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_ EFFECTOF FORWARDMOTIONON ENGINE_NOISE - -JA'C_-IJ495g) EFFECT 9F FOPWARD _OTION N78-I009]

ON FNGTNE NOISE (Douqlas _ircraft Co., Inc.)I18 p tic AOq/t_F _C ! C3CL 20A

Unclas_;3/07 50826

_ By G. L. Blankemhip_J. K. C. Low, J. A. Watki_s, and J. E. M_riman •

+++.+ DouglasAircraft CompanyMcDonnell DouglasCorporation

i+: Long Beach,C_ltfornia 90846t

.; Preparedfor

i.

: National Aerohauticsand SpaceAdmi.istration

;; NASA_LewisResearchCenter . -_.+:,+ ++

+ Contract NAS 3-20031 ;" +.'+++,% '<.::>_;r + ,+"

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https://ntrs.nasa.gov/search.jsp?R=19780002150 2020-05-08T07:39:49+00:00Z

t I I I_ _ I I I F _ •I_;p

l 1, Report N(_, 2. Government Accession Na, 3. Recipient's Catalog No.

!i NASA CR-134954

! 4. Title and Subtlt,le 6. Report Date

'.. ZFFECTSOF FORWARD MOTION ON ENGItIENOISE October 1977_ ' 6, Performing Organi_tion C_de

7, Author(s) 8, Performing Organitation Report No,G. L. Blankenship,J.K.C. Low, J. A. Watkins, andJ. E. Morriman MDC-J7708

• 10, Work Unit No.

9. Performing Organilation Name and Address,,'. Douglas Aircraft Company_.. MCDonnell Douglas Corporation ll."ContractorGrantNol

3855 Lakewood Boulevard

, Long Beach, California 90846 NAS 3-2003113. Type of Report and Period Covered w.

12, Sponsoring Agency Name and Address" Contractor Reportii: , Nationa] Aeronauticsand Space Administration •

, Washington,D.C. 20456 14.SponsoringAgencyCode

:i

.' 15. Supplementary Notes_i" Project Manager, Eugene A. Krejsa, V/STOL and Noise Division, NASAi! Lewis Research Center, Cleveland,Ohio

_i., 16. Abstract

i'.' A study was conducted to detemine a procedurefor correcting static engine data for the e.ffects_., of forward motion. Data were analyzed from airplane flyoverand static-enginetests with a JTSD-IOg'_' low-bypass-ratioturbofan engine installedon a DC-9-30, with a CF6-6D high-bypass-ratioturbofan

engine installedon a DC-lO-IO,and with a JTgD-59A high-bypass-ratioturbofan engine installedon aDC-lO-40. The observed differencesbetween the static and the flyover data bases are discussed in

_' terms of noise generation,convective amplification,atmosphericpropagation,and engine installation.The results indicate that each noise source must be adjusted separatelyfor forward-motionandinstallationeffects and then projectedto flight conditions as a function of source-pathangle,directivityangle, and acoustic range relative to the microphoneson the ground.

i. 17. Key Words (Suggested by Author(sl) _,8, Distribution Statement

!!" Jet noise Forward MotionCore noise Engine installationFan noise Excess attenuation

. Turbine noise Noise generationNonpropulsivenoise Inlet distortion

: Convectiveamt_lIfication

119. Security Classif, (of this report) 20. Security Classif, (of this page} 21. No. of Pages 22, Price"

;" Unclassified Unclassified 198.......

' Forsale by the Nationallechnlc,_l Inlo_mationServlt:e.Sl)f=11_,hehl,VlIRiIH:i72151

NA%A*( -I,," ,I*','_ h-':l)

I ' , ' ' I i "

00000001-TSA03

! I'.) ' I I I ! ;' i,jt

CONTENTS

;!,, Page

i: 1 SUMMARY 1, ,leeoeeeeeeeeeeoeoeeeeeeeeeeeeoeeoeeeeeeeeeeeeeeeeoeeeeol,

!": 2 INTRODUCTION 3'l . ,,,,,eelleeeeeeeoeeeeeeeeoeeoeeeeeee,eoeeeole,eeeeeoe

3 TECHNICALAPPROACH s_. • o,toeeeeeeeemeeooeeeoeeeee,eeoto,o, eooleoe,,.,..

;

_, 3.1 Test Configurationsand Programs............................ 5

]i 3,2 Proceduresfor SeparatingEngineNoise Sources.............. 6

_;_ . 3.2.1 Separationof loW-frequencynoise componentsfro_}_ measureddata 7

:: 3.2.2 Comparisonsof staticand flightlow-frequencynoise. 7'$

_: 3.2.3 Separationof staticjet- and core-noisecomponents.. 8

3.2.4 Separationof flightjet- and core-noisecomponents.. Io

3.2.5 Separationo_ turbomachinerynoise from static-engine•_ data.................................................71

3.2.6 Separationof turbomachinerynoise from flyover-noise: data.................................................14

3.3 Definitionof Static-to-FlightDifferences.................. isi I

3.3,1 Jet and core noise...................................15

' 3 3 2 Turbomachinerynoise 15

3.4 Correctionsfor the Effectsof Engine Installationand' AtmosphericPropagation 17

i, gi_. 3.4.1 En ne-installationeffects...........................17

3,4.2 Propagationeffects- excessattenuation............. 17

4. DISCUSSIONOF RESULTS............................................27

_ 4.1 Effectsof ForwardMotionand of Engine InstallationonJet- and Core Noise 27l e_.e.....e...+.._l.ooeo...........+..o.o_

4.l.I Static-to-flightcomparisonsof JTSD-IOgdata........ 27

_. 4.1.2 Static-to-flightcomparisonsof JTgD-59Adata........ _9

4,1.3 Comparisonwith proposedANOPP method................ 31

4.2 Effectsof ForwardMotion,Propagation,and EngineInstallationon TurbomachineryNoise........................ 3_

4.2.1 Engine-installationand propagationeffects.......... Jp

4.2.2 Effectsof forwardmotion............................ 34

_' 4.2.3 Interpretationof Static-to-Flightdifferences....... 3_/

F 4.2.4 High frequencyspectraldifferences.................. 44II i

_+ .,

'+ , _, _- +X " I ....+ .... # + .l .... , ++i i

00000001 -T.£Alqa

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CONTENTS-(ConCluded)

Page

5. STATIC-TO-FLIGHTCORRECTIONPROCEDURE...........................47

6. CONCLUSIONS......................................................49

7. SYMBOLS.........................................................B3

REFERENCES.........................................................55!

TABLES..............................................................s9 ]I

FIGURES.............................................................o6

..... ii

I ' ' ] I i...... • .... -.......... iii

00000001-TSA05

_ 1. SUMMARYT

A study was conducted to determine a procedure for correcting static-

engine data for the effects of forward motion. Data were analyzed from air-

plane-flyover and static-engine tests with a JT8D-109 l_w-bypass-ratio turbo-

fan engine installed on a DC-9-30,wtth a CF6-6D high-bypass-ratio turbofan

engine Installed on a DC-lO-lO, and with a JT9D-59A high-bypass-ratio turbofan

engine installed on a DC-10-40. The observed_d_fferences between the static

and the flyover data bases are discussed in terms of noise generation, con-

i . vectlveamplification,atmosphericpropagation,and engine installation.The

resultsindicatethat each noise sourcemust be adjustedseparatelyfor

_ forward-motionand installationeffectsand then projectedto flightconditionsi

as a functionof source-pathangle,directivityangle, and acousticrange

_ relativeto the microphoneson the ground. In order to investigatethe effect

of forwardmotion on jet noise, other low-frequencysources such as core

I noise,nonpropulsivenoise (airframe-generatednoise),and jet-flap-inter-

_ action noisemust be considered. High-frequencynoise measuredon the static-

test stand and projectedto flightmust be adjustedfor an additionalsource

of atmosphericabsorption,excessattenuation. The level and the directivity

of the fan tone at blade-passingfrequencygeneratedunder staticconditions

: must be correctedfor the reducedlevel of turbulencein flightand for the

change in the modal constituentsof the source. At frequenciesequal to and

greaterthan the fan-blade-passingfrequency,the increasedflight levelsof

turbinenoise must be considered.

I

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1 • ' i ' ! "

00000001-TSA06

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2. INTRODUCTION

The accuratepredictionof airplaneflyovernoise levelshas become

importantin the evaluationof noise-reductionfeaturesfor both presBntand

futureaircraftdesigns. Engine noise can be reducedby Using aero-acoustic

desigh featuresto reducethe intensityof generatednoise at the sourceand

by using acoustictreatmentto reducethe intensityof noise propagating

• throughthe engineducts. W_th the many possibletradeoffsfor meetinq

specifiedin-flightnoise goals, each noise-reductionfeaturemust be evaluat-

. ed againstthe potentialpenaltiesin weight,performance,and cost that it

would imposeon the engine/airframesystem. An accuratedefinitionof the

enginenoise sources(jet,core, fan inlet,fan discharge,and turbine)

relativeto the total engineand airframeflyovernoise levelsis therefore

essentialin order to properlyassessnoise-reductionfeaturesand require-

ments.

