular
absorption will be about 5 dB for distances of about 2000 feet.
iv
-------
I. VEGETATION EFFECTS
Absorption or attenuation of sound traveling over the earth's
surface depends upon the structure and covering of the ground, and
upon the heights of the source and the receiver. Attenuation data
have been developed for general cases, usually with the assumption
that the sound is traveling parallel to the earth's surface, less
than 10 feet above low ground (for shrubs and grasses) or less than
30 feet above high cover (for trees).
Generally, ground covered by shrubs and grasses is considered to be
acoustically "soft" or absorptive, and is responsible for excess
attenuation. In highway noise modeling, a 4.5 dB/DD attenuation
rate is usually assumed for such surfaces. The presence of trees
is usually of more significance psychologically than physically,
as approximately 100 feet of dense forest are required to achieve
a 5 dBA noise reduction. High frequency sounds are much more
readily attenuated by trees, however. Recent research has shown
that the presence of trees on top of noise-attenuating berms or
roadcuts can "scatter" or diffract high-frequency sound downward
over a barrier, thus compromising the effectiveness of the barrier.
J. BARRIERS AND WALLS
Long distance outdoor sound propagation is affected by surface
reflection and by reflections from, transmission loss through, and
diffraction around barriers in the sound propagation path. However,
as a general rule the losses in propagated soundฆ levels are signi-
ficant only if either the sound source or the receiver is closer to
the barrier than about 10 times the maximum dimension of the barrier.
In an area where there are strong reflections (a highly reverberant
sound field) sound levels may remain the same or even increase as
the distance between the source and receiver are increased.
Reflections from the earth's surface may also increase the
levels of sound propagation but this effect is generally less than
2 dB over flat ground surfaces and it is extremely complex to predict
over large distances. Generally a hard smooth surface such as
concrete, asphalt, or packed dirt must cover more than half of the
distance between the observer and the sound source for the level to
be raised by as much as 2 dB.
The attenuation of sound provided by a barrier depends upon the
density and the physical size of the barrier, and upon the spectrum
of the sound source. The propagation of sound through or around a
barrier also depends upon the acoustical environment on both sides
of the barrier. As a general rule, the transmission loss provided
by a barrier will increase with increasing density of that barrier.
However, atmospheric scattering imposes a practical limit of about
24 dB on the reduction in A-weighted sound level that can be expected
from a barrier. Ground contours and covers can of course change
these limits significantly in some cases.
v
-------
Refer to the following nomograph (pp. 2-3) for an approximate
method of calculating barrier effects on highway noise. A more
detailed method is presented in the publication: FHWA Highway
Traffic Noise Prediction Model, FHWA RD-77-10 8.
vi
-------
FIGURE I.I CHART FOR COMBINING SOUND LEVELS BY "DECIBEL ADDITION"
FIGURE 1.2 ELECTRICAL FREQUENCY RESPONSE SPECIFIED FOR THE A-SCALE
FILTER OF SOUND LEVEL METERS (ANSI SI.4-1971)
1
-------
SECTION 1
SIMPLE PROCEDURE TO
EVALUATE A GIVEN BARRIER
1. Get, by any convenient means, the
values of the following quantities:
h, the height of the barrier above
the line-of-sight from source to
observer (feet); R and D, the slant
distances, along the line-of-sight,
from the barrier to the source and
observer, respectively.*
2. Enter Chart A of Figure 1 with the
value of h on the left-hand scale;
move right to intersect the curve
corresponding to R (or D, whichever
is smaller).
Observer
Barrier
3. Move down to Chart B, to intersect the curve corresponding to the
value of D/R (or R/D, whichever is larger).
4. Move right to intersect the scale of Chart C, to find the value for
the barrier shielding in decibels.
Note: Use a source height of 2' above the roadway for autos, 8' for
trucks and 15' for diesel locomotives.
The effective distance from the source to the receiver may be
calculated by entering Figure 2.
* Specifically, R and D are the two segments into which h breaks
the line-of-sight.
