Acoustical and social data on community reactions to aircraft nois

Connor, W. K.

English

NASA Technical Reports Server

40. COMMUNITY REACTIONS TO AIRCRAFT NOISE 
NOISE MEASUREMENTS 
By William K. Connor 
TRACOR, Inc. 
SUMMARY 
Aircraft noise measurements were made in communities exposed in varying degrees 
to the noise of flight operations from major airports. The primary purpose of these 
measurements was to define the noise exposure for a 3-month period in areas  for which 
social data were also obtained by means of interviews. The acoustical and social data 
are being used in a study of community reaction to aircraft noise. Further data must be 
taken before an extensive analysis is performed. A secondary purpose of the noise mea- 
surement program was to evaluate, in a community context, noise level estimates obtained 
from the guide "Land Use Planning With Respect to Aircraft Noise." A comparison of 
measured noise levels with the estimates revealed no inconsistencies in 85 percent of the 
cases examined, and the discrepancy was in no case greater than 10 PNdB. The noise 
data also afforded a comparison of several acoustical parameters which are used as mea- 
sures of aircraft noise. For such community data, there was a standard deviation of 
3 units or less between any two parameters, except for certain pairs including speech 
interference level. 
INTRODUCTION 
This paper and reference 1 describe a current program of research concerning 
community reaction to aircraft noise (under Contract NASw-1549). Although procedures 
for computing psychophysical parameters of aircraft noise a r e  well developed (ref. 2), 
there as yet exists no methodology capable of accurately predicting the reaction of indi- 
viduals or groups to a given noise exposure. Annoyance resulting from aircraft noise has 
been known to vary from one person or  community to another under identical exposure 
conditions. The social and psychological factors which may account for such variations 
are the central focus of this study. 
The paper at hand deals with the aircraft noise exposure data related to this study. 
The social data and analysis a r e  discussed in the coordinate paper by Hazard (ref. 1). 
https://ntrs.nasa.gov/search.jsp?R=19690002249 2020-03-12T06:02:48+00:00Z
DISCUSSION 
Survey Program 
The plan of research requires that both social and acoustical data be taken around 
several major commercial airports located in cities of the United States. The areas in 
which such data were acquired were confined to within a 12-mile radius of the airport i n  
question. A further delineation of survey areas was made by using a sampling plan which 
selected a balanced cross section of the population from the standpoint of socioeconomic 
and noise exposure variables. 
The actual sample ultimately consisted of from 11 to 22 census tracts in  each city. 
Many of these census tracts were situated more or less on a line extended from the ends 
of principal runways. The noise exposure in such tracts tended to be due-largely to air- 
craft flyovers associated with the particular runway. In other sample areas located 
within 3 miles of the airport, noise exposure was due to a combination of flyovers, other 
flight operations, and ground operations. The sample tracts were surveyed by both social 
and acoustical scientists, but not necessarily at the same time. 
The program is comprised of two active phases of approximately 1 year each. In 
the first phase, four cities were surveyed in the summer of 1967. In the second phase, 
not yet begun, data will be obtained in three more cities. Only a preliminary analysis 
has been made of the data now available. A comprehensive analysis culminating in major 
conclusions can be performed only after the survey data from all seven cities are 
available. 
Exposure to Aircraft Noise 
Requirements for acoustical data. - The primary function of the acoustical measure- 
ments is to define the aircraft noise exposure for each of the sample areas for a period 
of at least 3 months immediately prior to the social survey. This minimum period was 
agreed upon in consultation with other scientists active in the general field of human 
reaction to noise. It was also agreed that the best formulation of long-term aircraft 
noise exposure was in te rms of PNdB with corrections for discrete frequency components, 
This formulation requires that the acoustical data be analyzed by using bands no wider 
than 1/3 octave and that the noise be sampled at least once per second in real time. A 
secondary purpose of the field measurements is to obtain some validation of the aircraft 
noise level contours in the guide "Land Use Planning With Respect to Aircraft Noise" 
(ref. 3), hereinafter referred to as "Land Use  Planning." The fundamental question to be 
answered is, 'lHow do noise levels predicted on the basis of the guide compare with levels 
measured in  various communities ?l' Obviously, the usefulness of the guide is contingent 
upon the answer to this question. 
6 50 
Data acquisition.- The acoustical data requirements entailed tape recording of air- 
craft noise at the various survey sample areas in  each city. The recording systems 
incorporated automatic electrical calibration after each noise recording and a 48-interval 
time-of-day encoded signal. Both calibration and time signals were recorded on the data 
tapes. The recording site, apparent aircraft operations (when visible), and general 
observations were logged and keyed to the data tape reels. An additional feature of the 
recording systems was an automatic monitor and control unit whereby recording was 
initiated when the A-weighted sound pressure level (SPL) exceeded a preset value. A 
member of the measurement team was in  attendance at all times, however. 