An importantconsiderationnow is the effectsof forwardflightand

engine installation._nthe airplan_on flyovernoise,and whetherflyover

noise can be predictedaccuratelyby using static-noi;emeasurementsor

wind-tunnel-simulatedflight-noisemeasurements. It is now widely recognized

that forwardmotion aridengine installationalter the mechanismsof noise

generationand propagation(refs.I through14). Contradictoryresultshave

been noted for the effectsof forwardmotion on the low-frequencyjet noise

levels (reds.l through6). The lower flightlevels in the aft quadrant

were consistentwith predictedrelative-velocityeffects,but small decreasest

and even increasesin the inlet quadrantwere not. The changeswere not

, constantwith angle (directivityangle relativeto the inletcenterline),as

had been assumedin earlierpredictionmethods. The increasedlevels in the

inlet quadrantwere neitherobservedin model-jetflightsimulation(refs.

15 through19) nor predictedon the basis of classicaljet-noisetheories.

References6 and 20 have shown that the discrepancycan be reconciledby

taking into considerationthe contributionsfrom other low-frequencynoise

source_,such as core noise and shock-cellnoise. Comparisonsof fan noise

levels (refs.6 through14) have shown that the hiqh-frequencylevel_are

significantlyreducedduring flightcomparedwith the noise qeneratedstatic-

ally. The differencewas due to the lower level of the f_n fundamentallone

.... • = .L.......

00000001-TSA07

_ ', I I" : _ i ..........I 1 ,_ I

tin the f11ghtspectraand to the lower level of the flightfan spectrarelative

to the static-projectedfan spectrafor frequenciesgreaterthan the funda-

mental blade-passingfrequency. However,turbinenoise levelswere shown to be

,. lower under static conditions. The resultssuggested(I) that the mechanism

of fan-noisegenerationand the resultantmodal structureof the sound field

" propagatingin engine ductswas differentunder staticand under flightcon-

ditions,(2) the method that had been used to projectstaticengine data to

i flightconditionsdid not properlyaccountfor the propagationof high-frequency "

noise throughthe atmosphere,and (3) the mechanismsof turbinenoise propa-

gationwas differentunderstatic conditions. As a result,the evaluationof

noise-reductionfeaturesthat uses static-enginedata projec'_edto flight con-

ditionsmay be inaccurateunlessthe static-to-f'iightdifferences(differences

requiredto correctstatic-projeCtedlevelsto the flyovernoise levels)and

correctionproceduresare known. The predictionmethod thereforedependson

(1) proper identificationof static-enginenoise source levels,spectra,and

directivityand (2) adjustmenton a noise-sourcebasis of the data for the

e_fectsof engine installation,propagation,and forwardmotion.

This reportdiscussesthe proceduresused to identify,separate,and

correlatestatic-engineand flyovernoise sources. Comparisonsof static-

'_ engine-andairplane¢lyovernoise are basedon resultsof t_st programswith

a JT8D-I09low-bypass-rati-turbofanengine installedon a DC-9-30,with a

CF6-6Dhigh-bypass-ratiotm_ofan engine installedon a DC-lO-lO,and with a

:" JTgD-5gAhigh-bypass-ratioturbofanengine installedon a DC-IO-40. The

observeddifferencesbetweenstatic arldflyoverdata bases are discussedin

• terms of noise generation, convectiveamplification, a_ospheric propagation,

and engine installation. The objectivesof this study are (1) to definethe

_ effectsof forwardmotion on static-enginenoise levelsand (2) to develop

E_I methodsof adjustingthe Static-enginedata for the effectsof forwardmotion

and engine installation.

This studywas conductedby the DouglasAircraftCompany,a divisionof

the McDonnellDouglasCorporation,under contractto the NASA-LewisResearch

,. Center (NAS-20031).

4 _

00000001-TSA08

!

,!!i 3. TECHNICALAPPROACHrl

, This sectionof the reportdoscrlbesthe selectionof the static-and

!: the flyover-noisedata bases to be used In the noise-_ourceanaly_i_. The

_:_ specifictasks were (l) to defineand to separateengine-noisesources(jot!:;_ core, fan inlet,fan exhaust,and turbine)in both staticand flyover

I data bases, (2) to define the differencesbetweenthe two data bases, (3) to

_ accountfor the static-to-flightdifferencesin termsof the effectsof engineK:

installation,propagation,and forwardmotion,and (4) to accountfor the --.

. remainingdifferencesempiricallyas effectsof forwardmotionon static-

engine noise Ievels.

3.1 TEST CONFIGURATIONSAND PROGRAMS

The flyover-noisedata used in the analyseswere derivedfrom test pro-

grams that used a DC-9-30(fig, l) poweredby two Pratt and Whitneyrefanned

JT8D-I09low-bypass-ratioturbofanengines,a DC-IO-IO (fig.2) poweredby

three GeneralElectricCF6-6D high-bypass-ratioturbofanengines,and a

DC-IO-40(fig.3) poweredby three Prattand WhitneyJTgD-SgAhigh-bypass-ratio

turbofanengines. The DC-9 programwas conductedunder NASA contractnumber

NAS3-17841(ref. 21). The otherswere funded by McDonnellDouglas. All the

tests were conductedat the DouglasTest Facilityin Yuma, Arizona. Flyover

noise data were measuredwith ground-and tripod-mountedmicrophones. Micro-

phonesmountedflush with the ground beneaththe airplaneflightpathwere

used in order to minimizeground-reflectioneffectson the low- to mid-

frequencyregionsof the spectra. In addition,microphoneswere mounted in

both inlet and fan dischargeducts of the CF6-6Dand in inlet,fan duct, and

:_: tailpipeof the JTBD-I09. References9 and 21 describethe locationsof

internallymountedmicrophonesin the CF6-6Dand the JTSD-IOg,respectively.i/:/!:. The instrumentationand the proceduresused to measure and to reduceacoustical

" data, engine and airplaneperformancedata, weatherdata, and airplanespace-

positioningdata are discussedin references14 and 21. The flyovernoise data

nresentedwere averagedover severalrunswith approximatelythe same power

setting. Table I sununarizesthe flyovernoise runs used in the fli(lhtddta

base. The static-noisedata obtainedfrom Pratt and Whitneyfor the refanned

JT8D-109and for the JT9D-59Aengineswere measuredwith 4._Sm-polemicrophones

::: 5

L..... '" ._............ 1'_, I,. , •00000001-TSA09

(I0° to 150° from the inlet)and flush-mountedgroundmicrophones(90° to 160°

from the inlet)locatedon a 45.7m radius. In the inlatquadrant,for which

flush data wer_ nnt available,th_ staticonoisedata measuredwith a 4.BBmopolo

microphonewerO correctedto the level_of grmmd-microphonemeasurementsby usin_

empiricalcorr_ctlonfactorsdevelopedfrom 4.BBm-pole-and ground-mlcrophone

noise data measured in the aft quadrant. Static-nolsedata obtainedfrom

GeneralElectricfor the CF6-6Denginewore measuredwith 12.2m-polemicrophones

on a 45./m-radius. The staticengine noise runs to be used in c_nparisonwith

the flight data hase are given in table 2. -"

Figure l(b) shows the JT8D-IO9engine and nacelle. Acousticallyabsorp-

tive materialswere used to suppressfan noise in inlet and dischargedur_ts

and fan and turbinenoise in the primarynozzle. Figures2(b) and 3(b) show

the CF6-6Dand JTBD-59Awing-enginenacelles,respectively. The production

nacellefor the CF6-6Dand JTgD-59Auses acousticallyabsorptivematerialsto

suppressfan noise in the inlet and fan dischargeducts. The primarynozzle

of the JTgD-59Ais treatedto suppressturbinenoise.

3.2 PROCEDURESFOR SEPARATINGENGINE NOISE SOURCES

In the followinganaly_es,the proceduresare discussedthat were used

to identify,to separate,and to correlatethe engine noise sourcesfrom static

and flyovernoise levels. In order to use the noise-sourceseparationpro-

cedure_for staticand flyovernoise, the flyovernoise data were corrected

to a polar-arcradiusof 45.7 meters,to be consistentwith the measured- '

staticenginedata. The steps used in the correctionprocedureare as

follows: _

; I. Adjustmeasuredflyovernoise to referenceweatherconditionsusing

reference22 and layeredatmospherecorrections(sound-pathweatherat I00 ft.

intervals).

2. Determinethe acousticrange and the directivityangle from the lead

engine inlet centerlineat each point in the flyover-f_'_ht-pathprofile.

: 3. Convertthe flyoverSPLs to 45.7m-polarnoise levelsby using

sphericaldivergenceand atmosphericabsorptionderivedin reference22.