-------
30
20
15
10
8
6
5
4
3
2
1.5
1
0.8
0.6
0.5
0.4
0.3
0.2
0.15
NOMOGRAM FOR CALCULATING BARRIER ATTENUATION
(0
J
w
a
H
u
ง
Figure 1
3
-------
1
I
I
-------
T
I I L Hi MIN H 1 1 1 1 I J
STEADY STATE INTERMITTENT SOUND
FIGURE 10,2
-------
8 AMBIENT -
i
i
j
-------
i i i fcj MIN d - i - i i i i 1
FLUCTUATING INTERMITTENT SOUND
FIGURE 10.1
-------
1 1 1 I I
1 1 1 1
1 I I 1 1 1 1 1 1 1
5 SEC.
IMPULSIVE SOUND
FI6URE 10.5
-------
COMPOSITE COMMUNITY NOISE METRICS
Community Noise
Equivalent Level
CNEL
SENEL + 10 Log Nc - 49.4, dB
10 Log
lD
12 iff 3
10 + -10
24 24
Lg+5
"To"
+ -10
24
Lfl+10
10
,dB
Day-Night
Average Level
I-dn - SENEL + 10 Log Nl - 49.4, dB
10 Log
15
lD
Ljj+10
1010 + 10 10
24
24
,dB
Where SENEL * Average Single Event Noise Exposure Level
T L(t)
" 10 Log
10
10 dt
0
ปdB
^aax + 10 1-08 *
ea
where t
ea
*10
end t t
10
(triangular wave form - moving
"point" source)
(rectangular wave form - moving
"line" source)
&
+ 1,08 n (moving point source)
V
-------
-2-
and L ฆ maximum A-weighted source level during pass-by
max
t..ป 10 dB down duration (time in sec that source level
is within 10 dB of L)
UlflX
R ซ Perpendicular distance from source to observer; feet
Source velocity; feet/second
Energy Equivalent Level, L :
eq
10 Log
1
T
L(t)
10
10 dt
,dB
where T is normally taken as 60 minutes
and L_, Lp,, L ฆ Average Energy Equivalent Levels
(Le<1) for Day, Evening, Night:
Day (CNEL) 0700 - 1900
Day (Lda) 0700 - 2200
Evening 1900 - 2200
Night 2200 - 0700
10
-------
-3-
N^, ฆ Equivalent number of single event intrusions for CNEL
N. + 3N + 10 N
a e n
ฆ Equivalent number of single event intrusions for
N. + 10 N
d n
where N^, Ng, Nn ป number of events occurring
during day, evening, and night
Approximate Relationship to other Composite Metrics:
CNEL = Ldn* NEF + 35 - CNR - 35
//
-------
relationship of l to statistical noise metrics
eq
Definitions:
^101 Noise level exceeded 10% of sample period, dBA
L50: Noise level exceeded 50% of sample period, dBA
Lgo' Noise level exceeded 90% of sample period, dBA
Of : Standard deviation (Arithmetic)
For Normally Distributed Noise Events:
Leq " L10 - 1,28 a + 0,115 adB
- Lso + .115 <72, dB
For Highway Noise, Given a in the range of 2 - 5 dB, the Following
Approximation may be Used:
hq ' L10 " 2 dB' ฑ 2 dB
where L,g is based upon the peak hourly flow period which
typically constitutes 10% of the ADT.
Noise Pollution Level, NPL:
NPL - Leq + 2.56 0, dB
i L30 + (l10 - z90) + (L10 - L90)!, dB
57
Traffic Noise Index, TNI:
TBI - 4 (L10 - l90) + l90 - 30, dB
n
-------
Ll
5-
ChMlhT>oป UDJll
-------
SฃL chcul >\ t > o f/s:
/4/.^cKrtry pLIOVi'-
SEY-= + io^lo^ -ฃ } c\-S W^?r< ~ "t~ dufik"ttcปv a-f e,ve^
= It,.? +ฆ )0 Ja^
= ฐltป.? + }/-ฆ%
- logs
- $11
L-y^ook 10 ~^to~) l*/Ue* - 5=5 "ฐ/z
== 100 H- )0 Aoq '^z (^fo>r 4v\o,v>CjU^ov e.vje.wf^
S itpo + 8,6
= /{8) "3?
14
-------
"MEASUREMENT AND ANALYSIS OF EHVIRONtE STEAL NOISE
AND COMMUNITY RESPONSE"
Notes on Proper Noise Measurement Technique
1. The following weather information should be noted and recorded on
data sheet:
Temperature
Relative humidity
Wind velocity and direction
If extended measurement, variation over sample time should be noted.
2. Measurement location, site layout.
Sketch site layout and proximity to source. Note all significant
distensions, topographic details, relative lights of source and
measurement position, presence of foliage (if significant, note
density and type of growth). Also note ground cover in immediate
proximity of measurement position and between source and measure-
ment location.
3. Select appropriate microphone: Either free or diffuse field
(random incidence). Orient SLM accordingly; i.e., microphone
should be perpendicular to the line of sight from source to ob-
server or pointed at the source.
4. Always calibrate before and after measurement (if long-term,
intermittent calibrations are appropriate).
5. Check batteries - before and after measurement (during, if
questionable). Batteries are cheap! Replace them.
is
-------
2-
6. Always use windscreen for outdoor measurements. Curtail measurement
when wind velocity exceeds approximately 12 mph. (You may check for
wind overload by looking at C and A scale levels. Often the A-
weighted level may be on scale, but the C-weighted level will be
off-scale, indicating meter overload due to wind.)
7. Proper microphone height: 4-5 feet above ground level is standard.
Note exact height used on data sheet. (You may want to check noise
levels at second story heights, etc. Note all measurement heights
used on data sheet.) Use of a tripod is preferred practice.
8. Reflecting objects. Ten feet or more separation from reflecting
objects is recommended where possible. When closer, note on the
data sheet.
9. Distance from source. Stay out of the near fieldl Typically,
measurements should be taken no closer than the largest major source
-J u-t en -c- - _ . u - c
*ซ! w vvt4i WW ซ/W 4CC W Xi UlU W CUkCL ii.UC UL
the outermost traffic lane is standard. Railroads; 100 feet from
track center line. Other distances as appropriate for specific
cases; i.e., receptor's property boundary, outside receptors window,
receptors patio, etc. Try to measure at positions where receptor
would realistically be exposed to noise.
10. Meter ballistics.
Typically, use A-weighted filtering on "slow" response for most
community noise work. (Averaging time is approximately 1 second.)
Use A-weighted "fast" to evaluate impulsive sounds or quickly varying
events. (Note: These readings will be different from peak impulse
levels as measured with an "impulse meter".)
11. Meter Scale - Measurement Range.
Set attenuator so that readings are made as near mid-scale as possible.
This insures maximum readability and minimizes chances of overloading
meter.
n
-------
-3-
12. Reading the Meter.
Stand away from the meter (or hold It at arms length) to avoid inter-
ference effects of your body. Headphones are recommended to detect
overload (from wind, passby peaks, etc.) and to detect any peculiar-
ities in the noise measurements.
13. Interior Measurements.
When determining interior noise levels, measure at several locations
and varying heights around the room. The reported sound level should
be the arithmetic average of these readings.
14. Background Noise.
Noise from extraneous sources can mask the noise level you wish to
measure. This background noise should be at least 10 dB below the
source level in order that only the source level is measured. If
the difference between the source level and the background noise
is 6 dB or greater, then the level of the source itself can be
reasonably determined by subtracting a small correction which
vould account for the contribution of the background noise to the
overall level measured. The following table may be used for back-
ground noise level corrections.