Data processing. - The large amount of recorded acoustical data necessitated auto- 
matic analysis. An analog/digital system built for this purpose is shown in block-diagram 
form in figure 1. The system output, in digital tape form, consists of SPL's in each of 
twenty-four 1/3-octave bands (as well as A-weighted (ref. 4) and N-weighted (ref: 5) 
SPL's) for each second of analog data tape, together with appropriate identification and 
index markers. These data were further processed with a series of routines on the 
UNIVAC 1108 computer to produce a second set of digital tapes which contained the values 
of a number of psychophysical parameters (perceived noise levels in PNdB (refs. 6 and 7), 
with and without corrections for discrete frequency components; loudness level in phons 
(ref. 8); speech interference levels; etc.), again for 1-second sampling intervals. These 
tapes also included values of peak levels, durations of various parameters above given 
thresholds, and other pertinent information. 
Determination of noise exposure.- It was impossible for several reasons to sample 
aircraft noise continuously in each survey tract over the entire 3-month period of interest. 
Therefore, the procedure shown in block form in figure 2 was used in the process of com- 
puting long-term noise exposure. Noise data were taken in  as many tracts as possible 
under known airport operating conditions. These conditions included the type of operation 
of heavy aircraft (landing or take-off) as well as the runway usage during each noise- 
recording period. 
Hourly wind data for the 3 months of interest, together with information from the 
airport control-tower staff concerning local runway-assignment practices as related to 
wind conditions, were processed with a simple computer routine to determine runway 
usage over the 3-month period. This usage factor was multiplied by the airport opera- 
tions count (a function of time of day) to obtain the number and type of heavy-aircraft 
operations utilizing each runway according to time of day, averaged over the 3-month 
period. An additional weighting factor related to flight path made it possible to obtain 
the average number of operations passing over or  near each sample tract. 
651 
The average number of operations and the maximum PNL occurring during each 
particular type of operation were combined into the following noise exposure index for 
use in the preliminary analysis of the combined social and acoustical data: 
Exposure index = PNL + A loglo(Nday + BNfight) 
where 
PNL maximum measured flyover perceived noise level, energy-averaged for all 
observed flyovers of a particular type 
*day 7 Nnight number of daytime, nighttime flyovers of the particular type 
A,B constants 
This index is a general case of the composite noise rating (CNR) formulation (ref. 3), 
which has had considerable use. A value (or set of values) was assigned to each sample 
tract which was surveyed in the field study. (In actuality, one further step was involved 
in determining the noise exposure values: The indices for all aircraft operation types 
affecting each tract were combined on an  energy-addition basis.) 
For some tracts, noise data could not be obtained in the field for all operating 
conditions. However, it was  usually possible in these cases to use data taken at a site 
symmetrically opposite the airport. These data were applicable to the subject tract when 
the direction of aircraft operations was reversed. If no field noise data whatsoever could 
be obtained, noise contours for the most prevalent aircraft types taken from "Land U s e  
Planning" were used to estimate maximum flyover levels. 
Results of Preliminary Analysis 
Aircraft operations data.- A plot of the aircraft operations count as a function of 
time of day for each of the four airports studied thus far is shown in figure 3. Although 
the airports varied considerably in size, the daily pattern of operations was remarkably 
uniform from one to another. This pattern may be partially attributed to public travel 
requirements. It is also noteworthy that nighttime operations, which are known to pro- 
duce considerable annoyance and complaints, represent only a small fraction of the total 
number. 
Noise level data.- The aircraft noise recorded at the various survey sites, after 
the processing described previously, was analyzed to find the maximum PNL value for 
each flyover. The results were plotted for each of 73 original data tape reels in the form 
of a distribution. Two such distributions a r e  shown in figures 4 and 5. Each distribu- 
tion applies to a single survey site and usually to a particular known mode of operation of 
6 52 
the airport. Corrections for discrete frequency noise components were not included in 
these PNL values, in order to make possible a direct comparison with the uncorrected 
PNL's of the "Land Use Planning" contours. The energy averages of these distributions 
were used in computing the noise exposure indices for the various survey tracts according 
to the formula given in a foregoing section. 
An interesting aspect of the PNL distributions is the variation in their shape from 
one survey tract to another. In some (fig. 4), there is a highly peaked distribution, which 
indicates a predominance of aircraft noise from a single type of operation (and aircraft). 