6

! i i

O0000001-TSAIO

4. Estlmat_sof airplaneno_propulsivenois_ IBVQIsat a 45.7 n_etBrradius

( derivedfr_ mQasur_m_ntsof _h_ DC_IO idle flyovernois_, d_cribed in rnfr_r_nc_

23, wore subtractedan an energybasis f'ronsLh_ flyoverdata,

The nolse-sourCodefinitionhad to accountfor the separatecontributions_f

,. discrete-frequencyand broadbandnoise from fan, compressor,Qnd turbln_staq_G,

as well as the broadbandlow-frequencynoise duo to the combustionproc_r,sand

" to externallygeneratedjet nolso. In addition,It was ruquiredthat the s_llul

, the separatedstaticand flyovernoise sourcesbe equivalenttu the measured

levels,

#

3.2.1 Separationof Low-FrequencyNoise ComponentsfromMeasuredData

" In order to eliminatethe maskingeffectsdue to groundreflections,static-

and flyover-noisedata measuredwith flush-mountedmicrophoneswere used to

identifyand to separatethe low-frequencynoise componentsfrom the measured

data. By using the proceduresoutlinedabove,the flyovernoise data were

projectedback to a polar-arcradiusconsistentwith the static-enginenoise data,

No correctionswere made for the effect el_ Jet-noisesourcedistribution,since

the adJusi_entswould not have been applicableto flyoverand staticdata at jet

velocitiesless than takeoffvelocity,where core noise becomesmore prominent, _i

The low-frequency(50 to 1000 Hz) parts of the measuredstaticand flyover ]

adjustedspectrawere assumedto be due to contributionsfrom jet-plus-cor_ :]

noise. The high-frequency(1250to 10,000Hz) parts of the jet-plus-corespectra _were determinedby using an assumed"roll-olaf''rate based on inspectionof measured

- , data at each inlet angle (see fig. 4). Roll-offrateswere found to vary from

4 to 6 per octave,dependingon the inlet angle (table3). The remaininghigh-

frequencyportionof the measuredspectrawas asstmledto be due to turbomachinery-

noise components.

3.2.2 Comparisonsof Staticand FlightLow-FrequencyNoise

Figure5 presentsa typicalcomparisonof flightand static low-frequency=

. noise OASPLs for the Dc-g-30/JT8D-109measuredat a primaryjet velocityof

221 m/sec. The figureshows littleor no differencebetweenstaticand flight

_ OASPLs in the inlet quadrant. In the exhaustquadrant,the flirlhtlevelsare:= ,

?,

,I I I i | i! ........*.,=. ,......... ,L _l . .- I ...........

00000001-TSA11

( IQw_r than th_ static lev_Is, Comparisonof _taticand flight_pectraat an

inlet an(]1_Qf 50° (fl,q,6) .showsn_arlyaqual p_ak SPL_ in the 315. to 1260-Hx

frequDncyrange,which are re_pon,_iblnfor thQ equal ,staticand flightOASPL_

iw_thn Inl_tquadrantof fl_ure 5, At a primaryJot velocityof 3q_ m/_oc

(fi,c_,l), thQ flightlowofraqu_ncyOASPL,sare lev_r than thQ _tatlcOASPL_at 4,

a11 an(jlo_,wlth tho lar,q_,_treductionsin the exhaustquadrant,

Figure8 shows a comparisonof flightand staticlow-frequencyOASPLs for

the DC-IO-40/JTgD-SgAat a typicalapproachpower setting(primaryjet

velocityof 26B m/see). The flightlevelsare higherfor inletangles up to

120_. Comparisonsof staticand flightspectraat an inletangle of 50° in

figure9 show flightSPLs higherthan staticSPLs, in contrastto the relative

levelsfor the DC-g-30/JTBD-I09(fig. 6), Another'low-frequencynoise source

relatedto the impingementof the fan-jetexhauston the deflectedflaps under

approachflightconditionis thoughtto be responsiblefor the higherflight

noise levels in the inlet angles in figureg, At a higherjet velocity

(436m/sec)correspondingto takeoffpower (fig.lO),,theflightlow-frequency

OASPLsare lower than the staticOASPLs at all angles That trend is similar• I

to the trend observedin the Dc-g-30/JTBD-I09at takeoffpower. All of the

comparisonsindicatethe need to identifyand to separatethe jet and core

noise componentsfrom the measuredlow-frequencynoise,

3.2.3 Separationof StaticJet- and Core-NoiseComponents

The first step is to identifythe individualjet and core noise spectral

componentsfrom the measuredlow-frequencySPL spectra. The assumptionsused

are summarizedbelow and are illustratedin figure11.

I. At high power settings(jet velocitiesabove 305 m/sec),the

measuredjet-plu_-corenoise spectraare dominatedby jet noise.

?. At low power settings(jet velocitiesbelow 200 m/sec)_core

noise dominates.

3. At intermediatepower settings,the contributionsof jet and of

core noise are about equal.

E

; 8

t "........ ' 00000001-TSA12

_._, In g_tneral, pure-jet-noise spectra nannall._ed in term._ Qf 1/3_Qctave-band _PL_

_. r_latlveto OASPL_have been showh to correlatewith the nondimnnslonal5trouhal

parameter, fD/Vjp. An _xamp1_of thQ correlationi_ _hown in figure12 for,: model-scale_tatlcJet noi,_ at 120" from the inlet. In _ontra_t,cor_ hollo,

which is of hlilherfrequency,do(_ not correlatewith Str'ouhalnumber. It ha';L'

_" boon _hewn in reference_4 that for a glvon engine th(_peak frequencyand the

_i7 normalizedspectral_hapo ar_ independentof power sottln,q_(l.o.,prlmary-Jot. velocities). Plottingthe static JT_ID=i09low-frequencynolso _poctraversus

:_ Strouhalnumber (o.g.,flu. 13) shows the data for hiflhoj_t=volocitycollapsed ""

: , to a sli_glespectr_nIdontlcalto the mOdel-scalejet noise spo_truiiI-utthe _ame

ii_ angle. The data for lower Jet velocitieshave shiftedprogressivelytu hiohor

!i Strouhalnumbers;that is, they do net correlatewith Strouhaln_b(Jrs. The!;

_:" peak frequenciesof those spectraare approximately400 to 500 Hz over a wide

_._i: range of jet velocitiesand angles (fig. 14). The low-frequencynoise spectra

'" for the very low jet velocitieswere no_lallzedas functionsof the peak

_ frequencyand SPL, which was suggestedin reference24. The resultingspectra

are shown in figure15 for inlet anglesof 50°_ 90°, I70_, and 140°. _Fhe

,_ spectraare the same i_orall angles,and they are thereforeconsideredto be

individualcore-noisespectra.

;.: The correspondingnormalizedspectrafor jet and core noise identifiedfrom the staticJTgD-SgAlow-frequencySPL spectraare shown in figures16

L and 17 for angles50°, 90°, 120°, and 140°. Again, the normalizedspectral

shapesfor core noise are the same for all angles,and they are nearly

, identicalto the spectralshapesderivedfor the staticJTSD-I09core-noise

component. The core-noisepeak freq=_ncies(fig.IB) for the static

, JTgD-SgAengineare lower than the correspondingcore frequenciesfor the

JTBD-IO9engine.

With the jet- and core-spectrumshapesthat had been determined,the

secondstep in the analyseswas to determinethe relativelevelsof jet and

core noise in the measuredlow-frequencyspectra. A curw-fit techniqu_w_s

requiredto providethe best combinationof the jet and core normalized

spectrato fit the measureddata as illustratedin figure19. Initialesti-

_. mates of the individualjet and core noise SPLswere combinedto give an

.................. II I_ _ ,-. , , ,, ,, d

00000001-TSA13

o_tlmatedj_t_p1_._-cQr_nQlse SPL _p_ctrum, Beglnnlnqwi1:hthe I/3,._Qctave_-

band center frequencyat rioHz and cont,lnuln_.}to _ucce._,_Iv_bands at hl._her

fr_qu_ncle,_,th_ _f_tlmat__dSPL_ w_r_ _ubtra_t_dfrom the mOa_ur_dSPL_, _Ivlng

the _um of the dlffnrence_betweenthe measuredand th_ o_tlmatedSPL _poctra

i_, for thO ?-4frequencybands as" _4

, ,, _ , [SPL(1) .-SPL(1) ]2" ---- measured e:,tImated_. t'1 .,,

L' The quantity 2 (variance)is used to find out how close the estln_tedSPL '

i_,:. spectrumis to the actualspectrum. The estimatesof individualJet and corO

i noise level_were then incrementedindependentlyto cr(_atea matrixof

i, _,2-values.Curve-flttechniqueswere then used to determinethe set of Jet

_i and core levelstllatwould give the bes'_fit to the measuredSPL data. The

!" OASPLs for the individualJet and core componentswere then calculated,,;

The measuredlow-frequencyOASPLs and Jet and core OASPL_ e_Ived by

_ thatmethod are shown in figure20 for the JTBD-IO9and in figure21 for the

ii JT9D-_gAstaticdata at 120°. For simplicity,both jet and core OASPLsare

!" correlatedon the basis of the primaryjet velocity. In the JT8D-IO9,the

:. measuredlow-frequencynoise levelsare dominatedby core noise at jet

_, velocitiesbelow 192 m/see and by jet noise at jet velocitiesabove 340 m/sec.