Difference Between Total Noise
and Background Noise,
dB
Amount to be Subtracted
from Total Noise,
dB
6-8
1.0
0
H
1
00
0.5
> 10
0
It
-------
COMMUNITY
NOISE
FUNDAMENTALS
A
TRAINING
MANUAL
18
-------
Chapter 11
INSTRUMENTATION AND DATA ANALYSIS
Definitive community noise ordinances are written in terms of the
maximum sound levels permitted. Various measurement descriptors have been
developed to express these limits, but in almost all cases an A-weighted
frequency response is used. If an ordinance specifies a maximum sound
pressure level limit, measurements can be made directly with a sound level
meter (SLM). If the ordinance specifies an average reading, this too can
be obtained easily from SLM readings if, the noise levels are constant over
reasonably long periods of time. An average kind of measurement is
extremely difficult to obtain, however, if the noise levels vary unpredict-
ably with time.
Statistical or averaging equivalent assessments are often required if
complex noises must be measured. Two such descriptors are the A-weighted
energy equivalent sound level, Leq, and the 24-hour day/night energy
equivalent level, L
-------
Figure 11.1 Basic Sound Level Meter.
in the USA, and for the two types of sound level meters (Precision Type 1,
and General Purpose Type 2) recommended for community noise measurements.
There are several new- special-purpose sound level meters designed for
direct reading in energy equivalent levels, Leq, that provide averaging
times ranging from 1/8 second to 24 hours. Some have a standby or pause
control to stop integration for a given time period.
20
-------
11.1.1 Weighting Networks
Sound level meter frequency weighting networks were originally intended
to provide reasonable correlations between meter readings and loudness.
They are also used to determine roughly how sound energy is distributed with
frequency. In community noise measurements the most often used A-weighting
gives good correlation with human response. Differences between the
A-weighted and C-weighted (or flat-weighted) levels afford a good approxima-
tion of the ratio of high-to-low frequency distribution of the sound.
The ideal A-, B-, and C- frequency weightings, relative to a flat or
overall frequency response, as specified by ANSI SI.4-1971 are shown in
Figure 11.2. Tolerances may be found in the Specifications. The O-weighting
network, which emphasizes frequencies between 1000 and 10,000 Hz, is included
in certain foreign sound level meters and is used primarily for noise
measurements around airports.
11.1.2 Meter Indication and Response
The indicating meter or readout of the SLM must have a scale covering
a range of at least 15 dB. The accuracy of the scale gradations must be at
least ฑ 0.2 dB except in the lower part of the scale that is overlapped by
a change in attenuator setting where the accuracy requirement is ฑ 0.5 dB.
The response time of the indicator (generally measured as the response time
of the complete SLM) must be in accordance with the "Fast" or "Slow" dynamic
characteristics specified. The Fast response specifications require the
meter to be within 0 to 4 dB less than the correct reading for a Type 2
instrument and 0 to 2 dB less than the correct reading for a Type 1 instru-
ment for a 1000 Hz signal with a duration of 200 milliseconds. The slow
response specifications require the meter to be within 2 to 6 dB less than
the correct reading for a Type 2 instrument and 3 to 5 dB less than the
correct reading for a Type 1 instrument for a 1000 Hz signal with a duration
of 500 milliseconds.
If sound level fluctuations are rapid but of a duration of 500 milli-
seconds or longer, the SLM may be used with reliable accuracy. With the
exception of impulsive sounds, most community noises may be measured with
the fast or slow meter characteristics. Fast meter characteristics should
be used wherever possible for the greatest accuracy; however, when the
sound levels are fluctuating rapidly, it may be necessary to use the slow
meter characteristics to get reproducible readings. The slow response
averages the sound Input so that there are smaller ranges of level change
and the rates of change are reduced so that the meter can be read more
accurately. The slow response is particularly useful when widely fluc-
tuating sound levels are to be compared from one time to another (i.e.,
before and after noise control measures). If the sound level is fluctuating
6 dB or less a subjective judgment of central tendency is usually acceptable.
If the sound level is fluctuating more than 6 dB, manual or automatic
sampling of sound levels may be required. Manual sampling requires less
equipment, but it requires the presence of a data taker. The more expensive
automatic field-type sampler will usually operate by itself once it is
calibrated and set up in a selected location. Manual sampling procedures
are described in Section 11.3.
Z/
-------
Frequency
Figure 11.2 Relative response for A, B, C, and D weighting.
-------
When impulsive sounds such as those from gun shots, pile drivers, drop
forges, or jack hammers, are encountered, an oscilloscope or an impulsive-
type SLM must be used (3,4,5). Impulsive sounds are considered to be those
whose sound pressure levels rise above the ambient by 10 dB or more in a
time less than 0.2 second. The measuring instrument must be capable of
reading the peak sound pressure level (unweighted). If an impulsive-type
SLM is used, it should include a peak detector and holding circuitry so
that the peak level is held long enough to be read or until manually reset.
Peak sound pressure levels should be recorded for at least 10 impulses in
close succession so that a numerical average level can be determined.
Generally, the average, the highest, and the range of impulsive levels should
be recorded. Extreme care must be taken to follow the instrument manufac-
turer's instructions so that accurate impulse sound level data can be
obtained.
11.1.3 Microphones
Each type of microphone has advantages and disadvantages that depend
upon the specific measurement requirements. Calibration and frequency-
response curves, and stability characteristics with respect to temperature,
humidity, vibration, and electromagnetic fields are generally available
from the instrument manufacturer. Performance limitations for the micro-
phone system may be found for Types 1 and 2 sound level meters in ANSI
SI.4-1971.
Orientation: Some microphones are calibrated to perform correctly when
sound approaches perpendicular to the diaphragm (0ฐ), while others are
calibrated for grazing incidence (90ฐ), or for random incidence. Figure
11.3 shows the microphone response for these different angles of incidence.
