I FAA DS-67-18

j DESCRIPTIONS OF FLYOVER NOISE SIGNALSPRODUCED BY VARIOUS JET TRANSPORT AIRCRAFT

TECHNICAL REPORT

4D

tIN% A V/

[ August 1967

D D

rDwight E. Bishop ,LL 1-- k

Bolt Beranek and Newman Inc. -15808 Wyandotte Street

Var Nuys, California 91406

i Under Contract FA65-WA-1260

I DEPARTMENT OF TRANSPORTATIONFEDERAL AVIATION ADMINISTRATION

Aircraft Development ServiceWashirton, D.C. 20590

CLIARINGHOUSE

---- , j"r- :

DISCLAIVU NOTCE

THIS DOCUMENT IS BESTQUALITY AVAILABLE. TUE COPYFURNISHED TO DTIC CONTAINEDA SIGNIFICANT NUMBER OFPAGES WHICH DO NOTPPRODUCE LEGIBLY.

REPRODUCED FROMBEST AVAILABLE COPY

L TEC-VNICAL REPORT VDS-67-18

Contract No. FA65WA-1260

DESCRIPTIONS OF FLYOVER NOISE SIGNALSPRODUCED BY VARIOU3 JET TRANSPORT AIRCRAFT

By

Dwight E. Bishop

Prepared for

The Department of TransportationFEDERAL AVIATION ADMINISTRATION

Under Contract No. FA65WA-1260

By

BOLT BERANEK AND NEWMAN INC.15808 Wyandotte Street

Van Nuys, California 91406

This report has been approved for general availability.The contents of this report reflect the views of thecontractor, who is responsible for the facts and theaccuracy of the data presented herein, and do notnecessarily reflect the official views or policy ofthe FAA. This report does not constitute a standard,specification or regulation.

Ii ABSTRACT

i| Descriptions of aircraft flyover noise signals in termsof "effective perceived noise levels" or "integrated per-ceived noise levels" call for a more detailed analysis ofthe recorded aircraft flyover signals than has previouslybeen required. To provide a basis for comparing theserelatively new measures vith other flyover noise measures,

i -this report provides descriptions of maximum levels andtime durations for 45 flyover noise signals produced by avariety of turbojet and turbofan transport aircraft in currentairline service. The descriptions are based upon one-thirdoctave band noise spectra determined at one-half secondintervals throughout the flyover time histcries.

? tComparisons are provided between integrated perceivednoise levels, effective perceived noise levels, perceived

- noise levels calculated from the maximum third-octave bandnoise levels occurring during the flyover and N-weightednoise levels. Comparison of various duration measurementsand corrections are also presented for durations measuredat levels of 10 dB and 20 dB down from the maximum flyoverlevels. Comparisons indicate high correlation among manyof the different measures describing maximum noise levelsand duration.

!I"

i

[

[ i

Il

TABLE OF CONTENTS-

I. INTRODUCTION . . . . . . . . . . . . . 1II. DATA PRESENTATION .......... •••••• 3

A. Outline of Measured Quantities . . . * * . . . 3B. Data Tabulation . ..............

III. FLYOVER DATA COMPARISONS .. ..... ..... 7

REFERENCES 9TABLES

FIG U7 ES

APPENDIX A . . . . . . . . . . . . . . . . . . A-i

APPENDIX B . . . . . . . . . . . . . . . . . . . . . . B-i

iv

Ii

I I. INTRODUCTION

3 In developing proposed noise criteria for the certificationof new jet aircraft (Ref. 1), several relatively new measuresof takeoff, approach, and sideline noise levels have beensuggested. These measures generally require a much moredetailed analysis of the aircraft noise signal then has beenundertaken previously. Among the flyover noise measuressugsuted are the "effective perceived noic levcl" sn3 the"integrated perceived noise level". Both measures may becalculated from one-third octave band noise spectra determinedat half-second intervals during a flyover and both measuresinclude, directly or indirectly, adjustments for the presenceof discrete frequency components and for the signal duration.I i contrast, the most common measure of aircraft noise incurrent use is the perceived noise level calculated from themaximum octave or one-third octave band noise levels occurringduring the flyover. This measure is calculated from a singledetermination of octave or one-third octae noise levels fora flyover time history. (Ref. 2, 3)

Descriptions of the flyover noise signals for currentaircraft in terms of the effective perceived noise level orintegrated perceived noise level are not generally available.In order to provide a basin for comparing these measures offlyover noise with other measures in more common use, BoltBeranek and Newman Inc. (BBN) undertook a detailed dataanalysis of a number of flyover signals, as authorized underFAA Contract FA65WA-1260, Modif. 8. This report presentsresults of the analysis of 45 flyover noise signals producedby a variety of current turbojet and turbofan transportaircraft. Both takeoff and approach flyovers are included,with samples of most types of commercial trtnsport aircraftin current widespread use in this country. The recordings,for the most part, were made at civil airports during takeoffs3and approaches of aircraft in regularly scheduled operations.

The data analysis requirements imposed by the definitionsof the effective perceived noise level or integrated perceivednoise level introduces the needs for flyover noise signalrecordings covering a relatively large dynamic range. There-

- fore, a large number offlyover noise recordings were obtainedand screened in order to obtain relatively 'clean' recordingswhich were finally analyzed.

Section II of this report briefly describes the variousmeasures of flyover noise signals considered, and presentsthe results of the data analysis in tabular and graphical form.I

'I

Data acquisition and reduction techniques, and instrumentationare summarized in Appendix A. The scope of the study didnot allow for detailed comparisons of the various measuresof the flyover noise signals. However, some of the differencesand similarities are briefly summarized in Section III.

J

A-21 i

-1

IK)

-2- i

-%

~N

II. DATA PRESENTATION

f A. Outline of Measured Quantities

The one-third octave band eound pressure levels at centerfrequencies from 63 Hz to 10,000 Hz were determined at eachhalf-second interval during the recorded flyover time histories.In addition, the N-weighted sound levels were measured at eachhalf-second interval.* The N-weighted levels were includedsince previous studies had indicated that the maximum N-weighted sound ILVe!S are well ccrrelated with perceived noiselevels calculated from the maximum octave-or one-third octaveband levels occurring during the flyover. Previous study hadalso indicated that the time durations determined from N-leveltime histories should be similar to those obtained fromperceived noise level time histories. (Ref. 3) The dateacquisition and analysis procedures employed are summarizedIn Appendix A.

1. Maximum Flyover Level Measures

From the one-third octave band noise spectrumdetermined at each half-second interv&l, a tone-corrected perceived noise level can be calculated.This quantity will be identified in this report 9sPNL (0.5 sec). This quantity is determined as follows:

MI (0.5 sec) - PNL (1/3 OB) + F (1)

where

PNL (1/3 OB) perceived noise level calculeted fromthe noise spectra according to thetables and procedures given inRef. 2. (This is the usual procedurein calculating the perceived noise

r level, without corrections fordiscrete frequencies or duration.)