Similarly,the total low-frequencynoise levelsfor the JTgD-59Aare dominated

by core noise at jet velocitiesbelow 120 m/sec and by jet noise at jet vole-

!,: citiesabove 240 m/sec, Tables 4 and 5 presentcorrelationsof staticjet- '

i._ and core-noiselevelsfor the JTBD-IO9and the JTgD-59A,respectively,for

angles from 50° to 150°,

3,2.4 Separationof FlightJet- and Core-NoiseComponents

The procedurespreviouslydescribedfor the separationof staticjet-

and core-noisecomponentswere used to identifyand to separatethe individual

ii spectraand levelsof jet- and core-noisecomponentsfor the DC-9-30/JTBD-109

and the DC-IO-40/JTgD-SgAflyovernoise data. The normalizedjet-noise-

componentspectraderivedfrom the DC-9-30/JTBD-IO9flyoverdata are presented

in figure 22 for angles of 50°, 90°, and 120". The relativejet velocity,

' 10

4,_ .... I_ , ,, I _ ..... , ..... , " I I II

00000001-TSA14

I I I I l I ) L I

Vjp - Va, was used in the Strouhalparameterinsteadof the primaryjet

velocity,Vjp. The correspondingin-flightspectrafor the DC-IO-40/JTBD-59Aare presentedin figure23. The normalizedspectralshapesfor core-noise

componentsfor the DC-B-30/JTBD-I09are presentedin figure24. The core

spectralshapeswere identicalfor all angles. The in-fllghtcore peak

frequencies,fpeak"were higher than the peak frequenciesobservedstatically(fig.25). The correspondinqnormalizedspectralshapesfor core noise of

_ th_ DC-IO-40/JTgD-5gAare _hown In figure26. The core peak frequenciesa

of the JTgD-59Awere also higherin flight (fig.27). -'--

Examplesof correlationsof the individuallevelsof jet- and core-noise

componentsand the combinedlevel for the twc componentsare given in figures

28 and 29 for the DC-9-30/JT8D-I09and the DC-IO-40/JTgD-59Aflyoverdata at

120°, respectively. For the purposeof comparison,the individuallevelsand

the combinedtotal levelswere correlatedon the basis of primary-jetvelocity.

-_ 3.2.5 Separationof TurbomachineryNoise from Static-EngineData

In.the inlet quadrant,high-frequencynoise consistsprimarilyof fan-

inlet noise;in the exhaustquadrantit consistsprimarilyof fan discharge

< and turbinenoise. Fan noise is composedof discretetones at blade-passing

• frequencyand of harmonicsat multiplesof the blade-passingfrequencysuper-

- imposedon a broadband-noisespectrum. At supersonicfan tip speedsmultiple-

i: pure-tone(MPi)noise is generatedby the fan rotor and is propagatedout the

_: inlet. Turbinenoise is composedof discretetones and a broadbandnoise

7/ spectrumgeneratedby the stagesof the low-pressureturbine. For the spectral

-=_i comparisonsthat follow,tones generatedby the fan rotor and by the booster

stage are designatedby F and B, respectively,and the numbersl through5.

=_' Fundamentaltones generatedby the last threestagesof the low-pressureturbine

_-i: _tagesare designatedby T and by the numt_.rs2, 3, and 4 for the JT8D-I09,

=_ by 3, 4, and 5 for the CF6-6D,and by 4, 5, and 6 for the jT9D-59Aengines. The

-; followingsectionsdiscussthe component-noiseseparationbased on static-engine• .,C

_:_," data for the refannedJT8D-I09. Similarresultswere obtainedfor the CF6-6D

_i.: and the JT9D-59A.E.,

11

I I m" ( ' I_, i&I I# ' _ "" , ' ' IT .... |

00000001-TSB01

I I I [ ! ! I

! 3.2,5.1 Removalof low-frequenF_noise from measureddata. - Before turbo-

machinerynoise sourcescould be separatedinto components,_low-frequency

noise sources(jet-plus-corenoise)were removedfrom the measureddata.

Correlationsof Jet and core noise described_n section3.2.1 were used to

define the jet-plus-core-noisespectraand levels. Table 3 presentsthe

roll-offrates used-to-extrapolatethe low_frequencyjet-plus-corenoise to

the high frequencies. Beginningwith the 10 kHz band and continuingto

successivelylower bands,the jet-plus-corenoise levelswere Subtractedon

£' an energy basis from the total measuredlevel.sto get the total turbomachinery

noise levelS. The subtractionprocedurecontinue&band by band until the

jet plus-core-noisespectrumwas_withinl dB of the totalmeasureddata. The

high-frequencyturbomachinerynoise was then extrapolatedto lower frequencies

_ (fig.30) by using roll-offrates consistentwith fan/compreSsortest-stand

data previouslyobtainedfrom enginemanufacturers(table3)..i// -

3.2.5.2 Separationof data into discretetones and broadbandnolse.- The

:_ proceduresfor predictingturbomachinerynoise requiredthe determinationof

_ the relativecontributionsof tones and broadbandnoise to a given spectrum.

_: The followingcriteriafor separatingbroadbandand discretetone noise were

._:. used:

_iiII I. The tones consideredwere those of the fan-blade-passingfrequency

_': (BPF),the secondthroughthe fifth harmonics,fan booster(BPFof the

. first stage of the low-press_recompressor),and the BPF tones from the

last three low-pressureturbinestages.

2. If more than one tone from the same noise source (e.g.,turbine

BPFs) occurredin the same I/3-octaveband, they were assumedto have equal

! strength.

3. If more than one tone from differentsources (e.g.,one or more

turbineBPFs and a fan harmonic)occurredin the same I/3-octaveband, narrow-

band data were used to determinethe relativelevels. Detailsof the pro-

cedurewill be describedin more detail in section3.2.5.4.

4. The broadbandboise spectrumwas assumedto be piecewiselinear

with I/3-oct_ve-bandnumber. The broadbandlevel in the band containing

• the BPF tone was determin6dby interpolatingbetweenadjacentfrequencybands

12

" i' I , II ............

00000001-TSB02

, i | l

ti, i

_ composedof essentially broadband noise only.

;,.. The sound pressure level (SPL) of the tone(s) in a band was obtained byI'

subtractingthe mean-squarebroadbandpressurefrom the totalmean-square1

_: tUrbomachinerysound pressure The total mean-squaresound pressureof the

_;_' tone(S)was then distPibutedequallyamong the tones presentin the band for

! the same seurce and finallyconvertedto a sound pressurelevel

;_ 3.2.5.3 Separationof inlet and aft turbomachinerynoise• - In..orderto

separateinlet from aft turbomachinerynoise levels,proceduresdeveloped

_ under the NASARefa_ Program(ref. 21) were used to definethe directivityof

,;,_:. the exhaustnoise in the inlet quadrantand that of the inlet noise in the aft

!: quadrant. Table 3 presentsthe roll-offrates for all-frequenciesdetermined

I_i for the contributionof inlet and aft levelsin their oppos,ngnoise quadrants.

Ill 31.illustratesthe resultsof the to theFigure separationprocedureas applied

JT8D-I09. Similarresultswere obtainedfor the CF6-6Dand JTgD-5gAstatic-noise

levels.

i 3.Z.5.4 Separationof fan-exhaustand turbinenoise. - At power settings, below takeoff,noise generatedby the last three stagesof the low-pressure

turbinecould in most cases be identifiedfrom narrowbanddata. Figure32

shows the prominentfeaturesof JT8D-I09and OT9D-59Aturbinenoise as tones

with a haystackingof broadbandnoise around the blade-passingfrequencies

_: of the low-pressureturbinestages. For those power settings,narrowbanddata

_i. were used to separatethe peak turbine(broadbandplus discrete)from the fan

_; I/3-octave-bandlevels for a given fan rotor speed and angle as given in figure

, 33. That procedurewas used to define turbinelevelsfor a wide range of angles

i,'_ at each fan rotor speed at which turbinenoisu could be identified. The turbine

direci_ivityderivedfrom the source-separationanalyseswas found to be approxi-

,_ mately constantwith power setting. It is given in figure34, togetherwith

similarresultsderivedin references25, 26, and 27 and in a Douglasanalysis

of the JTgLI-ZUdata. In addition,the turbinebroadband-spectrumshape was found

to be approximatelyconstantwith power settingand angle, as is shown b_ the

solid line in figure35, The derivedspectrumshape compareswell with th_

; resultsof reference25 and Douglasanalysisof the JTgD-20data, but reference

_ 26 shows a more broad spectrumshape at frequenciesbelow the peak frequency.

13

00000001-TSB03

! I I, : I I I I !, I

Those procedureswere Used to define turbinenoise spectra,levels,and

directivities.With the spectradefined,the turbinenoise levelscould be

subtractedfrom the total-aft-turbomacllineryspectrallevelson an energybasis

to obtain the fan-exhaustnoise levelsshown In figure 36 for the JTBD-IOg

static-noiselevels. Aoaln, similarresultswere obtainedfor the CF6-6Dand

the JTgD-5gAengines. The spectrallevelswere then normalizedwith respect

to engine airflowrates and correlatedwith physlcal-and corrected-fanrotor

speed and angle. _.