Any microphone must be oriented as specified in the manufacturer's instruc-
tions; otherwise errors will result that will be particularly prominent
at high frequencies. The most frequently specified orientation is illus-
trated in Figure 11.4. The preferred height of the microphone above the
ground or supporting surface is 1.2 meters (4 feet), although any height
between 0.6 and 1.8 meters (2 and 6 feet) is acceptable for specific
measurement conditions. A record of microphone position should be care-
fully documented, preferably on a plan view of the measurement site so that
measurements can be repeated at a later date if necessary (see Figure
12.1)2.
The choice of a microphone may depend upon several factors, including
the location of the sound source. If the sound is coming from a particular
fixed direction, a microphone calibrated at perpendicular incidence (free
field type) may be selected because it will discriminate against potential
masking noises coming from other directions and generally it will have
very good high frequency response characteristics. If, on the other hand,
the source is in motion, such as in the case of a vehicle travelinq on a
road, a microphone calibrated for grazing incidence (pressure-type) may
be preferred because it can be mounted in a fixed position pointing upward
^Additional calibration data should be recorded when using the SLM in a
noise survey. Figure 12.1, the Community Noise Survey Data Sheet,
provides a simple form for such record keeping. The appropriate procedure
for completing this data sheet is described in Chapter 12.
-------
dB 20
10
-4>
0
-10
-20
r"
-
....- -
_
r
.
_
-
-
--
-
-
-
--
-
-
-
---
--
nz
_
-
i
_
-
-
-
_
-
-
-
-
-
ฆ
-
--
-
-H~n
it
-
--
-
-
-
HI
-
~
-
-
-
-
-
-
-
-
.1
-
1
"-I
_11
Z_
-
...
ii
-
-
-
-
-
- -
.
[
-
-
-
-
-
-
-
_
-
-
y
H_1
-
...
_
c\
_
>
i
_
_
_
-U
I11H1
-
-
-
-
\
--
--
--
-
_
if
-RANDC
' -
-
-
-
_
_
ii
:
-
-
1
?!
HI
n:
i:
-
:
:-
y
"
-
-
90
ฐ1H
~
---
'
...
-
in:
.11.
-
--
--
HI
1.
-
i
\
--
-- .
ฆH
FREE FIELD RESPONSE OF A 1"
PRESSURE
-
111
MICROPHONE FOR VARIOUS ANGLES OF
---
-
-
-
-
-
--
INCIDENCE.
"
...
:n.
-
-
---
r
I
;
1
~r\
hi;
in:
--
-
HI
inn
H.
6
2
~u
....
-
-
H
1
HI
w
\
7ฐ
-
-
-
-
1
__
_
-
-
~
-
-
:
HI.
10 90 Hz 50 100 200 600 1000 2000 5000 10000 20000 40000
Figure 11. 3
-------
Figure 11.4 The sound level meter should be oriented with respect to the
source of sound as recommended in the SLM instruction manual for the micro-
phone being used. Most microphones should be pointed at a right angle to
the sound path as shown here.
and receive the sound at grazing incidence as the vehicle moves. The
microphone calibrated for random incidence is generally a good choice for
measurements in a diffuse sound field where the sound is coming from all
directions. These microphones may be used interchangeably in most situa-
tions% but the manufacturer's instructions must be followed on orientation
in each situation or errors will result.
Temperature and Humidity: Most modern microphones are not permanently
damaged by normal ranges of temperature and humidity. However, temporary
erroneous readings may result from condensation if the microphones are
moved from very cold to very warm areas. To avoid errors from condensation,
the instruments should be turned on and allowed to sit in the measurement
area for at least five minutes prior to making measurements. Temperature
and humidity correction curves are generally supplied with the microphone
and should be consulted.
Microphone Cables: In most community noise assessment situations,
sound level measurements should be made with the microphone mounted on the
sound level meter. However, there are special situations where an operator's
body, or even the instrument case, should be removed from the measurement
area to obtain accurate data. In most cases where cables are required the
sound has a high proportion of its energy concentrated in high frequencies
(above 1000 Hz). The higher the frequencies of major sound components the
-------
more likely it is that there will be errors introduced as the result of
reflection from the operator's body or from the instrument case.
When extension cables are required for microphones, care must be taken
to make the necessary corrections to the sound level reading according to
the instrument manufacturer's instructions. Some microphones require special
electronic circuitry when used with cables and others do not. The amount of
correction for given lengths of cable also varies from one instrument system
to another. Therefore, the manufacturer's instructions should be
followed precisely. Finally, the microphone must always be calibrated while
it is mounted on the cable before and after it is used.
Windscreen: Rapid air movement over a microphone causes turbulence that
in turn generates extraneous noise. This noise can effectively mask the
sound being measured and cause erroneous high level readings. The use of
earphones connected to the SLM output jack (consult manufacturer's recommen-
dations) often will enable the operator to detect wind-generated noise;
however, low level masking may occur that will be inaudible. Therefore, it
is good practice to use microphone windscreens in any case when wind or wind
gusts are_suspected during the course of measurements.
Generally, windscreens are either spherical or cylindrical shaped
open-celled polyurethane, or silk-covered grids. The windscreens are
attached directly over the microphone so that the effects of wind are reduced.
However, there are limits to their effectiveness. Three rules-of-thumb are:
1) measurements should never be made, even with windscreens,
in winds having velocities greater than 20 km/hr (12 mph);
2) measurements should not be made if wind noise is audible
through a monitoring headset connected to an SLM when
using'the A-weighting and the lowest attenuator setting
(setting for measuring the lowest sound level to be
measured);
3) measurements may be made utilizing a windscreen and an
octave, or narrower, band analyzer as long as it can
be determined that the wind noise remains at least 10
decibels below the sound being measured in any of the
frequency bands.
In all cases, the windscreen should be one provided by the SLM manu-
facturer for that instrument. Corrections should be available for these
windscreens. If such a windscreen is not available, if no corrections are
available for a windscreen, or if a windscreen is old or soiled, tests
should be made by presenting reproducible sounds to the microphone with and
without the windscreen in place. The test sounds used should contain
low, medium, and high frequency components (i.e., 500, 1000, 2000, 4000, and
8000 Hz). In particular, the windscreen should be tested with similar
frequency components to those expected from the sounds to be measured.