F - correction for discrete frequencycomponents determined by the proceduresand tables of Appendix B.

The N-weighted sound level is the noise level cbtalned afterpassing the flyover noise signal through a frequencyweighting network having the inverse of the 40 hoy noisinesscontour.

-3-

From Inepection of the FVL (0.5 Sec) values oc-ucring duringa flyover, the maximum value way be determined. This maximumvalue is identified as PNL(max). Similarly, from inspectionof the PNL(l/3 03) velues, the maximum value of the PNL(1/3 0B)can be identified; this value is designated as PNL(I/3 0B)m .

maxi

A third "maximum" value of interest is the perceived noiselevel (,?ithout discrete tone corrections) calculated from themaximum one-third octave band noise levels occurring at anytime during the flyover. This quantity corresponds to theper yeivad noise level quantity value most usually reportrdfor previous flyover data. A fourth "maximum" value wasalso determined -- the maximum N-weighted sound level.

2. Time Duration

The time duration of a flyover noise signal may bedefined as the time, tk, in whioh the signal iS withinKdB of the maximum signal level. Time durations weredetermined from time histories of the Pt (0.5 sec),PNL(l/3 01), and the N-weighted sound level. Durationswere obtained for values of K equal to 10 d9 and 20 dB(i.e., 10 dB and 20 dB down from the maximum levels).

3. Effective Perceived Noise Level

The effective perceived noise level is defined as:

1iLef f = FNL(max) + D (2)

'here D = a time duration correction determined eitherfrom

tlO t 20D 1u0 log - or D2 0 10 log (3)

4. Integrated Perceived N:oise Level

The integrated perceived noise level has also beendetermined for the flyover time histories. The integratedperceived noise level, PNLint is defined as the addition,on an energy basis, of the PNL (0.5 sec) values over aspecified dynamic range:

L-- -

I_

r

Pi -1L(max)

PNLn t lO log Antilog PNL(O.5see)_ (4)PNL(max)-K

The summation indicated by Eq. (4), was performed forvalues of K equal to 10 and 20 PNdB (i.e., over theuppermost 10 and 20 PNdB of the flyover time history).

1. Data Tabulation

Thr zeasures described above are tabulated in Tables Iand II for each flyover. In each table, aircraft areidentified as to engine type (turbojet or turbofan) andoperation (takeoff or landing). The slant distances (i.e., theminimum distance between aircraft and recording microphoneduring the flyover) are also listed in each table.

Table I lists the various measures of the maximum flyoverlevel. Two value* of the effective perceived noise level andintegrated perceived noise level are listed. One value wasdetermined considering the upper 10 PNdB of the flyover noisesignal (K 1 10), the second, with the upper 20 PNdB of thesignal considered (K - 20). Also listed are the values ofPNL (max), PNL (1,/3 0B)xnax, maximum N-weighted sound level and,

in the last column, the perceived noise level celculated fromthe maximum one-third octavc bond sound pressure levelsoccurring at any tine during the flyover. (As noted earlier,this last quantity corresponds to the perceived noise levelas most commonly calculated from flyover data.) The, tablealso lists the time, with respect to an arbitrary reference,at which the PNL (max), PNL (1/3 OB)max , and the maximum

N-weighted sound levels occurred during the flyover.

Table II lists time duration data fox each flyover. Shownin the table are the time durations at 10 dB anr 20 dB downpoints as determined from the PNL (0.5 see), PNI, (1/3 OB),and N-wighted time histories. The time dturation correctionsof Eq. (3) are also tobulated for the NL (0.5 see), PNL(1/3 OB) and N-weighted time histories. Also shown are theratios of the 20 dB- to 10 dB time durations.

In several instances, duration information at 20 dB downpoints is bracketed in Table II. The brackets indicate

3 possible error, due to insufficient dynamic range in someof the third-octave band time histories.

S,-5-

i'igures 1 through 45 depict noise spectra and time historyinformation for each flyover. Th± upper chart in each figureShous two third-octave band spectra. One is that occuriringat t~ie time M L (max) occurs, the second, the ruaxlmum third-octave sound pressure levels occui'rin, at any time during theflyovcr. The lower char in each figure shows the time his-tories for the PNL (0.5 see), PNL (1/3 0B), and the N-weightedsound level. The chart also soh:ws the calculated perceivednoise levEl of the background noise level for each flyover. 4This back round noise level is governed by the ambientacoustic noise level existing in the field plus the electricalfloor of the recording-playback instrumentation.

The difference between the PNL (0.5 see) and PNhL (1/3 OB)value shown in the time history charts represents the discretefrequency corrections determined by the calculation procedureof Appendix B. The variabilit'y of third-octave banl noiselevcls determined from 0.5-second samples is high at very lowfrequencies with varlabilit. decreasing as frequency (andbandwidth) is increased. (Ref. 3,4) This variability atlow frequencies gives rise to apparent frequency irregularitiesin the spectra reoultinu in small discrete frequency correc-tions even for some spectra which would be judged in listeningtests as broadband. Th large discrete frequency correctionsare, of course, govern(.u by the existcnce of strong discretefrequency components in the frequency range generally above1000 HZ.

The N-weighted sound level values listed in Table I arebased upon the electrical output from the data reductioisystem, plus a normalization value based upon previouscorrelations of N-weighted sound levels and calculatedperceived noise levels (base on the maximum levels occurringdurinr the flyover). In preparing the time history plots ofFits. 1 through 45, the N-weighted sound level values havebeen reduced by 10 dB to increase the ease of reading thecurves by eliminating overlap among the various time histories.

-6-

L!

JT III. FLYOVER DATA COMPARISONS

The scope of our program did not provide for detailedexamination of the relationships and correlations betweenthe v rious measures of maxim.im noise level and timeduration. However, we did take a first order step inexamining the relationship between measurer, by computingthe differences between various level and duration measures.Table III presents a tabulation of mean differences andstandard deviations of the differences for a number ofcomparisons. Separate mean and standard deviation valuesare shown for turboJet and turbofan takeoffs, and for turbojetand turbof&n landings. The upper portion of the table listscomparisons for various measures of maximum levels; the lower

- portion, various measures of time duration.

* The first row of Table III compares the differences in theintegrated perceived noise level and the effective perceivednoise level, both determined over the top 20 dB of theflyover signal. The integrated perceived noise level averages7 to 9 dB Greater than the effective perceived noise level,with standard deviations of the order of 1 dB. 'The secondrow compares the differences between Integrated perceivednoise level determined ovrer the upper .0 and upper 20 dB ofthe recorded time histories. The mean differences are ofthe order of 0.3 dB. . In fact, the maximum differencegor any of the flyovers is 0.5 dB.