3.2.6 Separationof TurbomachineryNoise from Flyover-NoiseData

To providea canparativeflight data base, the high-frequencylewis

were correctedto a 45.7-meterradiusand separatedfrom the measured flyover-

noise levelsby a proceduresimilarto that used in the static-noiSeanalysis.

Before the turbomachinerycomponentscould be identifiedand separatedthe

high-frequencynoise levelshad to be correctedback to the sourcefor the

effectsof Dopplerfrequencyshift on the broadbandand the discrete-tonecom-

ponents. In addition,all spectrawere inspectedfor completeness,or for

data dropouts. Data dropoutsgenerallyoccurredat the very high frequencies

when the airplanewas at such large distancesi_romthe microphonethat the sound

generatedwas not distinguishablefrom the backgroundnoise. In those cases,

extrapolatedvalueswere supplied. Once the correctionswere applied,the

flyoverspectrumwas then separatedinto the jet plus core, inlet turbomachinery, !

and aft turbomachinerynoise components(figs.37 and 38) as describedpreviouslyin section3.2.5 for staticnoise data. To deriveturbinenoise levelsin the

flightdata, the derivedstaticlevelswere modifiedto accountfor the effects

of jet exhaustsound scattering(describedin section3.4.l.4). The modified

turbinelevelswere then subtractedfrom the aft turbomachinerylevelsto yield

the fan-exhaustnoise levels (fig. 39). As with the static-turbomachinery

source levels,the separatedsource levelswere normalizedwith respectto air-

flow rates and correlatedwith physical-and corrected-fanrotor speed and

angle.

14

i

00000001-TSB04

3.3 DEFIN/TIONOF STATIC-TO-FLIGHTDIFFERENCES

To identifythe effectsof forwardmotion on the enginenoise sources,

the static-engineand the flyovernoise levelswere comparedand the areas of

disagreementdiscussedin terms of the mechanismsthat alter the generation

and the propagationof the _ise under forwardmotion. To comparethe static-

engine and the flyovernoi_e data, the separatednoise sourcesthat had been

determinedwere projectedto flight conditions,with the same adjustments ...t

appliedto the f_yovernoise data (section3,2). Flyoverand static-projected

noise cOmponentswere added, to give the originalf.Lightle_e.lsand the total,p

static-projectedlevels. In the followinganalysis,comparisonsof flyover

and statlc-projectednoise leve1_are presentedand the areas of disagreement

are noted.

3.3.1 det and Core Noise

Comparisonsof staticand flighttotal low-frequencynoise were presented

in figures5 - I0. In general,the flightlevelswere shown to be lower than

thosemeasured duringstaticoperationat all angles. For low jet velocities

comparisonsof DC-g flyoverand JTSD-IOgstaticdata show that the flightdata

are only slightlyless than the static levels,whereas,the DC-IO flyover

levelsare slightlyhigher than the JTgD-59Astaticlevels in the inlet quad-

rant. Separationof the total measureddata into its jet and core noise

. components(figs.20 and 21) have shown that core noise is the dominantsource

at low jet velocitieswhile the jet noise dominate_at hightjet velocities.

3.3.2 TurbomachlneryNoise

Figuv'e40 shows comparisonof flight-aridstatic-projectedtone-corrected

perceivednoise _evels(PNLT)plottedversus inlet angle for the DC-9-30/jTBD-IOg

airplaneconfiguration.At approachpower (fig.4a), the flightdata are lower

" than the staticdata in both the inletquadrantahd, to a lesserdegree,in the

exhaustquadrant. Conversely,for a takeoffpower setting(fig. 40b), the

flightdata are higherthan the static. Figure41 shows comparisonsof the

flight-and the static-projectedI/3-octave-bandspectraat approachpower, at

i_ particularanglesof interestin the f11ght-pathprofile. The higher static

T'

:_' 15)

i iI ,e ( .........................-........._].....................l _ " 'L_;................... ,............ 4_ ;.......................L. ....... J ......... " ........

O0000001-TSB05

yl I I , I I I I!,i

_: PNLTs are due to increasesin the high frequenciesat and above the fan blade-

!_ passingfrequency. The differencesare less pronouncedat aft angles, At

i takeoffpower,measured flyoverand staticspectraare dominatedby low-frequencyi: Jet noisesources.There is little contributionfrom turbomachinerynoise.

),_ Figure42 shows comparisonsof flyoverand predictedPNLTs for the

_,. DC-IO-IO/CF6-6Dairplaneconfiguration.The statlc-p_edictedlevelsare again

higher than the flightin the inletquadrantat approachpower (fig.42a), but ,.

the flightlevels are higher than the static levelsat the peak aft-noise

angles. Figure42b shows that at takeoffpower the flightdata are higherthan

the staticat the peak inlet-noiseangles and that the staticdata are higher

than the flightat the peak exhaustangles. Figures43 and 44 show the flight-

and the static-spectracomparisonsfor approachand for takeoffpower settings,

respectively. Figure43 shows that the increasedstaticPNLT.sat approachpower

i" a_e due to increasedlevelsat the fan fundamentalfrequencyand the frequencies_ of the fan harmonicsand turbineblade passing. For aft quadrantangles,the

level of the staticfan fundemientalis higher than ififlight,and the increased

flight levelsare due to higher levelsat the turbineblade-passlngfrequencies.

Figure44 shows that increasedflightlevelsin the inlet quadrantat takeoff

power settingare due to the propagationof multlple-pure-tonenoise (MPT)at

multiple frequenciesof the fan speed. ]_naddition,the high-frequencystatic

data at the fan fundamentaland harmonicsare higherthan the flightdata, the

-_ differencesbecominggreaterwith increasingfrequency.r

Figure45 shows staticand flyoverPNLT comparisonsfor the DC-IO-40/

JTgD-59A. As with the DC-IO-IO/CF6-6D,the staticdata for approachpowerare

higher in the inlet quadrantand lower in the aft quadrantthan the flight

data. But at takeoffpower the staticdata are higherthan the flightat all

angles in the flyover-noisehistory. Spectralcomparisonsat approachpower

(fig.46) show that the increasedstaticlevels in the inlet are due to the

higherlevelsof the fan fundamentaland harmonics. At angles fartheraft,

the flightdata are higherfor frequenciesat and near the I/3-octaveband

containingthe turbinediscretetones. At takeoffpower (fig.47), the

spectraare dominatedto a large extent by jet noise,but the contribution

of turbomachinerynoise is still evident.

16

I

00000001-TSB06

I 3.4 CORRECTIONSFOR THE EFFECTSOF ENGINEINSTALLATIONAND ATMOSPHERICPROPAGATION

To identifythe effectsof forwardmotion on enginenoise sources,it is

necessaryto adjust the static-enginedata for engine installationand propa-

gation effects. The effectsof engineinstallationinclude(I) effectsof

relativeengine location(axialseparationbetweenengines),(2) effectsof

fuselageand wing shieldingof the fan-inletnoise, (3) effectsof sound

scatteringof fan and turbinenoise by the wing-flap-wheelwake, (4) effects

of jet-exhaustsound scatteringof turbinenoise,and (5) effectsof inlet

contouron fan-inletnoise. Nonpropulsivenoise,which is describedin

reference23 and which is definedas the noise generatedin flightby sources

other than the engines(fuselage,wing-flapsystem,landing-gearstruts,

and wheel wells),must also be includedin the categoryof installation

effects. The effectsof wing shielding_nd of sound scatteringby the wing-

flap-wheelwake will be discussedfor the DC-9-30/jTgD-I09airplanecon-

figuration,and the effectsof jet-exhaustsound scatteringwill be discussed

for the exhaust-nozzleconfigurationfor the CF6-6Dand for JTgD-59Ahigh-

bypass-ratioengines.Propagationeffects,in particular,the effectsof

excessattenuation,will be discussedfor both a DC-9 and a DC-IO airplanein

section3.4.2.

3.4.1 Engine-lnstallationEffects

3.4.1.I Enginelocation.- Figure48 shows the locationof the engineson the

DC-lO-lO. Two enginesare mountedunder the wings, and a third is mounted in

the verticaltail 68 feet aft of the wing engines. For low-altitudeflyovers,

the engine noise cannot be consideredto come from a point source,with three

enginesat the same axial location. Static levelsfor each enginemust there-

fore be adjustedfor sphericaldivergence,atmosphericabsorption,Doppler

shift,etc., as functionsof the source-pathangle (anglebetweenthe observer

and the flightpath),the directivityangle (theangle betweenthe observer

and the inlet centerline),and the acousticrange relativeto the ground

microphone.