Corrections should be developed and used for differences up to 2 dB. If
the windscreen causes changes greater than 2 dB, the windscreen should be
discarded.
26
-------
11.1.4 Calibration
There are two kinds of instrument calibration procedures that must be
used to insure that accurate measurements are obtained. A laboratory
calibration should be performed at regular intervals not wider spaced than
one year. These calibrations should be done by the instrument manufacturer
or qualified personnel at acoustical laboratories. Equally important field
calibrations should be made before and after each use of the measurement
equipment. Field calibrations are conducted with acoustic calibrators pro-
vided by the instrument manufacturers.
Generally, the field calibrators are compact, battery operated devices
that provide.a means for conducting an overall system calibration check.
Some calibrators generate a single frequency and others provide several
different test signals, all at specified sound pressure levels. Field
calibrators are designed to be used on specific microphones and they should
be used only on these microphones. Otherwise, errors may result or micro-
phones may be permanently damaged.
In use, the sound level generated by the calibrator should correspond
to the SLM reading. If it does not, the instrument instruction book' must
be consulted to determine how adjustments are to be made. All calibrations
should be made using the Flat- or C-weighting settings on the SLM unless
otherwise specified by the manufacturer. As a secondary check on the per-
formance of the A-weighting, the difference in levels between SLM reading
and the calibrator level may be compared with the specified A-weighted
relative response at each test frequency (see Figure 11.2).
Caution should be exercised when using calibrators at atmospheric
pressures different from that at sea level. Normally, correction data are
supplied by the instrument manufacturers.
11.2 Field Measurements
Systematic procedures must be followed to prepare for sound pressure
level measurements. These steps may be conveniently divided between those
taken before leaving for the measurement site and those taken after reaching
the site.
A. Before leaving for the measurement site:
1. Determine the purpose of the measurements and obtain a
complete description of the measurement sites and noise
sources.
2. Assemble the necessary equipment and supplies:
a) SLM
b) calibrator
c) windscreen
d) tripod
e) cables
f) batteries
g) data forms
Z?
-------
h) pens and pencils
i) auxiliary apparatus (e.g., anemometer, measuring
tape, compass, thermometer, timer, analysis
equipment, etc.)
3. Check batteries and replace if necessary
4. Calibrate all equipment.
B. At each measurement site:
1. Record wind speed and temperature. Do not attempt
measurements:
a) if wind speed is greater than 20 km/hr (12 mph)
b) if temperature is outside range recommended by
the SLM manufacturer
c) during periods of precipitation.
2. Select the measurement positions.
a) make a sketch of the site and describe the location
of the SLM positions accurately.
b) determine distances to sources and describe ground
conditions and possible barriers or reflectors on
or near the path from the measurement point to
each source.
c) mount the SLM or microphone on a tripod if measure-
ments cover an extended period of time.
3. Check batteries and replace if necessary
4. Check calibration of equipment and adjust if necessary.
Make a note of all calibrations and adjustments in ink
on the data form.
5. Select the frequency weighting network and adjust the
SLM attenuator (level adjustment) until the meter
reads on-scale (preferably to the riqht side of the
meter where dB indications are widely spaced).
6. Follow the SLM manufacturer's directions in operating
the instrument and in positioning the microphone. Use
a clean recommended windscreen for all outdoor measurements.
7. Record all measurement data and source descriptions in ink.
8. Check calibration of SLM when measurements have been
completed at each site.
11.3 Manual Sampling Procedures
11.3.1 Determination of Statistical Distribution of Noise Levels (Ln)
A statistical distribution of noise levels uses sound pressure level
measurements taken at predetermined time intervals over some specified
observation period. From these data the percentage of time that any
specified sound level is exceeded can be determined. Alternately, the
-------
sound level that is exceeded a specified percentage of the observation time
such as L"iq, L50. and Lgo, which are the percentile levels-exceeded 10, 50,
and 90 percent of the observation time, can be determined. The most common
percentile level used to describe community sounds is the Lio The L50 is
generally taken as the mean level while Lgo is taken as the ambient
(background) level.
The length of the observation period must be adequate to describe the
variation in sound level. A rule-of-thumb for determining the required
period of observation is that the time period should be long enough to
accumulate at least a number of samples equal to 10 times the total sound
level fluctuation. For example, if the sound levels fluctuate over a range
of 14 dB (ฑ 7 dB), the total number of samples should be in excess of 140.
The total time in which the samples are taken depends upon the interval
between samples and the sample time. From previous studies (6,7,8) it has
been determined that a sampling rate of once every ten seconds yields a
95 percent confidence limit.3 In other words, the Lio value will be within
ฑ 3 dB of the correct value for this sampling rate. For the example given
above, the total observation time necessary to take 140 samples will be
about 23 minutes.
Equipment: The basic equipment required for manual sampling is a
sound level meter, a timing device, and a data sheet (see Figure 11.5).
The timing device may be a watch with a second hand, or an automatic timer
with an audible or visual indicator that can be set to various time intervals.
A small tape recorder also may be desirable to use to describe source
and measurement conditions (not for recording the sound being measured).
Care should be taken to prevent verbal communications between the operator
and the recorder from being picked up by the SIM microphone during
measurements.
Procedure: The procedure for determining the statistical distribution
and the corresponding Lio and Lgo value is as follows:
1) Check the battery of the SLM and other battery operated equipment
2) Check the calibration of the SLM according to the instrument
manufacturer's instructions (also see Section 11.1.4)
3) Consult the SLM manufacturer's instructions and Section 11.1.3
to determine proper operating procedures.
4) Locate the SLM microphone at the point of interest
5) Set the SLM weighting switch to the "A" position and the
meter response switch to the "Fast" position.