The next four rows in the table compare differences betweenother measures of maximum noise level. In Row 3, thedifferences betweer PNL (max) and PNL (1/3 0B)max , represents

differences essentially due to the discrete tonE correction.As expected, the differences are largest for landings,particularly of turbofan aircraft.

The fourth row compares the PNL (max) values with themaximum N-weighted sound levels. The mean difference variesfrom 1.5 to 4.4 PNdB. Row 5 compares FNL (1/3 0'na with

the N-weighted sound levels. The mean differences are sisll,ranging from 0.6 to -0.8 dB, with ste.ndard deviations of theorder of 1.5 dB, indicating quite good correlation betweenthe N-weighted level end the perceived noise level calculatedfrom noise spectra determinel at 0.5 second intervals.

I The next row (Row 6) compares PNL (max) with the perceivednoise level calculated from the maximum third-octnve bandnoise levels occurring at any time during the flyover. Theigreatest difference is found for the turbofan landings,

III

UI

resultinZ, of course, from the relatively large discretetone corrections applied in computing PNL (max) for theturbofan landing data.

The seventh row compares the differences in perceivednoise level calculated -'rom the third-octave band spectraa' any 0.5-second interval witli the maximum third-octavebands occurring at any time during the flyover. The meandifferences range from 2. to 2 dB, in accord with previousexperience. (Ref, 3)

The remaining columns in Table III present comparisonsof Cdifferent time duration measurements. Rows 8, 9, and 10compare durations measured at 10 dB and 20 dB down from themaximum levels. The mean differences range from +0.7 to-0.8 dB. The mean duration correction calculated from 10 dBdorn data is greater than the 20 dB down correction forturbojet takeoffs, and turbofan takeoffs and landings, butnot for turbofan takeoffs.

The remaining four rows in Table l. cmpare the variousmeasures of time duration. Rows 11 and 12 compare durationdetermined from PNL (0.5 sec) data with that determined fromthe PNL (1/3 OB) time histories (i.e., time histories withand uithnout corrections for discrete frequencies). The lasttwo rows compare the durations determined from the PNL (0.5 sec)time histories and those determined from the N-weighted soundhistories. With the possible exception of the turbofan take-off data, the differences in duration corrections are relative-ly small, averaging less than 0.5 dB. Standard deviations arealso of the crder of 0.5 dB indicating quite consistent agree-mait among the various duration measurements. Mean differencesand standard devlations are somewhat greater for the turbofantakeoff data.

In Zeneral, tnerefore, toe duration data indicate that:a) for moat current aircraft (with the possible exceptionoV some turbofan aircraft takeoffs) di.fferences in determin-in duration corrections at either 10 dB or 20 dB points aren..t large; and, b) the determination of time durations fromN-we,nted sound level time histories yields good estimatesof the duration determined -z time histories of PercelvednoIe levels calculated from third-octave band spectrum at0.5-icond Intervals.

Jo

I

lREFERENCES

Ii 1. "Revised Draft of FAA Noise Certification Procedure",FIA, January 31, 1967.

2. SAE ARP 865, "Definitions and Procedures for Com utingthe Perceived Noise Level of Aircraft Noise", 19.

3. D. E. Bishop, "Frequency Spectrum and Time DurationDescriptions of Aircraft Flyover Noise Signals', FAATechnical Report DS-67-6, 1967.

4. W. J. Galloway, "Frequency Analyses of Short-DurationRandom Noise", Sound, I, 31-34, Nov - Dec 1962.

I"9

r

I

!-9-

A/

04 I I .- O - 0Nc TIl C, .a)C )Mur r i ,Q04N02-r-- 0f40fl CfO-- CC)-~4C 0c0Ju'-t C70 cnt0~ (4.t iC

t- .U M4)(j C, Z

IL.

I00D4

Z* 02 1: a - NC ' sCg

4. ~ ~ ~ ~ ~ ~ 7 c.-. -41huV7 r~)($)t~)--~ L%,)

o ~ ~ ~ ~ ~ ~ c -j- cj. r4(l CJ4-rCCC,- C0),r4 .. 4- % i 4 ') 44-. '.4 nr-4-ri4

)

N 1

C-4 0 C 0' C2~'x2~\faC fl I' 0 tOW C C

(Y) i C-c -- -. c -or-N-Y) 00 C' 0 .

rlMX r 74>1) Z o_ 4y) -7 0- C.r--- Co --7- -lO C4 lr- -

4)( 4,4 , 4

-3 L3 CO

.2CW IW' )f4 a, 0 0 a .P2420

-c ON-4 O mC-or co4)U0(1"1N U ) C

04. 90 N- - .0C Q 0-U ( 0 C 3 V

43430.42 .gm ~ ZuCvu, 021 02)20 >> ccS r-0" ' u~±u0y0[ ~~ 3 g%~$f~> >t$~I j g.2t2 -

P. d- t- * CO. C, 0 CDr D r r)7L\o C r\1 1 -T04 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ r m. m4 -n m rn "I(0. 220. -0.CC Ia- 4 4 -CO'C-C0 NcC --

.,~ 4. 4. ~ C- 0 CC.4C4Cj..~C4C0C(Cj~~4ri vm.-.-.'-.x .~;22 rC:44-i-O,.Al

44 4r1~-r~rr4 4-,r~-4r fl444-4-44 ~4-'~'

hliO<lO ~r- r- +Y . -e ,riCJ9 '-rI , cx-i u ..4 Il, ('-r (,S. r ., ,, - rj . ,4 .-

D Q *CJ -laCJ0 0-C 0 0C-,Cc.'-.0e.~-e~ C 4 C31

r Crci4

3 ff.-v r11 W -a 0 CO I C' i .

FN-r

(i " c" ; . . . •. . .- . . . ..."

: C4 f. O C , ,C.u. -,- c- C) C.,

Ivc , .... _.

7"+ i- " '::-a :" ,. " , , .",J,,' . .,, .. . ., , . . . . . . . . -- . , . . .. .' _- .

(-em LcC'' CJ.- ~r C -,.,. e . e I n ,C,- -i1-c i i i -i i i . n7"

1,-

I ....... .. ........... . . . . . • , ..; ....; .. .

c C r- - ('Cdifl e-r-c I C ' C , lr -cI p 4 C - 0i,]C J""Jr ' "Ji i'r-I lr I 4.--cr r -i-Irr- - --

-~~~ ~ .- .c ' , ..'+ . .;-,-:...