11

00000001-TSB07

l I I i I I I !' I

• Figure 4g shows the effect of th_ DC-IO-IO tail-englne locatlon on

directivlty anglos during a lev_l-fiight flyover at an altitude of 152.4 m,iF When the airplaneis directlyoverhead,the propagationangle from the inlet

i of the wing-mountedenginesis approximately10" greaterthan that of the tail

engine. As the airplaneapproachesand passesoverhead,the differencesin

directivityangle and in acousticrange make the noise levelslower than they

would be if the engineshad no axial separation. The effect is the opposite

for the noise levels in the aft quadrant. The effectsof Dopplershiftand,

to a lesserdegree,of atmosphericabsorptionwill also be affected. "_

3.4.1.2 Fuselageshieldin9. - With the third DC-IO enginemountedabove the

fuselagein the verticaltail, fan-inletnoise is shieldedby the fuselage

from microphoneslocateddirectlybeneaththe flight path,which further

reducesthe inlet flyover-noiselevelsfrom those of the staticcase.

3.4.1.3 Wing shieldingand wake sound scattering.- Comparisonsof static

and flightnarrowbandspectra (ref.14), which were measuredby microphones

mountedin the inlet of the JTSD-lOg-poweredDC-9-30airplane,showedthat the

levelsof the randombroadbandnoise and tones at discretefrequenciesdid not

changesignificantlyin flightat approachpower settings. Similartrends

were observedfor staticand flight narrowbandspectrameasuredin the fan

duct and in the tailplpe,which suggestedthat the static-to-flightdiffer-

ences observedin figure40 were due to factorsaffectingthe propagation

ratherthan the generationof fan noise. Specifically,it was suggestedthat

the locationof the fuselage-mountedenginesrelativeto the wing affectedthe

propagationof fan noise. Figure 50 shows the locationof the JT8D-I09engine

relativeto the wing-flapconfigurationof the DC-9-30airplane. Fan-inlet

noise propagatingat shallowangles is shieldedfrom microphonesunder the

flightpath by the wing-flapsystem. In addition,fan-inlet,fan-exhaust,and

turbinenoisemust propagatethroughthe turbulentwake from the wing-flap-

landing-gearsystemduring forwardmotion. A detaileddescriptionof the

analysesperformedto accountfor those effectsit reportedin reference21.

The approachused to predic_the attenuationdue to wing shieldingwas adapted

i from the barriertheorydescribedby Beranekin reference28. The barrierL

, theory,which is based on optical-diffraction(Fresnel)theory,assumedthat

18

E._. ............................................-............................................................_ ...................................................................................................... _ ........................

00000001-TSB08

'I ] _ t 1 I I I I to"

t only t_,eincld_ntwav_fieldclose to the top edge of the barriercontributed

! 4 to the wavefielddiffractedover the barri_r. The barrl_rwa_ modeledby th(_

il wing-flapsystem,and the noise generatedby th_ fan was assumedto com_ from

a point source,

To accountfor the dlffer_ncesbetweenstatic-projectedand flyovernoi_(_

data in the regionsoutsidethe shadowzone, it was _uqgestedthat the wake

generatedby the wings, flaps,and landinggear alteredthe propagationel

: turbomachinerynoise sources, An analysiswas thereforeperformedby applyinq

Rudd'sconceptof sound scatteringby turbulence(ref.29). Rudd's treatment

of the scatteringof sound by turbulentjets was modifiedto representthe

i_ similarspreadingrates and velocitydistributionsof the wing-flap-wheel

'.'

wake.

i., 3.4.1.4 Jet-exhaustsound scattering.- Figure51 comparesthe furbine-noise

suppressionduring staticand flyoveroperationmeasuredwith and withoutthe

acousticallytreatedturbinereverserinstalledin the CF6-6D. It shows that

more noise reductionwas measured in flight than in staticoperation. On the

basis of Rudd'sresultsand an experimentalprogramdescribedin reference30,

which was conductedto investigateshieldingand scatteringby a jet flow, it

was shown that the thicknessof the jet was very effectivein reducingaft-

radiatednoise. Comparisonof the differencein the fan/ambientshear layer

betweens.taticand flight operationof the CF6-6D in figure 52 suggestedthat

the increasedlevel of turbinenoise in flightis primarilydue to the de-

:. creasedsound scatteringthroughthe fan ambientshear layer to the far field

during forwardmotion. To investigatethose effects,the sound-scattering

theoryof Rudd was appliedto the CF6-6Dand JTgD-59Aturbine-staticnoise

'., levels. The thicknessof the JT8D-I09shear layer was estimatedto be

_" smallerdue to the longduct nozzleconfiguration. As a result,the effects

i of sound scatteringon JTSD-I09turbinenoise were consideredto be negligible.

It shouldbe noted that becausejet-exhaustsound scatteringaffectsthe

' relativelevelsof turbineand fan noise in the same I/3-octave-bands,the

source-separationprocedureshad to be modified. The separationof fan ex-

haust and turbinenoise from flyovernoise data, which was based on the

19

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00000001-TSB09

I I I I I , I

relatiw turbinenoise 1_velsdetermlnBdfrom staticnarrowbanddata, wa_

' modifiedto Increasethe turbinenoise levelsrelativ_to th_ fan I_wI_ in

accordancnwith the decreasedscatteringeffect throughthe fan ambientshear

layer (_ectien3,2,6),

3.4.1,5 Inletcontour. Figure 53 compare_the Inlet _adrant spectrafor a

flight inletwith that of a bellmouthinletdurin9 staticoperationof the

JTgD-20at statictakeoffpower. The noise levelswith the bellmouthinlet

are higher,partlcularlyin the inlet quadrant. Potential-flowstudiesshow

thatwith the productionnacelleoperatedstaticallythe ambientair is drawn

in fronla11 directionsas in a classical"sink"flow with a stagnationpoint

on the nacellelip, as in figure 54. The result is that the flow accelerates

around the lip, producingregionsof highMach numberson the inletwalls.

Duringforwardmotion,flow is ingestedalong lines nearlyparallelto the

inlet centerline. As a result,the inlet stagnationpoint moves insidethe

nacellelip (fig. 55), and the high-velocityflow regionsare reduced.

That phenomenonis most importantin the attenuationof multiple-pure-

tone (MPT)noise generatedby shock waves from the rotorsoperatingat sonic

and supersonictip speeds. In staticoperation,MPT noise propagatingin the

nacellesufferssignificantattenuationin traversingthe highMach number

regions. Duringforwardmotion,MPT noise propagatesout of the inletwith-

out appreciableattenuation. BecauseMPTs occur at frequenciesthat are in-

tegralmultiplesof the fan shaft speed, the increasednoise levelsin flight

can occur at any point in the spectrum,althoughthey occur typicallyin the

low to middle frequencies. In addition,the increasedflows during static

operationare typicallyhigher than the optimumflow for the designacoustic-

: liner impedance,which can affectthe attenuationof the propagateddiscrete

tones at the fundamentaland the harmonicsof blade-passingfrequency.

3.4.1.6 Nonpropulsivenoise. - The noise generatedby the airframein fliqht

providesa noise floor from which potentialengine-noisereductionsmust be

evaluated. At lower fan speedsand with more effectiveacousticlinersin

fan nacellesand dischargeducts,nonpropulsivenoise becomesdominant in

: flight. Figure 56 illustratesthe variousnonpropulsivenoise sourceson a

20

' tO0000001-TSBIO

l

1 ', i ! , i L I ! I ..........

DC-I(]airplaneconfiguration, Fluctuatlnfllift forcoGQn th_ wln_flap sy._tom,

fuselag(_,emp_nnago,and opon wh_l w_11_ durlnq approachr_ult in a iift_-

dipole sourceof noise, Drag dlpole_are qon_ratedby fluctuatlnqdri_qfQrc(;F,

on tho_e componentsand Qn th(_.landingogear_tructurn._,Thu proc(_dur_._,_vv.,d

for definingnonpropulsivenoise sourc(:._are r_.,viewedin rofer_nc(;?-3,

3,4,2 PropagationEffects: ExcessAttenuation

Comparisonof flyovernoise and static-enginenoise projectedto fli_lht --

conditionshas consistentlyshown static-projectedspectrahigherthan flight

spectraat frequenciesgreaterthan blade passage(refs,6, l, 9, ll). Since

the high-frequencyreductionwas independentof engine type and observation

angle and since no reductionwas indicatedby microphonemeasurementsin inlet

and fan ducts, it is believedto be due to increasedatmosphericattenuation

over propagationdistancesusuallyldrgerthan those for stati¢measur_ents.

Specifically,it is thoughtthat the high-frequencyspectraldifferencesare

, due to excessattenuation,which is defined in reference31 as the attenuation

. over and above the attenuationobtainedby using currentproceduresto predict

molecula_and classicalabsorption, (ref. 22).