In others (fig. 5), there is a quite broad distribution, which perhaps indicates contribu- 
tions from aircraft operations on more than one runway as well as variations in aircraft, 
flight procedure, trajectory, and so forth. The procedure of energy averaging, although 
consistent with accepted practice, places the greatest emphasis upon the highest observed 
PNL values in these distributions. In consequence, essentially no effect is attributed to 
flyover noise much below the highest level. It would seem that a number of flyovers with 
maximums of 90 PNdB are significant in terms of human annoyance even i f  an equal num- 
ber attained 100 PNdB. Therefore, further analysis of the data will include formulations 
for correlation with annoyance measures derived from the social data which give greater 
weight to the less noisy flyovers above a certain threshold level. 
For each of the PNL distributions, estimates of the noise maximums were made by 
using the "Land U s e  Planning" contours for civil aircraft ranging from four-engine piston 
and turboprop aircraft to four-engine jet aircraft. These estimates were based upon the 
operations proximal to the recording site under the prevailing wind conditions. The range 
of these estimates is shown .above the plots of figures 4 and 5 for comparison. A positive 
indication of inconsistency between the predicted and the measured levels is for the latter 
to exceed the former significantly. (The reverse situation may mean only that the noisier 
aircraft or  operations are not represented.) Such an indication was present in 11 of the 
73 distributions. The maximum difference between the highest predicted and the highest 
measured levels was 10 PNdB. It may be concluded that the "Land Use  Planning" con- 
tours afford a reasonably good estimate of aircraft noise levels provided that vagaries of 
local operation a re  known and taken into account. 
Comparison of noise parameters. - The format of the analyzed, computer-processed 
acoustical data made possible a ready comparison of several noise parameters associated 
with effects on humans. Similar comparisons have been made (refs. 9, 10, and ll), but 
not for  so large a mass of data (about 4730 flyovers) o r  for acoustical data so well- 
distributed over a wide range of community exposure conditions. Some of the parameters 
to be compared herein are defined for the present purpose as follows: 
6 53 
PNdBl 
PNdB2 
PNdB3 
PHONS 
dBN 
dBA 
SIL 
maximum flyover PNdB value computed (with pure tone corrections) from 
1/3-octave band data sampled once per second 
PNdBl without pure tone corrections 
PNdB value computed (without pure tone corrections) from maximum flyover 
levels occurring in each 1/3-octave band (not necessarily simultaneously), 
sampled once per second (ref. 12) 
maximum flyover value of loudness level computed according to Stevens' 
Mark VI method (ref. 8) 
maximum flyover SPL weighted according to inverse of 40-noy contour 
(ref. 5); zero reference at 1 kHz 
maximum flyover A-weighted SPL (ref. 4) 
maximum flyover speech interference level (arithmetic average of SPL's 
in the 1-kHz, 2-kHz, and 4-kHz octave bands) 
The numerical differences between the values of every pair of these parameters were 
analyzed for approximately 4730 recorded flyovers. The results are shown in matrix 
form in the following table: 
PNdBl 
PNdB2 
PNdB3 
PHONS 
dBN 
dBA 
Average for all flyovers of (value in left-hand column minus value of row param- * 
e te r ) / s  t andar d deviation. 
The usefulness of each noise measure as applied to community-wide aircraft noise 
is apparent from the data of the table. It can be seen that the three PNdB-type measures 
correlate with one another quite well; the spread is no larger than that normally encoun- 
tered in the data of psychophysical comparisons of such noise. The various measures in 
6 54 
the table are in order of descending correlation with PNdB1, the most recent and sophis- 
ticated form. The two weighted-SPL measures, with standard deviations with respect to 
PNdBl of 2.6 and 3.0 units, should certainly be adequate for most aircraft noise measure- 
ments. PNdBl should be used for limited classes of data and for aircraft-certification 
purposes, however. The SIL's can hardly be expected to correlate well with perceived 
noise levels, but it is also of interest to see i f  they can be approximated by dBA or dBN. 
Unfortunately, a reasonable approximation cannot be made, although this does not neces- 
sarily mean that dBA is not a useful speech interference measure itself. Indeed it has 
been shown that, for some types of noise at least, dBA is fully as good a measure as the 
SIL as computed for the present comparison. (See ref. 13.) 
CONCLUDING REMARKS 
In the first phase of this study, now complete, a large mass of acoustical data was 
acquired. These data were used to derive a noise exposure index for the preliminary 
analysis of the social data and also for secondary evaluations. Following the anticipated 
second phase of the study, the complete acoustical data will be further analyzed to test 
the relative power of several different formulations of noise exposure in predicting com- 
munity reaction. 
6 55 
REFERENCES 
1. Hazard, William R.: Community Reactions to Aircraft Noise - Public Reactions. 
Conference on Progress of NASA Research Relating to Noise Alleviation of Large 
Subsonic Je t  Aircraft, NASA SP-189, 1968. (Paper No. 41 herein.) 