...+ • '+- .' ..' .' ." , ' • .. + ..• . • • ". .. .- . ..-... .. . ,

< ~ ~ ~ ~ ~ ~ ~ ~ r j .. ... .- . . . . .. I ... . . . ... .. .. .. ...

zz

C) >

: -1 2 . e CIO

IC N.- -

044 +,. J..- . -- 4--

+ - ii -i-

-~c-

r-4 0 (\J C4 .-4 c 0 -i

P 0 C) N ~ H N~ 4 0 C, 0; 0

0

w vi J 00 J 0 N UNJ c N 0 4 CN .C .

4J -4- 0 -4 H- '-4 0) r-4 0 0 0 0 0 0 0

0

C (Th .0 0 u 'C - - '0 'N v ) r-i

G 4 O 0, (' 4 (J

'.0~~~~~~ (N N 0.t 4 C N

0~ 0 .-4 m..

H 0D 4.) 4 0 0 0 ' r-4 0)0 0 C0 0 0 0 C0 C0 g.r

mw 0 00

Q - .4 r-4 .

< C) r 40

-- c C 0 -c

F-I >400

PQ -4C-4

> 0 0.

-4~~ 0 (1,. 5r- r- 0 -0 .

(V) Q

1-0 0)r-4- (N t0 N

C/) 0 (U m0

0 4 N (J ~ iC '0 C-40 0 (D. 0j 0y' (%I~ -4, ,-

'Y) Q

IIto

*|I - -

I IA.- NOI _ -1-T

[ if11 0 _ __ N (13 I _ _ "_

10

3pcK V910003011 s am

I ii _-

U01 1 I j I ,~ I~*~ IN~ ) F Is . ,

6 3 125 20 So 1000 No 4000 11000 16000Oft-Third Ocee Send C~nF Fluque~y in .44.1

I A NOISE SPECTRUM

I _

S PNL(1/30) - F__-PNL (1/3 0)

- N-W@4#htod Sound L.'I(Mifruy Ref.)

0 lociegroud PNL (1/3 OB)

___ _ __,__ _ ___ __ ____

, IIo

_0 - 0 -0 . ,Time In "al

S. TIME HISTORY

FIGURE I FLYOVER NOISE SIGNAL SPECTRUM AND TIME HISTORY - S0lING 7203 TAKE OFF, 370 FEET SLANT DISTANCE

I!I 00

90

I - ~Mm.. LawIt Duting FIlo".rtSwchr.n VA4.. PNL (1/3 0S). F is Wi,.m

70,63 125 230 50 1000 00 4m 800 16000

One-Th~td Octev. IwW C.M,. fq~v..cy in merftI A. NOISE SPECTRUM

p 120.

a-A

-PNL (1/3 OS). F-- PNL ('/3 Of)

- N-WelIht d Sc d Le".I(A*Itroy W.)

0 lecqrmd PNI. (1/3 OS)

010 20 X0'lu.o In amnd

111 TIME HISTORY

FIGURE 2. FLYOVER NOISE SIGNAL SPECTRUM AND TIME HISTORY - S1INrG 720TAKE OFF, 530 FEET SLANT DISTANCE

0

- Mwn. Lowto DutIFQ Flyc~.rI-

U vOm-Third Oct.., Sond C.opm F.tq..ncy ir rf

I A. NOISE SPfCt*LUM

13 Ir 1 1- PNL (1306) - F

1-0 PNL(I/306)

- welg).tod Sou..d L"I

0 Sqtd~g PNL 01/3 06)

110~

Po If c-d

B. T,Ml HISTORY

FIGURE~ 3. FLYOVIR NOISE SIGNAL~ SPECTRUM AND TIME HISTOlY DOUGLAS DC-8I TAKEOF;, 700 FEET SLANT DISTANCE

1

120' -k.P L(/ 11 shw

//

7 .I I , . , -I I .

63 Vo. .N Soo 100 2 P sm 1

A. NOISE SPfCIRL.M

PNL i/3 -6)

NCcromi PN i I7 1, 1 I

- - $ PPe 4Lv (1/2 IN I (I-1U F It - -l,

0 0-0.0

T: " In "Von

4. TIME __ 20R

FIGURE 4. FLYOV(* NOISE SIGNAL SPECTRUM AND TIME HISTORY -CONVAIN 560TAKEOPF, 506 PEET SLANT DISTANC

-. - 11-3-*..-- F

II

* 70

* - - ~~Simocf #~an PNL It/3O)*FI

I ~~0 6043 125 250 Soo lo MIX0 20 0 M NX 6D

Orw-Third Oct*" Iknd Comet fpqs4.cy irf

A NOISE SPECTIUM

9020

3I (11O 08

I IO4 of- (1 01

70 i-- NI/3*. .1 ..-

30 to 203

3 S. TIME H.ISTORY

FIGURE S. FLeOYER NOISE SIGNAL SPECTRUM AND TIME HISTORYV CONVAIR 8803 1 ~AKEOFF. 820 FEET SLANT DISTANCE i

110

Spe irmYg I l(O fu

I~N i---f10--)-jF110 PN Ir*11

-j I 0A, PNL)I,-306F PN (1/ Oi

! 0 I

20 21 4 0

T, in -!nd

S.PN TIME6 HISOR

110T K( FF 126 FEE SLAN D -- NWgE ~ dS~d

I

0

sp*CtMvm YA PINL (1/3 0S) F Is Ma. n

0 1 1L 'L I -63 125 i,- 500 00C 2m)0 40 000 16=~3,n.-hhl Oct... lad Cont, v' in Kerz

if A. NOISE SPECTRUM

10I K .".0

.E OD

PNL (:/3 06). FPIL(1/3 06)

,0 L05

Fi E FILYVER1 NOISE SIGNALSPCRMADlEIIRY AAVL 6tAKltQ-F,2314 rFT SLANT mSrANCE

;10~

IE100I

Spo-Vo -t4 1/-09) IF W----r

60 ~j L k I I i , I

63 125 250 500 1~ ODO X~m 400 0=~ 160O,..- I I, Octao. Bond Cet* Ffq@ yi.Hit

A. NOISE PEC7UM

lao, 0, 3..- I

FNL iI/OS,.

0 b *,o, .dI.na PNL (1/3 06)

.5 100 L , ---- I

I V

10 20 30 4Tie, in secorwi

B. TIME HISTOPY

FIGU.RE S. FLYOVER NOIlSESIGt4AL SPECTRUM AND TIME HISTORY - OEINCQ 707

AID.

so L

62 -15 2I 0 3O 200 0 I V"0 V-Th1Pi t O 8) bc i Cate .rq rc I, i

I A NOISE iP(IC1RUM

'I

IIi ~ PNL il'3 Oil) F

-- qL 0/3 OBI~ ~~~F- N-Y~gIhtod So~,,d LesII (Arb;frary Ref.-)0Backg~o-n8 PNL (1/3 CA).