3.4.2.1 Descriptionof problem.- Comparisonof CF6-6Dstatic-engineI/3-

octave-bandspectraprojectedto flightconditionsand DC-IO-IOflyover-noise

data (fig. 57) showedthat at frequenciesgreaterthan blade passagethe

staticspectrawere higherthan the flight spectra. At the 8OO0-Hzband,

'= differencesof from lO to 20 dB were common. Observationof narrow-band

spectrameasuredby microphonesmounted internallyin inlet and fan discharge

ducts of the CF6-6Dduringstaticand flightoperationshowedchangesin the

high-frequencyregionof the spectraof the order of 2 dB (fig.58). That

result indicatedthat staticand flighthigh-frequencysound sourceswere

•_ substantiallythe same. In order to evaluateand to eliminate,if possible,

:_ the procedureused for correctingtest-dayspectrato referenceweather

conditionsas a potentialsourceof the high-frequencyerror,DC-IO-IOflyover

. noise spectrameasuredduringapproachat an altitudeof 12l meters for three

: differentweatherconditionswere compared. The sound-pathweatherLondltiotv./

_ for each run are shown in figure 59; the test-dayspectraare shown in fiuure

:' 60. Comparisonsof the spectraand of the weatherconditionsaloft showed)

!_

" O0000001-TSBll

that two of the spectraw_rn nearlyequal and that the weatherconditlQn_

wore _hnilar, How_wr, the highofrequoncyr_glonof tho third spectrumwa_

cOnsidorably|ower than tho_e of the other twQ, which was _imilarto the

resultsin flguro57, A1thQuqhthe temperatureprQfileswere all _Imllar,tho

humidityprofileof the thirdwas considerablyl_w_r,which indicateda hlqher

|evolof atmoBphoricabsorption. Correctinqthe measuredspectrato reference

weatherconditionsby using sound-pathweathercollapsedthe data to apprex'i=

merely the same referencespectrum(fig.61). That result indicatedthat the

use of ARP 866 to correctmeasureddata to a given set of referenceweather ,=.

conditionson a layered-weatherbasis was adequateand that it was not the

cause of the high-frequencydifferencesin figure 57.i.

The high-frequencydifferencesobservedin figur{ 57 thereforeappeared

to be due to increasedatmosphericattenuationover propagationdistances

usuallylargerthan those for static-enginemeasurements- excessattenuation.

The primarycause of excessattenuationwas believedto have been sound

-. scatte,-in9due to atmosphericturbulence. Secondarycauses,such as sound

refractiondue to temperatur_and wind gradientsand to variationsin ground

absorption,were shown to have small effects.

3.4.2.2 Test configurationsand programs.- The data base for the analysis

consistedof measuredflightspectraobtainedfrom the DC-g-30airplane

poweredby JTBD-I09refan engine (fig.I) and from the DC-IO-40airplane

poweredby JTgD-59Aengines (fig.3). For the DC-9-30flyovers,three

microphonelocationswere used,with a maximumtotal spacingof approximately

3,2 km. A summaryof the DC-g-30/JTBD-IO9test data is shown in table 6. For

the DC-lO-40,two microphonelocationswere used, with a maximumtotal spacing

- of approximately2.2 km. A summaryof the DC-IO-40/JTgD-SgAtest data used

is shown in Table 7. The data were recordedduring the followingtypes of

flyovernoise runswith microphonesdirectlybeneaththe flightpath:

I. Approach-altitudeflyoverat a constantglideslope(table6a)

2. Level flight at approachaltitudewith climboutto takeoffaltitude

, at a constantclimb angle (table6b).

3. Takeoff-altitudeflyoverat a constantc]imb angle (tabl;,s6a and 7).

22

i

O0000001-TSB12

In all runs, nol_e data w_r_ m_a_uredwhnn ther_w_ro no temperatureInwr_l_mr,,

and th_ w_.ath_rvariatlon_wm'(_llmlt_dto t_mpflratur(_b(,twn_n7"C and 17_C

and humiditiesb_tweo.n30 and l_ por_on_,

3,4,_,3 Methpdof ana_.y_i_,_ In order t_ accountfer hlqh_froqu(]n_ydlflor(_nc(__,

between._tatic:proJectedlevelsand flyover_noif,e luvel_,_n add1_i(_nal,;_Jurc(:,

of atmospheri_absorptionhad to be Includud,togeti_erwith the cl_,,_Iral

: and the molecularabsorptioncoefficientsdefinedin rL,,fer{mc(__?, lh(_ .,

:_ additionalattenuationis definedas excessattenuation,

; Hlgh-frequencyspectraldifferenceswere analyzedby comparingflyover-

noise data measuredbeneaththe flightpath of a selectedairplaneco.Fi_lura-

°' tion at a given power setting. Each flyover-noisespectrummeasuredat one

_, microphonelocationwas correctedto referenceweathercondition_;by u_ing the

_ sound-pati_weatl_ermeasuredat incrementalheightsabove the _dcrophone, In

- order to correctthe spectrumto a common altitude(definedas the minimum

:" heightover the microphone)and commonflight-pathprofile,reference_P and

_!. sphericaldivergencew_re appliedto the measureddata at each mi_ropl_one

i location(fig. 6_). lhat approachhad two advantages: The airplaneacted as

a constantnoise sourcewith a uniformpatternof noise emissionduringeach

run, and it minimizedthe effectsof changesin weather,in wind speed,and in

wind directionthat might occur betweenruns, Also, comparingflightdata

with flightdata made it unnecessaryto apply any correctionfor the effects

of forwardmotlonand of the engine installationthat would be requiredfor

making valid comparisonsof staticand flightdata. But that approachcould

introduceinto the analysistwo other variablesas potentialsourcesof error -

differencesin ground reflectionand absorptionat differentmicrophonelocations

and use of two differentmicrophones. In order to eliminatethose variables,

data from a DC-9 level flightrun at takeoffpowerwere compared, The data

had been measuredoverheadat two microphonelocationsat nearlyequal

altitudes. Figure63 shows the resultingcomparisonof spectrameasuredat

altitudesof 13B m and 149 m and adjustedto the common altitudeof 131 m.

:_ The spectraare essentiallyequal at all frequencies,which eliminat,._dmicro-

. phone and microphonelocationas possiblesourcesof error in the sub_;,:,quent

analysis,

23

O0000001-TSB13

| Figure 64(a)pre_ent_a _pQctralcomparlGQnof DC-9_30/JTBD.IO9flyowr

: nol_e mea._uredd_rlng on(_approachrun at th_ clo._e_Inaltltude,._of 262 m_t_rsL.r

and 113 lli,-;ter_,A,_wa_ to be expected,the _poctrummeasuredat 262 mct_r_

wa_ lower at All frequenciesthan that m_asuredat 113 m_terT;,bocau,_of

additionalabsorptionand sphericaldivergenceever a greaterdlstanc(._,Thr:

_:, comparisonof the two spectraadjustedto the commonaltltudc,of 121 met(;r_

is shown in figure64(b), Using the presentprojectionmethod_of reference22

and sphericaldivergenceBhouldtheoreticallyllavecollasped the two adjusted

: spectrato a single referencespectrum, However,as is sho_n by figureG4(b), "

the high-frequ(#ncyregionof the spectrumfrom 262 meters is lower,which

indicatesan additionalsourceof atmosphericattenuation The discrepanciesi:,, °

,, in the low-frequencyrangemay be consideredto be due to grounddip and

thereforeneglected,

:_ A comparisonof Dc--g-30/JTBD-IO9spectrameasuredat takeoffpowerand

largedistancesfrom the microphonesis shown in figure65, The same kind of

" comparisonfor the DC-IO-40/JT9D-59Ais shown in figure66, Aithuughthe

resultswere similarto those obtainedfrom comparisonsat approachaltitude,

the high-frequencydifferencesmeasuredat the higher takeoffaltitudeswere

smaller,even thoughthe spectrawere projectedover greaterdistances. The

i!; fact that the high-frequencydifferencesobservedat approachaltitudeswere:, largerthan those observedat takeoffaltitudesindicatedthat excessattenua-_. tion was greatercloser to the surfaceof the earth.;,

;. 3,4.2.4 Variationwith altitude.- It is reportedin references31 through

_i 38 that excessattenuationis greaternear the earth'ssurfacethan at higher

i. altitudes. S_ecifically,it was shown that there was much excessattenuation

below altitudesof approximately250 metersand littleor none above that

, altitude.

In order to investigatethe variationof excessattenuationwith altitude,

spectraldifferencesderivedfrom approachand takeoffflyoverruns of the

Dc-g-30/JTBD-I09were plottedversusdifferencein overheadaltitudefor

l/3-octave-bandfrequenciesgreaterthan I000 Hz. Becauseof contaminatiml

by backgroundnoise, it was not possibleto define spectraldifferencesfor

frequenciesgreaterthan 4000 Hz at takeoff. At approach,therewas some

24

O0000001-TSB14

i I l I,..I I I......I L.............

contaminationat frequenciesgreaterthan 6300 Hz. Figure67 shows the high-,m

frequencyspectraldifferencesfor flyover-noiseruns at approachand takeoff

altitudes. At the loWer approachaltitudes,the spectraldifferencesincreased

rapidlywith distanceand frequency. Since the takeoffspectrawere projected

over greaterdistancesthan the approachspectra,it was to be expectedthat

the increasedeffectof excessattenuationwould appear as largerhigh-frequency

differences. However,the rate of increasefor the highertakeoffaltitudes

was not as great as that for lower approachaltitudes. That resultconfirms

the findingsin references31 through38, which indicatethat excessattenua- ,_

tiOn is more pronouncedat altitudesless than approximately250 meters.