2. Kryter, K. D.: Concepts of Perceived Noisiness, Their Implementation and Applica- 
tion. J. Acoust. SOC. Amer., vol. 43, no. 2, Feb. 1968, pp. 344-361. 
3. Anon.: Land U s e  Planning With Respect to Aircraft Noise. AFM 86-5, TM 5-365, 
NAVDOCKS P-98, U.S. Dep. Defense, Oct. 1, 1964. (Available from DDC as 
AD 615015.) 
4. Anon.: American Standard Specification for General-Purpose Sound Level Meters. 
S1.4-1961, Amer. Stand. Ass., Inc., Jan. 9, 1961. 
5. Kryter, K, D.; and Pearsons, K. S.: Modification of Noy Tables. J. Acoust. SOC. 
Amer. (Lett. to Ed.), vol. 36, no. 2, Feb. 1964, pp. 394-397. 
6. Kryter, Karl D.: Scaling Human Reactions to the Sound From Aircraft. J. Acoust. 
SOC. Amer., vol. 31, no. 11, Nov. 1959, pp. 1415-1429. 
7. Kryter, Karl D; and Pearsons, Karl S.: Some Effects of Spectral Content and Dura- 
tion on Perceived Noise Level. J. Acoust. SOC. Amer., vol. 35, no. 6, June 1963, 
pp. 866-883. 
8. Stevens, S. S.: Procedure for Calculating Loudness: Mark VI. J. Acoust. SOC. 
Amer., vol. 33, no. 11, Nov. 1961, pp. 1577-1585. 
9. Bishop, Dwight E.: Descriptions of Flyover Noise Signals Produced by Various Jet 
Transport Aircraft. Tech. Rep. DS-67-18, FAA, Aug. 1967. 
10. Robinson, D. W.; Bowsher, J. M.; and Copeland, W. C.: On Judging the Noise From 
Aircraft in Flight. Acustica, vol. 13, no. 5, 1963, pp. 324-336. 
11. Bishop, Dwight E.: Frequency Spectrum and Time Duration Descriptions of Aircraft 
Flyover Noise Signals. Tech. Rep. DS-67-6, FAA, May 1967. 
12. Anon.: Procedure for Describing Aircraft Noise Around an Airport. Recommenda- 
tion R 507, 1st ed., Int. Organ. Stand., Oct. 1966. 
13. Klumpp, R. G.; and Webster, J. C.: Physical Measurements of Equally Speech- 
Interfering Navy Noises. J. Acoust. SOC. Amer., vol. 35, no. 9, Sept. 1963, 
pp. 1328-1338. 
6 56 
BLOCK DIAGRAM OF ACOUSTICAL DATA-PROCESSING SYSTEM 
I I  
u z 
Y 
J 
P 
z 
u . rr 
Y w
5: 
113-OCTAVE BAND 
F I L T E R S  
I 
LINEAR-TO-LOG 
CONVERTER ~ 
MONITOR 
OSCILLOSCOPE 
CONVERTER 
LINEAR DETECTORS/ 
MULTIPLEXER 
CONTROL 
U N I T  
- 
- 
Figure 1 
PROCEDURE FOR COMPUTING HOURLY NOISE EXPOSURE IN A GIVEN SURVEY TRACT Fl /:Yp111 MEASURE0 FLYOVER 
RUNWAY 
USAGE 
FLIGHT-PATH 
VAR I AT IONS 
FLYOVERS 0 
~ 
NOISE EXPOSURE 
Figure 2 
6 57 
30 
v) 
(3 
Q: 
0 
z a 
8 20 
a 
!z 
0 
LL 
LL 
0 
3 IO 
5! 
0 
6 58 
HEAVY-AIRCRAFT OPERATIONS AS A FUNCTION OF TIME 
OF DAY FOR FOUR AIRPORTS 
300 
g 250 
2 200 
2 
a a 
I- 
0 
u. 
0 
6 150 
2 
m 
z 
100 
50 
:n CITY A 
01 I I I I I I I I 
M 3 6 9 N 3 6 9 M  
TIME OF OAY 
Figure 3 
DISTRIBUTION OF MEASURED PN L'S - S ITE  A 
RANGE OF ESTIMATES FROM 
"LAND USE PLANNING" 
TOTAL NO.= 89 1 
I I t 
100 110 120 
MAXIMUM PERCEIVED NOISE LEVEL, PNdB 
Figure 4 
J 
DISTRIBUTION OF MEASURED PNL 'S- S ITE  B 
RANGE OF ESTIMATES FROM 
"LAND USE PLANNING" 
TOTAL NO.=80 
Ir. 
0 
0 
MAXIMUM PERCEIVED NOISE LEVEL, PNdB 
Figure 5 
6 59 


Community reactions to aircraft noise - Noise measurements

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server