10 2 04

S. TIME HINICF c'

FIGURE 9. FLYOVE9 NOISE SIGNAL SP(CI UIV AND TIME HISTORY -BOEING 7209I TA E OlFF I 20 FEE S ANT DISTANCE

IIt

90 A I

a I0

.3i~t I A9 PL(/ CC-FitMxs I I , I I I I , , , I

61 705 2__0 5w_ _00 200_wo 60

12 -N (1/ O N (/ k)*

N-WeigIhted Sov"d L.v.II ritar Reft

-0 llo ro~~nd PNL it,;3 06)

c too

70

B. TIMO HISTORY

FIGURE 10. FLYOVER NOISE SIGNAL SPECTRUM AND TIME HISTORY -ROEING 7205

66,FE L NTZI'A C

0

I 60t- Mo.. Levels ODflIt Flyov.wr- c- ) Mo,. PNI. (1/3 06) F is m I

1 063 125 250 500 10 ODD 0 m 0 A" 0a0 16000

3A NOISE SPECT1tUm

120 _

11 - -N-W~ighfod o dLa(A~~itr ory Rtf.)

0 o 1 g~~ d PN L I,3 0111

70 ------ 4-

600

IGURE I I FLYC' Eg N015E SIGNAL SPECTRUM AND TIME HISTORY -DOUGLAS DC-8-5OTAKE OFF, 1160 FFTSA TDISTANCE

IIV/ m

70~ 4

60 11 -- 04 o ws L. w.I. Flyo-,

-- A4.nPN1 (1/3 06) * F is

63 125 250 500 1000 2000 4000 8000 160O

A. rNOI(E SPECTRUM

0 6od-.d PNL (1/3 OS)

go

10 20 30 40

b TIM~E H ISTO Y

FIGURE 12- FLYOVE.R NOISE SIG NAL SPECTRUM AND TIME HISTORY -DOUGLAS Dr-p5,

iAPAQFF, 1325 FEET' SLANT DISTANCE

I 00

I ~90 ___ _

i __II

00

I' LF

rA NOIS SPEZTum

IIt

A ,

-t A--

____* A,~ km .~

("bitry Ref'i

0 PL (1,2 PL F/3 06)

13 3, 10 20 30 AO -0 60 70

8. TIME HISTORY

FIG :PE 13 FLYOVER NOI E SIGNAL SPECTRUM ANC TIME HISTORY - DOUGLAS DC-8-50

TAKEOFF, 1343 FEET SLANT DISTANCE

If

1I

soII

ItI

A** P N OI )/ E0 TRUF M

63 125 25,0 So :w 00 01sw 60

1 01

70 N-W.ighIod So,. 'd L"14 +

0 Scq-ond I NL 11/3 C*]

0 3D 40 50sawnI . o

9. TIME HISTORY

FIGURE 14. FLYOVER NOISE SIGNAL SPECTRUM AND TIME HISTORY -BOEING 727ijA~tVtf, i5VQ FEET !LANT PISTANCE

3 ~100 _

0

30 77 111163 1 t~~Yie N 130)*F* 25 250 500 1000O 2=0 40D00 80C 16000

0n.-Thid Octave Bond Cente, F,.q.cy HomT

3A NOISE SPECTRUM

g I 1 [

110I

0 /N ' '/0

- ok c FNL (1/3 F )

-0 0 - - .NL (301)_____ITi In Bock~rod

~~10~~ TI HISTORYtdB 3

FIGJRE :5 I'L Y'EP NOISE SIGNAL SIPECTRU~' ANDI TiAAE HISTORY -BOEING 727

7AItE OFF, 530 FEE T SLANY DISTANCE

It

a 706uI

Sp- $ ct-.. Y~ ol PN I. (1/3 CO) - f i. , o .

ElA. NOISf S.'ECTRUM

120 _ _ _ __ _ _ _ _

I; L

__ ~ PN 1,1/ C-6 --- f 1---

70 PN 1/ l

0 soims PN.I1/ 8

0 I 0

LI 1II FIT RFI UE1. FfVqN IFSG A PC R M A V IEmSO Y N EN 2

rr 10M) 9!.

II1

3 60

- pct MO , eN.I (1 F~o iift

63 125 250 5w0 1~ DD 40D0 MO 16000OeTidOcto'~. Band Cent., ~ .

JA NOISEt SPftCTRujm

I tio-~

I00Il 9d

q%

PNL .1!300)70N-W qkI.,d S.und L..qI

TA..LGFF. 770 FEET SLANT DISTANCL

F4

0

70

40 L- t---'-*~-1, I~..S dC 1. l<,e ,: *I

- ~ ~ ~ ~ ~ ~ ~ ~ N 11 0p8')' -.,* FN I' S

P0 L ii 31 0O',-Th.,d ~ ~ ~ ~ ~ ~ .- OLo.SoIC-.,F.q. , *

0- PNL -1 3306

0, f. .gt. ~~ 0.

AAJV

a TIME ISICVa,

YAVEOF,, 1 323 FEET SLANT DiSIANCE ~ !~C' .

110

Spc, It P L i3 t 4

63 15 2 't) 5~o 15 ?0u, " 1~ 6OO2 lOOOn-Th.,d to Kr Cenfv, Freq,..c, r. HfrtZ

1 4 NO.ISE

122V

flN3 (1 '-

N-egio - et

0 Ikl dPL / 6Ti" i, 4-S

I V-E F C EF ,IS ; rAL S E T U f- T M i T P O V I

7 41_ F >F,9 'F FT 5 N 1T

70

-- S9,. VA~ PNL (1/3 CIS) *F ii wo-

63 125 250 500 '1" ? 40D0 8000 16000

A. NOISE SPECTRUM

PNL 0 1/ /3 8)

-C -13 0Ic 2 30 43 so 60

B TIME HISTORY

F IGUIE 70. F iYCVE NOISE SIG NAL SPECT8 JMY AND TIME HI STOR Y -CONVAIR 790,Inr Es~r C;F tti i LN ;E E 7

[1100

M- L-.D ig ioo

- - Spectr."m Me~n PNL (1/3 09) - F .