6) Turn the SLM ON and observe the range of the meter fluctua-
tions. Multiply this range by 10 to compute the total
number of samples required. (If this range increases
during the course of taking data, the number of samples
required will also increase; however, the number of samples
required is not changed if the fluctuation range decreases.)
3The mathematically correct procedure for determining the error associated
with a sampling method is to have the sample spaced randomly in time.
However, this is inconvenient for field measurements. An equally correct
error analysis can be performed if the samples are regularly spaced, but
the signal varies randomly in time. This is the approach taken here.
2^
-------
Sound Level Meter T vpeC ฃ 1AL
Starting Tihe-? '>("> ah ph
Sampling Intfrvai (o "ieo-dc
Total Observation Time^ฆ*-"ปTe*
oqt gc
Primary Noise Source
Secondary Noise Source Trvth-.
Comments
Q*1
-UC.zzsJ^l.
R
V
>
o
J
3
o
'r.
"3
v
9
e
U:7
r
. 4
: 3
C'2
ฆ' I
H
~ B
7
6
1 5
4
3
1
a
4
ฆJ
I
<
1
0
c
8
7
6
5
4
3
2
1
C
9
8
_ 7
i 6
5
4
3
2
I
CO
z
TT
i
is ts ~ ~
y s \
t' is tsilSX
t/if " i
vv y yy
Is f Is i^is
t/ is isf.
v V f IS i/
k yy
VSV \AV
v'r ry\ v
v Vy J?
V) K! v~ f1 f
y V : v> (/> j/
vyy y.ฅ
f i/ fj/i/'
^ is'is
r * V>V
1/ K ^Vi i.
L_L
1 I
rr
i I
Xl
-L-L
4-L
1 I
vT~\-
t/ Wis ls\\/
trl/v'
iA /_ r vw
y'y
y' / y yy
^y.y^y
'jjfViHt:
iny; Av
V\y
r'.s
V V "
t/j"yy*Y
V' ' i
i
IQ-
~
V
v
v v
7
I
35
I 2 3
Column 1: Number of observations
at each level.
Column 2: Cumulative total number
of observations.
Column 3: Percentiles for each
sound level.
.2.d^L __LLl lLad. 1 J_ J_Li.
Number ol Occurences
40 I.X.
ฑ_
X
2 '
ฆi
H
2
nr
u
/0
g;
fc-
to
1 (e
t~t>
30
/6
f%
22
ZR
'A
/I
6
G
c.
!*-
/ ^
!&
20
?fc
3a
?0L
(.o
lb
12
!2i_
'3g
/Sb
iy%
til
2 28
23i
2V-1
0-
a
3
7
7"
"8"
//_
21
3!
3?
fr
ซ2
ฃf"
fv-
.Lซf
Q,
t
-f
o -< z
i- ฆ
-< o sป
-n |
o
2 ^ CO
m J>
\1 1,1 -1
N 7^ -T3
1 "
D
1
u
?
1
\3
Figure 11.5 Completed Manual Sampling Data Sheet
-------
7) Every 10 seconds read the instantaneous A-weighted sound
level and record this level as an occurrence by making a
check in the appropriate row of the data sheet (see Figure
11.5). Work from left to right within each row as sample
levels re-occur.
8) After the appropriate number of samples has been taken, add
the number of check marks in each row and record this number
in column one of the data sheet (see Figure 11.5).
9) Add the row totals in column one beginning with the highest
sound pressure level total (top figures) and record these
numbers in column two (i.e., from the top of column 2,
4=4, 4+2=6, 4+2+2=8, etc.)
10) Divide each number in column two by the total number of
occurrences (bottom number in column 2) and multiply by
100 (i.e., (4r242)xl00, (6^242)xl00, etc.). Enter these
numbers in column three.
The numbers in column 3 are percentiles for each sound level that
correspond with the percentage of time that the sound level was exceeded.
In the work sheet example, 80 dB was exceeded 7 percent of the time and
78.5 dB was exceeded 10 percent of the time (i.e., L-jq=78.5 dB, 150=70.0 dB,
Lg0=64.8 dB. These percentile determinations are accurate within ฑ3 dB.
11.3.2 Determination of the Energy Equivalent Continuous Level (Leg)
An energy equivalent continuous level, Leq, is another effective means
for describing sounds with fluctuating levels. The Environmental Protection
Agency considers this A-weighted energy equivalent sound level, Leq> and the
24-hour day/night energy equivalent level, Lnn, to be the best measures of
environmental noise as it relates to public nealth and welfare (9). The
Leq descriptor accounts for both duration and level of all sounds during the
measurement period. Because Leg is related to energy, it provides weighting
toward the occasional high-level events such as the passing by of trucks,
motorcycles, and aircraft. The Leq also affords a reasonably good measure
of intrusiveness. The advantage of using Leq may be summarized as follows:
1) It is responsive to the effects of high amplitude
events that can contribute significantly to the
intrusiveness and unacceptability of noise;
2) Because it is energy-based, the effects of adding
or subtracting sources can be handled relatively
easily and directly;
3) Because of (2), predictions required by environ-
mental impact statements can be made with much greater
certainty than with maximum or statistical level
descriptors which cannot be combined with certainty
by any simple means to yield predicted values.
3 7
-------
The following simple example of an Leq calculation is helpful in
understanding the Leq descriptor. Assume that the A-weighted sound pressure
levels measured over three equal time periods are 20, 40, and 60 dB respec-
tively. The average intensity (energy per unit time per unit area) at the
location where the sound pressure levels were measured is calculated by:
Lfl - 20 dB * 20 log10 -jj
and P = 10
Pref
where p is the sound pressure at that location and pref is 20- yPa
(0.00002 N/m2).
In the same manner -2 = 100 and 1000 for 40 and 60 dB respectively.