- *T)i~ Ocrant* bafd Coe Fr*4q.'cy I. Hertz

A. 'mO'St SPECM1AJ

90f------I I

2 ~d70*

PN 1/3COS

20N30 ,0 5c 60

00 Tocgi-n iNL (1/3 0

B. Timt HISTORY

FiGAE 21 FIyOV~F NOISE SIGNAL SPECTRUAA AND I-A[ HISTORI' BACITAKEOFF, 1328 FEET SLANT DISTANCE

if 100 __

U9

70

C5

401 I I I I . I , ._

On..-ThIrd Octm. 4.1 Corte, hmqs,.cy i. Hertz

A. NOISE SPECTRUM

110 __________

-~ -~----~ ± -- NL (/3 06)WV *N.-W.,ght~d So..d Lo"I

0 Ied'4 ., -d PNL (1/3 06)

10 x 30 40 50 60 70 so 90

96 TIME HISTORY

FIGURE 22. FLYCOVER NOISE SIGNAL SPECTRUM AND TIME HISTORY -BAC IIITAKEOFF, 1122 FEET SLANT OISTANCF

0

-- M . LsAol D.NLr Flyo..,

-- Sp*,tr. o PN (1/3 06). F I, ma '

O"~-Th;,d OctU'v. lo~d Conte, Fr..nc 1n 4002

[A. NOISE SPECTRUM

-10 N-Weighted So-d L..,l

[Abtar ~.

v

3 0 20Ti304

I . TIMf HISTORY

FIGURE 23. FLYOVER NOISE SIGNAL SPECTRUM AND TIME HISTORY OEING 7703 LANDING, 020 FEET SLANT DISTANCE

IT

100-_I

70_

60 __ ____ - __

50 __ ____

-Mm.. L.ewIs DwiqFyI-- Spettvm V*o PNt (1/3 CI) * F IB Mdeswm

63 125 230 So 1000 2000 4000 m 6000on-Th4d Octqa.. tond Cefitot Irtq'..n in Hewt

A. NOISE SPECTRUM

120

1101

PNL (1/3 06) F

I-- -0---- PNL (1/3 OS,- - - N-WolgI.Ied 56,,nd Level

(Artdho~y Ref.)j0 bockm.d PNL (1/3 b

0 0 20 30T m rC ~

B. TIME HISTRY

F:.1:RE 24. F-YOVER NOISE SIGNAL SPECTRUM AND TIME HISTORY -BOEING 720LAND~ING, 890 FEET SLANT DISTANCE

0

- Ma. Levels Durng fly I

Ono-Nir.d Octave Son Cete Freque.ncy in mr

jA NOISE SPECTRUM

PNL (1; 3 0) F

-- PNL (1/3 09)

Ila Axb:tre Ro.)

RIVA

600 20 40

ET1.1HISTORY

FIGJRE 25. FLYOVER NOISE SIGNAL SPC,-TR UM AND TIME HiSTOT Y DOUGLAS DC-8L ANDI NG, 1 'C FEET SLANT DISTANCE

r5 I I

II

MO. L.Ivel, Dv P.c--S p o tn ' V A e er P N L ( 1,'3 S) * F i-

63 125 250 500 1000 2000 0 0000 16000Or*-r'r;d Octavo bond C ewt Frq, ,ncy ;n Hertz

A NOISE SPECTRUM

120 1PNL (1/30111) F

I I- PNL (1/3 0)

110 IAI . . . . -W g td So u.nd Level

1 0 lcc,..,v PNL (1/3 CA)

-" 90 ,.' ^1_ Ii I_ _

lrI ,' I

'I I I

_ _ _ _ I__70.

_ _ _ _ _ _ _ _ _ _ _ _ I _ _ _ _60- _10 20 40Time it, second,

B IME HISTORY

FIGURE 26. FLvVER NOISE SIGNAL SPECIRUM AND TIME HISTORY - DOUGLAS DC-6LANnING. 1020 FEET SLANT DISTANCE

- -- ---- ---- ---- --- --- - - - - - -- -'--

IoI0

rl60

tiOno-third Ocro" bond c~et, F *qvncyi

itA NOISE SPECTRUM

~. 110

too___

I 70S

PNL 0 13 0) F

60PNL (1/3O)

(Arbitrary Ret.)

I~~~ ~ Tln0od Id,.qd PNL (1/3 OS)]

LANDI NG,990 FEET SLANT DISTANCE

IFI

I0

- - Sjiwctr'n Ywi'. PN,. (1/3 06)'F il i tiom

A. NOISE SPECTRUM

120

I - N-VeIghted So~ Ls,iIl

0 Ibchqo.nd PNL (1/3 06,

z J

.t90 N""

I llI

0 10 20 43Ti" i. c. n

a 7IMI HIISTORY

FiGuRE 28. FLOVER NOISE SIGN.AL SPEC7RLM AND TIME HISTORY -CONVAIC 8V

LANDI NG. 960 FE EI SIAN7 UI I~

5. ~~~ ~~~60 ___________

" ~ 4N SpetVTVan PNL (1/3 06) F is Mi.,

I. ___1 __AgI_, .____ I_,__I____

Or.-Thild 0Oct.. Send Cwnt, Fs,".cy Hif

A. NOISE SPECTRUM

* 7> I

PNL3 Ct)\ - N.W*ghtqd S.4,d Le";~

0 r~kvi fr4 (1/3 OJ)

100 - -

I ..

0 6%0 40 5.) 60$

I. TIM dIS?~y~

FIGURE 29 FLYO\,Ek N01ISE SIGNAL SPECTRUM'~ AND HM4ISTORY -CARAVEL1S 6RLANDING, 374 FEET SLANT t)II TANCE

UI

I Do

m. NlvFlo

404

63 125 250 SN IO300 2000 ow0( mm 1600One-Tht Octow 5"M Cant~w Fiq.vny ;n Mwm

A NOISE SPICTRUM

300 PNI i' (00) F _ ---- -- PNIL 03/3 09)-. N-Woig)-le 5, nd L.e.3

0lckgo n41PNL 1/5 11)

00 _

* Al

10 23 3040 50

R. NOM HISTOY

fgGIURE 30r FLY0VtR NOISE SIG3IA, SPECTR*iM AND TIM! HISTORY CARAV ILI 6R

LANDIP~l. LZ14 FIFT tAN? DISTI,.

Ito

t _______too

E

60___

- max. Lsv*lt Dvrl'g Flyovor- - Spoct. V~A-. PN4L (1/3 0) F is m -

63 123 230 500 1 ODOQa 20 4w cXJ 16000

A NOISE SPECT m

120I

I ---D

I It

900

I-A

FIGUQT 31 FLl2~ NOISE 11011A, SI'ECTOJY A0 L 71It HISTORY -B)E[,C. 707

AI.fS !C1' G2Q CIi SLAt T CC' TAI- -

AlA

707

a 60

Spctv Io 0 Soc0/3o09)d FNis((/3 O

A NOS SPCTU

I T

17 [N /306,I1 4

(Abto i .. I

0102

.E loo

r ILiir~

goLN.1I~FE LNTDSAC

II 110 --

60 4_

- Mox. Levels Dv~r FIyovef-- Spetfr. , VA*, ?NL (1,3 061- F is o n, I

NNOISE SPECTRUM

- PNL W5 3 C0S) *F

-- N-WeigIhI4d Sos'd L.