Pref
Then, for 3 20 dB:
Pi * 10 x .00002 = .0002 N/m2
and I] = p]2/pc 3 .00000004/pc watts/m2
where I-[ is the sound intensity for sound pressure pi,
and pc is a constant (called the impedance) characteristic of air.
For La = 40 dB: p2 =100 x .00002 3 .002 N/m?
and 12 3 P2^/pc 3 .000004/pc watts/m2
For Lp = 60 dB: p3 3 1000 x .00002 = .02 N/m2
and I3 3 P32/pc 3 ,0004/pc watts/m2
Now .the average intensity is
_ Il+I2+I1 _ .0004 + .000004 + .00000004
avg * 3 " 3pc
3 .00040404 3 .000135/pc watts/m2,
3pc
and the sound pressure equivalent for this average intensity is:
p = /l^~pc 3 .000135/pc) x pc = .0116 N/m2
Then p 3 .0116 3 580
P^ef .00002
and Leq 3 20 log 580 = 55 dB.
3Z
-------
The SLM may be used to approximate Leq by using fast response measurements
made periodically. If sample levels are denoted by Lj and the total number
of samples by N, then
as follows:
Leq a l50 + 0-07(Lio-L5o)2.
For example, if L50 = 70.0 dB and l_io = 78.5 dB, as in the example shown in
11.3, then
Leq = 70 + 0.07 (78.5-70)2 = 75.1 dB.
Obviously, measurements of Leq must have the same general guidelines for
the length of measurement times as those described above for Lio and L50.
Shortcuts can be taken if the source operates with highly repeatable periodic
cycles, as with trash compactors or domestic air conditioners. Also, short
term measurements may be justified in situations where it is only necessary
to determine that a prescribed Leq level has been exceeded. Table 11.1 shows
the equivalent Leq for time durations of one hour or less. If the levels in
the table persist longer than the measurement times shown, then the one-hour
Leq value heading the columns will be exceeded, even if the source is quiet
for the remainder of the hour.
The most straightforward method for determining Lpq is, of course, to
measure it directly. Unfortunately, instruments for this purpose are
expensive and they are not widely used at this time.
11.3.3 Determining Day-Night Level (Ldn)
The L Ln, and Ldn can be determined
conveniently from the graph in Figure 11.6. For example if Ld * 65 dB and
Ln = 57 dB then Ln-Ld = -8 dB. This Ln-Ld value corresponds to an Ldn-l-d
= 1 dB, so Ldn = 65 + 1 = 66 dB.
Leq 3 10 109 C(210Ll/10)/N].
may b
d L-jn values
The formula is
33
-------
Table 11.1
Short Time Determination of Leq
If levels shown persist for longer than the time shown, the one-hour Leq
will be exceeded, even if the source was quiet for remainder of the hour.
Measurement
(minutes) Equivalent Leg Values
60
45 dB
50 dB
55 dB
60 dB
65 dB
70 dB
75 dB
30
48
53
58
63
68
73
78
15
51
56
61
66
71
76
81
8
54
59
64
69
74
79
84
4
57
62
67
72
77
82
87
2
60
65
70
75
80
85
90
1
63
68
73
78
83
88
93
0.5
66
71
76
81
86
91
96
0.25
69
74
79
84
89
94
99
24
-------
00
-------
NOISE LEVEL DATA
Day of week Month
Location
Day Y ear
Measurements made by
Weather:
Temperature
Humidity
Wind
F Cold
% Dry
mph. Calm
Sound sources in area
Cool
Humid
Moderate
Rain.*
Hot
Snow*
Breezy Gusty
Strong'*
Sound level meter Type
Calibrator Type
Battery check Time:
hrs
Sound level meter
Calibrator
Calibration of Sound level meter
1000Hz
Notes:
dB
hrs
dB
Serial No.
Serial No.
hrs
dB
hrs
dB
* Measurements not recommended in unusual weather conditions.
36
-------
NOISE LEVEL DATA
Sketch of area.
Day oฃ week_ Month Day Year
Location
Show buildings, trees, bushes, parked vehicles, distances to sound
sources. Mark location of microphone withฎ. Show microphone height.
-------
NOISE LEVEL DATA
Sound pressure level measurements
Day of week ' Month Day-
Location
Y ear
/
/
-$o
r -
f s.& Vv
V*
-------
NOISE SURVEY DATA
DATE
LOCATION
OCTAVE BAND
(Center Freq. )
DECIBELS
DECIBELS
DECIBELS
DECIBELS
DECIBELS
DECIBELS
Sound Measuring
Equipment
Type
Model H
Serial H
Type
Model H
Serial H
OCTAVE BAND
(Cente r F req. )
Over all-Linear
Overall-Linear
A-Frequency
Weighting
A -Frequency
Weighting
31 Hz
31 Hz
62 Hz
62 Hz
D
125 Hz
125 Hz
250 Hz
250 Hz
500 Hz
1000 Hz
2000 Hz
500 Hz
1000 Hz
2000 Hz
4000 Hz
4000 Hz
8000 Hz
Indicate
Fast or Slow
Response
Taken By:
Time:
Remarks:
Time:
Time:
Remarks:
Remarks:
Time:
Remarks:
Time:
Time:.
Remarks:
Rema rks:
8000 Hz
FIELD
CALIBRATION
Cal. Type
Time
Hz. d B
125.
250.
500.
1000.
2000.
-------
o
Sound Level Meter Type
Starting Time ah, ph
Sampling Interval
Serial
Primary Noise Source
Secondary Noise Source.
Comments
Total Observation Time.
I 2 3
tu
a
3
o
cn
x>
J9
r a
6
B
1 1 !
-
-
-
-
-
-
-
-
-
...
-
-
-
-
-
-
-
-
-
-
-
-
-
-
--
-
I '5
' A
1- -4
13
0
"9
_ fi
L7
6
5
ฆA
: 2
1
0
Q
. 8
si
' 4
. 1. ; !.
i i !
-
-
-
-
-
-
-
-
-
-
--
-
-
-
-
-
-
-
-
-
-
-
w
-
-
--
-
-
-
-
-
-
-
-
-
i i_ _ |.
4_ i_ _
i 1-
[J.
-
-
-
--
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
"
-
-
-
-
-
_
-
-
-
-
-
-
-
-
-
-
-
-
i
i i ซ
i
i
-
1
-
-
-
-
:
_
-
-
-
-
-
-
-
-
-
-
-
-
-
-
:
-
-
-
-
-
;
:
-
1.:.
1
i
4
-i-
1
-
-
~
-
-
__
1
-
-
-
-
-
-
-
-
-
-
-
-
-
~
-
-
-
---
i-L
' ; i
i . t--f
i
=
-
-
-
-
-
-
-
-
. 1 i
1
L
i
-
-
-
-
-
-
-
:
:
-
-
-
ฆ-
-
-
-
~
3
2
1
0
9
8
\7
-
-
ฆ -
-
--
-
-
-
-
-
-
-
-
-
-
-
-
-
i
-
-
___
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
f
-
E
-
-
-
-
-
-
-
-
6
5
i
.. r -
i
-
-
-
_
4
ป
t
~L
i
-
-
-
-
-
-
-
-
-
-
-
~
1 i
h
i o
'1
-
-
-
-
~
-
-
-
i i
-
-
-
-
-
-
J-
i
-
-
-
--
-
I(
<
IC
if
sc
Number of Occurences
-------
TRANSPORTATION NOISE PREDICTION TECHNIQUES
Highway Noise-
FH5>ffi.-RD-77-103. FHWA Highway Traffic Noise Prediction Model. Available from: U. S,
DOT, FHW\, Office of Research/Environmental Policy, Washington, D. C. 20590; or
from National Technical Information Service (NTIS), U. S. Dept. of Commerce, 5235
Port Royal Rd., Springfield, VA 22161.
FHWA Technical Advisory T 50*40.5, Change 1. "Hand-held Calculator Listings for the
FHฎ. Highway Traffic Noise Prediction Model". Available as above.
"Estimation of Community Noise Exposure in Terms of Day-Night Average Level Noise
Contours" (draft) J. W. Swing. Available from: California State Office of Noise
Control, 2151 Berkeley Way, Berkeley, CA 9^70U.
Railroad Noise-
Assessment of Noise Environments Around Railroad Operations, J. W. Swing and
D. B. Pies, Wyle Laboratories Report WCR 73-5. Available from Wyle Research,
12S Maryland Street, El Segundo, CA.
"Estimation of Community Noise Exposure in Terms of Day-Night Average Level Noise
Contours" (See Highway Noise, above).
Airport Noise-
Developing Noise Exposure Contours for General Aviation Airports, Dwight E. Bishop,
et al. Bolt, Beranek and Newman, 1975. Report No. FAA-AS-75-1. Available from
NTIS (See above), No. AD/A-023 ^29-
4 7
-------
FIGURE A-1
SOUND LEVEL EVALUATION FORM
CHECK ONE: ( ) Ambient Sound Level Evaluation ( ) Alleged Ollenslve Sound Level Evaluation
Requested by: Address: _ Phone:
Regarding: Address: Piซnซ .
Sound Source:
Equipment Used:
Microphone Location
Weather: Time Started: Time Finished: Sample Interval:
Land Use Designation: Community Classification: Median Ambient Sound Level: (dBA)
Min > Median. Mln. > +5 dBA: M*> > + 10 dBA: Min > + 15 dBA: Min > + 20dBA: ___
30
35
C: Cm
1, TiซkIi
hk Uototetetm
A IMrirt En****
40
45
60 55 60
Oaclhata "*" WtelghlMl NMvxnk -Ite 20<| H**>
65
70
75
80
A: Afccrซ4
H: IMteopta*
00#Mf
Jt'AnAlenl/er / OWwielr* Sewd l#vel
Conduclad By._
l>at* o4 Study: _
-------
(/O *
ฃ
*
li
I
/
FIGUUG A-1
SOUND LEVEL EVALUATION FOIttl
Ofc.iZK trf*. (p^ii *P/TK - Jff. ...
84M
V4y *V *(*trn+r 1li dOA
Mซ > iSOdiiA:
t*
It!
lu
;
:
;
VI
...
-
-ฆ
-
-
_
-
-
-
-
..
--
-
-
...
_.
---
_ _
-
...
.
_
-
-
-
...
-
....
-
-
-
~
-
-
-
-
-
-
-
-
....
-
-
_
-
-
-
-
c
c
.
c
T
<
.
_
J
-ฆ
_
___
-
-
__
-
T
iU^riw
41)
4t>
U) l*tj U)
Hrfป "A ' Vteiylitea Ilu4*ซ*k IW :1I ซj IliM
CmwJw.MI iiy
It)
/u
t.ii
A AmuiiII
M IUh.(4
lit*17 7
-------
REFERENCES:
Environmental Noise Pollution, Patrick F. Cunniff, John Wiley &
Sons, New York, 1977.
Guidelines for Considering Noise in Land Use Planning and Control,
Federal Interagency Committee on Urban Noise, June 1980.
Guidelines for the Preparation and Content of Noise Elements of
the General Plan, California Office of Noise Control, February 1976.
Highway Noise: A Reprint of the Audible Landscape: A Manual for
Highway Noise and Land Use, U.S. Dept. of Transportation, FHWA,
August 19 76.
Noise: A Health Problem, EPA, August 19 78.
Our Acoustic Environment, Frederick A. White, A Wiley-Interscience
Publication, John Wiley & Sons, New York 1975.
Protective Noise Levels, EPA 550/9-79-100, Novermber 1978.
Quiet Communities: I and II, National Association of Counties
Research, Inc., 1979 and 1980.
44
------- |