0 11"6g-.nd PNL 13 0S)

qIIC I I110

z

4 100 - 4

-5 0 10 20 30

8 TIME HISTCfiY4

FIGURE 31 F YOVE; NOISE SIGNA. SPECItUM AND TIME H-ISTORY - SEING 70I LA -DING, 775 FELT SLANT DISTANCt

I

70 Q II C

SSpect , m ._ n PNI (./3 0\) F-

63 125 20 so I0 lo 2000 AM0 8=0 1600 IOn.-Th;d Ocft-v BorW C.ps c, i .rt

A NOISE SPECTRUM

130

i i .i

1 ;/3 011)(A..betmry Ro.A

CBackgmrd PNL (1/301)

, : .----

IISI ,-!! '

i I ,:

Ti i '

I'Li. , I .

8 TME 4ISTORY

FIGURE "S FLCfO'.[R NOISE SIGNAL SP[1CTRUM AND TIMf 'ISTORY - 11CEING 7270

L AN ING. 86 5 F111 SLANT DISTANc k

-i

.1

5 ~~110 ____

spar V& PN (13 11 IF _ _ 1a~

Ii I I_ _ _ I63 ~ ~ ~ 12 2s 0 Io 00 O K 6D

OrI),r I c-eBn etrF* ni et

AI _ _!S _ _ CT

0 _ _ _

-100.I .r.gFy~.Z ~.PL(~

N OW.ighfo S d L .. SodCnI ~e,~

11 0---4 10 30I -

TY'me inIcn'

TI M HlT' *

FfGU~ 15 FLY---INL-PCPU N TI, i-TR DO G A -8 0

L I NG 3 ET .'iD SA

1001

_ _O I

-I I I-

Sp ecraa m VA * PN L (1/3 0) * F i. iI I

63 125 50 500 1000 m2000W0000On.-Third Octov. ond Com.w Frq e y Hoot

A NOISE SPECTRUM

1210

" AV , . . . --.... .

o '5^ j .

P NL 0I/3 Ol) F

9 0 . .. .. .- -- - -- - -.

70 PNL ( 1/3 06) -

N-%.igld So~.d Le"I(" itrory Rof.)

S10 20 30

8. TIME HIS.CeY

FIGURE 36. FLYOVER NOISE SIG;NAL AN r-,;;L-r~-a'jAN ING. 1 20 FEET SLANT DISTANCE

Iq

I110 __ _ _ __ __ __ __ __ _ _

I

7,0

HI__,I _- _ _

A

Ir *1 - Ma. Len.Is DwrV F o

5 0 Spectr WlM PNL (If3 0 ) F s s , irn

OW-Th4dr Octove Band Conler Fetiquncy in Hartz

A NOISE SPECTRUM

120__ _ __ _I [

110- Jvijt__

____ ___ _ _____ A tJivl ___1 z IIIw

ad

70 _____ - - - PNL (i/3 06,41 * FI

70. PNL (1/3 06)

. . .N -W sII tod Sound L -volJ { ,," itrary Ro f.)

0O S pe ,,. FPNL (1/3 ()

20 30 40 5Tim" in sownds

IB. TIME HISTORY

FIGURE 37 FLYOVER NCI SE SIGNAL SPECTRUM AND TIME HISTORY - DOUGLAS VC-8-50

LANDING, 480 FEET SLAN7 DISTANCE

110

r 1~0o _ _ _

60 __

- - ct V~ PNL (1/3 09)-FisPA l.

163 ^1S 250 500 1000 2000 4000 5000 16000 -

A NOISE SPECTRUM

130.

- .NL1/3 011) -F

-20 FNL (1/3 06)-- N-Walght~d S-.~d L..vI ____

Ahltary Ro.)0 b~xkg,.d P NL 11 /3 06) v I-

10 1002

To in mco.,&

B. TIME HIISTORY

FiGuRE 18 FLY!OV R NO'ISF SIGiNA L SPECTRUM AND TIME H.ISTORPYffhIC.I A% IC -R.AI IANrt(.

-Al1

Il r

50

- M.... .. sCsgiI

[.Spetrv W on PNL (1/3 OUI - F is Mui.,

63 125 250 5m 0 mw .1 e 6

-. ThI i M

110 -p NL.3 e~ 0- -4 -

NL 'j3 O)

N-W -Ighrtd So ,d L e iI

(Arbitmary Ref.

*

!I

-1 __0 --- NLI/3 i+ ----.--- -4 .... -

70J

IA

10 uRE 39. FLYQVER NOISE SIG.NAL SPECTRUM AND TIME HISTORY -CONVAIR 990ALANDING. 575 FEET SLANT DISTANCE

Ii" N 1/3Oe

-a- -, -~~ .... N-e .he So*an *Le-s .0-.t-el-,. -

110.i

60 -----

50~~I - 110 12 5 00 m 00 e 60

0ra-T~i~d Octa- Sond Cents, Frqn, *T

A NOISE SFECThU.'

1201 1

I10

lIO* -------- -- -1a

4@ 1I0

90**;

L (1 0S' F7F NL 0ill 05) .* 1

N.Woig~tqd S*. d L.- l

0 Skro~nd PNL l,r3 08)

LANDING. 853 FEET SLANT 0: STANCE

r ~ ~ - ~ - - ~ ~ 100

as

0--l

A rC'SE SPkC1Nutm

I.Ito

80 -- ---------

I !

-- PNL 0/3 C

50L -Id o~dLv~ --- 4-- -- *--1,2FI L)E . F~ C,.E N:)$E SI fA j E TP N N TIV H I G

;5-1 El 3LA/3 c*;.' -

I r70

bull f7 PNL ,,3 Od f-i

I-V

IN 0 .016~ US 250 500 iCN, C 3) C A, 0 s~

On.-TI"'d~N-m--o 5-'o.d Le-'C'. Fr~~cr N

Ab,-o s- ; 1.0 F ANL 1;0

02\ FEE 5. N IT C

rI

40 1 1- 1 1 1 1. [- -I

1 3 15 2 o lw w 4, I oOn-hr ctv odCetrFo"ny; et

A. N IESETU

PN (11 051 I N'Ig tdS -dL -

70 X

_0 20_ 30 -j---0-

B . TIME HISTORY

fIGLURE 43. FLYOVE(Z NOI'SE SIGNIAL SPECTRUM AND TIME HISTORY -DOUGLAS DC-9LA NDING, 539 FEET1 SLANT DI STANCE

0

60- I

50 _ _ _

- - Specrn VA PNL 41/3 08) *F is ?A ;.

63 125 250 500 1000 200C 4m0 am0 16000O,,e-hilrd Octave 66Md Center Fr c in Hwn

A. NOISE SPECTRUM

- PNL (/3 C$ -F

1- - PNL (1/3 OS)- N-Woighted $o~.d LetwI

I (A,~trory Ref.)

0 S6.kgro.nd PNL (1/3 06)

90 4vKI__ _

FIGUE FYOVE NOSE SGNA SPETRU AN TIME HISTORYSAIf

LANDI NO, A47 FEET SLANT DISTANCE

1 (~~~00__ _____ _

Isg'

60

40 1I I I I I -

63 125 2.5 500 Iwo 2000 4000 mm0 16=0One-Thir Ocrm o~.nd Cent., Freqs~ec1 rm Heftz

A. NOISE SPECTRUM

120Iz

IoIA %

60t.30O 40 50 60

9 11IME HISIC'#Y

FIGURE 45 FLYOVER NOISf SIGN4AL SPECTRUM AND TIME HISISTRYSAC III LANDING

APPENDIX A

SUMMARY OF DATA ACQUISITION AND REDUCiC:1PROCEDURES AND INSTRUMENTATION

The flyover noise levels were initially recorded in thefield on magnetic tape using the data acquisition systemindicated in the upper portion of Fig. A-i. Field recordingsduring scheduled operations were obtained at several airportsincluding Los Angeles International Airport, Long BeachMunicipal Airport, Westchester County Airport, Long Island,and O'Hare Internatior.a Airport in Chicago. A largenumber of flyover recordings were examined and selection ofthe data for analysis was based primarily upon "clean"recordings of identifiable aircraft having a dynamic range(overall sound pressure level or N-weighted sound level) of25 JB or greater.

A Kudelski Nagra III Tape Recorder, a Bruel and KJaer2203 Sound Level Meter, and a Bruel and Kjaer 2630 CathodeFollower equipped with a Bruel and Kjaer 4133 CondenserMicrophone were used to record the data. Acoustic calibra-tion signals obtained with a Bruel and Kjaer 4220 Pistonphonewcre recorded on the data tapes at intervals during the re-cordings. The pistonphone signals were analyzed later duringdata reduction as a check on system performance and as acalibration standard for the noise recordings. In addition,sweep frequency signals were recorded on the tape prior tofield use; the sweep signals were later utilized to obtaindetailed frequency response corrections for the electricalportion of the combined data acquisition-playback system.

The data reduction employed the conventional analog systemshown in the lower portion of Fig. A-1 to obtain time historiesof each one-third octave band from 63 to 10,000 Hz and the N-weighted sound level. Time markers were placed at the begin-ning of each flyover to permit time synchronization of thehistories in the various frequency bands. A writing speedof 80 mm/sec and a paper speed of 10 mm/sec with a lowerlimiting frequency of 10 Hz were employed with the Brueland Kjaer 2305 Graphic Levll Recorder.

A-1

II The sound pressure levels were ther, read from the graphic

level charts at each one-half second interval. After tabula-

t4_n3 and checking, the time-history data Incldilng background

noise level information was entered into a digital computer.

The computer calculated corre ctions for background noise levels,

calculated the perceived noise level for each one-third octave

band spectrum, the corrections for discrete frequency components

(in accordance with Appendix B procedures) end the various

measures of time du ration.

iA-

~A- 2

DATA ACQUIS!rION SYSTEM

5 & K 4220

PISTONPH ONE

II MICROPHONE WITHPRESS TO TALK SWITCH

*B & K 4131K OR 41 33MICRO?HONE KUDELSKI

-B &K 260 -TAPE RECORDER

CA1;- ODENAGRA III

FOLLOWER B K20

DATA REDUCTION SYSTEM

KUDELSKIB&K211B&K30TAPE RECORDER SPECTROMETERLEL

NAGRA 14IEOI~

FIG LIQF A.-1 NOISE MEASUREME NT SYSTEMS

APPENDIX B'.7 CALCULATION OF DISCRETE FREQUENCY CORRECTION

FOR EACH THIRD-OCTAVE BAND SPECTRUM

*1Step 1

Compute for each third-octave band determined at 0.5 secondintervals, a value composed of the arithmetic average of the

I levels the nearest two bands above the given band and thenearest two bands below.

Note:

The value for the two lowest frequency bands, and the twohighest bands is based on only the average of availableadjacent bands.

- S tep 2

Mark all bands that exceed this computed value by 3 dBor more. Recompute for all bands a second average value asin Step 1, omitting the marked bands in calculations of theaverage. (The average may now be based on several non-contiguous bands.) A discrete frequency is said to existif the SPL in any band exceeds this recomputed average valueby 3 dB or more.

SteL 3

The difference in dB between the second computed averagevalue and actual SPL in each marked band is used as the numberto enter the t-P cJee.ic;r, -ib.lc (Tale I)D-1tone correction is ut .iermined for each third-octave band thatexceeds its "average" by 3 dB or more.

* Step 4

The final tone correction for any third-octave bandspectrum is taken to be only the maximum tone correctiondetermined in Step 3. Thus, the final value of discretefrequency correction for any third-octave band spectrum is[ determined by only the "worst" third-octave band.

I[ }~

I-

N0NZ t- ON 4 r-4 N T-4 '-Ar-a4o w c -1 Nr U \ -"I ~ -v ll )r- r-

4 - -

4 r- -Ir-

4 r--i -4 r-4r

4

u ,0JI-: (,\j. N.~ 0 0 C) \ 1 0 r- C 1,4~ r4,- 0) in - 0 (y C(Y')

r- 1-4

i r-A C4,-C'(Y 0-ztLaf\.fVU D D L'u\LXD f\-D -C -0LA') N4

C- ci I'D 1-1--co )U ff 0C'\w L: 04 0Q o ~ > O o 00 0

'4> ' -4 -4 ci - )_I () CA cn3 NOW -0 U0 r-4 I'DfC -Z! 0 4 C" rZ

04

C

C* CL --~i -Z a- t-- -zc Icq' t-- o -:T -z ' L\U- N Qz 0 4 Lf\ c

r-4 r-4 (' 04 N ff)(Y') (') Cq (Y- ')CY nC ) -Z- 0140 rH

C) C',~ rJC4 .41V V000C100C14- -

E-)

*C *F- 4D

() *C~4 ('I C C N

E-1N~0-~ Q0. r~ z-0c*O c--auC) *- 1 L l 0C)O i - Y \"

C- LIN-4rC y- C\N M4 , r-Z4 10 1"\4r-4r-0 0 MI

Hy 001;O r4 . 1 L f Y r O u'A 1111 0 0

oG

> C-)

a~C 0Z 100 LAO000 00000 00000 01)0)0) 0 N 4D0 if)r-q C C)010 0 11N,00 0 L0 L-)C00

Z0 t' 4 -- 4 -. ~ 04 1 - C C'~sj C ) ULf) e-O 00 0 *r- r4 r--qN 40 (Y -01 LnC)~ 0

f--4

IlL"