3.4.2.5 Variationwith frequency.- Two equationsfor excessattenuationwere

., derivedin reference31. The first assumesan ideal atmosphere,for which

sound scatteringmay be treatedas a Bragg diffractionphenomenon. The excess-

attenuationcoefficient,:s' is a functionof frequencysquared. The second

assumesa real atmospherefor which, becauseof the nonhomogeneousand non-

isotropicnature of the atmosphere,Bragg diffractionis only an approximation.

The excess-attenuationcoefficientis then a functionof the one-thirdpower I4

of frequency. .I

, 1

_ _n order to investigatethe variationof excessattenuationwith frequency, .- the excess-attenuationcoefficientsper 330 meterswere calculatedas functions

"' of ASPL and AAlt,where ASPL is definedas the differencein sound pressure

_.i level betweenthe measuredand the projectedspectraand AAlt is the distance_i;.,

_i over which the spectrumwas projected. Excess-attenuationcoefficientscal-

/:'" culatedat approachfor the DC-B-30are shown in figure68. In the curve of

_i"_ figure68, excessattenuationis a functionof the 1.3 power of the frequency,

ii,ii which lies betweenfrequencysquaredfor a homogeneousatmosphereand theone-thirdpower of the frequencyfor a nonhomogeneousatmospheredescribed

, in reference31. Figure69 shows excess-attenuationcoefficientsat takeoff

' for the DC-g-30and the DC-IO-40. Becauseof the smallereffectof excess

attenuationat the highertdkeoffaltitudes,the absorptioncoefficients

for takeoffare smaller. An empiricalformulafor excessattenuationat

takeoff.isnot presented,since,becauseof background-noisecontamination,

the spectraldifferencescould not be definedclearlyat frequenciesgreater

than 4000 Hz. The averagesof the excess-attenuationcoefficientsfor approach

25

L " i ' I l _ ',.................._,_:......................_...............:_.........................._......................_'........................|......................I I _........._-_.

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•I. 1 1 I' :, L I I t _, I....................:1

i

and takeoffaltitudesare shown in figures70 and 71, respectively. From

empirical correlations of DC-g-30 and DC-IO-40 flyover noise, the effects

of excessattenuationin the atmospherewere derived. The correlationsshow

significant data scatter in the spectral differences at high feequencies. In

Order to more clearlydefinethe mechanismsof excessattenuationand to

develop more accurate and reliable prediction methods more work is required.

:= In order to reducethe scatter,data would have to hav_been recordedunder

strictly controlled condit$ons. To obtain• the necessary conditions in an

actualatmosphericenvironmentwould ha_e_beemvery difficult,if not impossible,

_ since tilepropertiesand the conditionsof the air (temperature,humidity, 1velocity,turbulence,composition,etc.) in the atmospherevacy constantlyin ...,r

time and space.

i .

:},

i}'

i?;"

i

I!

• t t 26

00000001-TSC02

! I I I' :'.I l I l i' I

i; 4. DISCUSSIONOF RESUL_S-

4.1 EFFECTSOF FORWARDMOTIONAND OF ENGINE INSTALLATIONON JET- AND CORE-NOISE

_: Comparisonsof individualstaticand flightjet- and core-noiselevels

I' and-normalizedspectrafor the DC-9-30/JT8D-I09and DC-IO-40/JT9D-SgAare

I) presentedin this section. The differencesbetweenstaticand flightspectra ,_Ill and betweenOASPLsare discussedin terms of the effectsof forwardmotionand

i of engine installation.

!Ill 4.1.I Static-to-FlightCompariSonsof JT8D-IO9Data

I:_i flighttotal low-frequencynoise and individualComparisonsof static _d

ii jet and core n_ise componentsfor the JT8D-I09,correlatedby using primary-i:_ jet velocityas the abscissa,are presentedin flgu_ 72, 73 and 74 for

_ angles of 50°, 90°, and 140°, respectively. At 50° to the inlet centerline

!_ (fig.72), the low-frequencynoise levelsmeasuredin flightcrossedover the

correspondingstatic levelsfor jet velocitiesless than 200 m/sec,because

i:i the core-noiselevelsgeneratedin flightare higherthan the levelsgenerated_,_ statically. The correspondingjet-noiselevels generatedin flightare lower

ii than those generatedstatically. At 90° (fig.73), flightand staticcorei_,

=_ noise are nearlyequal,but the differencebetweenflightand staticjet noise

_: levels has increasedrelativeto the differenceshown in figure72. At 140°

:_ (fig. 74), the measuredlow-frequencynoise and the individualjet and core

. noise componentsare all lower in flight.

:! • In flight,core-noiselevelsare higher in the inletquadrant(fig.72),

" equal at 90° (fig.73), and lower in the exhaustquadrant (fig.74) than the

correspondingstaticdata, which suggestedthat convectiveamplificationcould

be important. The differencesbetweenflightand staticcore OASPLswere

thereforeplottedversus inlet angle for six differentjet velocitieswith

approximatelythe same airplanevelocity(Va = 76.2 + g.o m/sec) and compared

with the convectiveamplificationpredictedtheoreticallyfor a moving point

source. Specifically,the changesin noise levelscaused by the relative

_._

27

00000001-TSC03

I I I' :. I I I I |

motion of a point sourcewith respectto an observeris given by

^OASPL= 40 loglo (I - Ma cos e ) (I)

where Ma is the airplaneMach numberand e is the angle betweenthe inlet

centerlineand the observer (refs.20, 39, and 40). Figure 75 showsgood

agreementbetweenthe data and the predictedresultsfor convectiv__-amplifica-tion of core noise.

mm_,

Comparisonof figures15 and 24 show(_Lno-significantdifferencesbetween

staticand flightcore-noisespectralshapes. But the peak frequencyappeared

to be Doppler-shifted,as is suggestedby figure 76, in which the ratio of the

flight-to-staticcore peak frequenciesis plottedversus inletangle for five

jet velocities,all with the same airplanevelocity.

To investigatethe differencesin jet-noiselevelsbetweenflightand

staticconditionsresultingfrom the combinedeffectof relativevelocity

and convectiveamplification(ref.16), a velocityexponent m was calculated

and plottedversus inlet angle for seven jet velocities(fig.77). The ex-

pressionused to define m is given by

m = AOASPL - lO loglO (l - Ma cos )-l (2)

lO loglo (Vrel/Vjp)

The resultsindicatedthat at inlet anglesless than or equal to 90° the value

of m is approximatelyequal to 3.7. At inlet anglesgreaterthan 90°, m

increaseswith increasingangle. To define the separatecontributionsof

relativevelocityand convectiveamplificationto jet noise will require

furtheranalyses.

Figure 78 comparesstaticand flight normalizedjet-noisespectrafor

angles of 50°, 90°, and 140°. In flight,the normalizedjet spectralshapes

are broader,with higherlevels for all anglesthan the staticspectraat low

Strouhalnumbers. It is not possibleto reconcilethe differencesby consider-

ing Dopplereffectalone. Again, to fully understandthe jet spectral

28

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I l I I, :. l 1 i I I '

differenceswill requirefurtheranalyses.

4.1.2 Static-to-FlightComparisonsof JT9D-59AData

Comparisonsof staticand flighttotal low-frequencynoise and the

individualjet and core noise componentsfor the JTgD-59Aare pre_entedin

figures79, 80, and 81 for angles of 50°, 90°, and 120°, respectively.At

50° (fig.79) and jet velocitiesabove 305 m/sec (jetvelocitiescorresponding ,,.

to takeoffpower),the flightjet-noiselevelsare lower than the correspond-

. ing staticlevelseven thoughthe core-noiselevelsmeasuredin flightare

higher. At lower jet velocitiescorrespondingto approachpower,the fliqht

jet-noiSeand total-noiselevelsare higherthan the correspondingstatic

levelsby as much as 5 dB. At 90° (fig.80) and in flight,the core-noise

levelsare about equal and the jet-noiselevelsare lower. At 140° (fig.81),

boJ;bcore- and jet-noiselevelsare lower in flight. However,at very low

jet velocity (Vjp< 216 m/sec),the decreasein jet noise is considerablylessthan the decreaseobservedat higherjet velocities. The lesseneddecreasein

jet noise at low jet velocitiesis attributedto low frequencynoise generated

by the impingementof the fan jet flow on the trailingflapsof the DC-IO

duringapproachoperation. It shouldbe noted that the primary-jetvelocity

may not be the propercriterionto use for comparingstatic-projectedjet-

noise levelswith flyover-noiselevelsfor high-bypass-ratioturbofanengines

at very low power setting,where the noise from the fan jet can be more

importantthan the noise from the primaryjet.

The highercore noise levels in the inlet quadrant(fig.79), the equal

levelsat 90°, (fig.80), and the lower levelsin the exhaustquadrant (fig.

• 81), show good agreementwith the predictedresultsfor convectiveamplificat-

ion (fig.82). As with the JTSD-I09,there are also no significantdiffer-

ences betweenstaticand flight core-noisespectralshapes. Again, the core

peak frequenciesappearedto be Doppler-shiftedin flight (fig.B3).

Figure84 shows the correlationof the flight-effectvelocity,m, versus

, inletangle for eight jet velocitiesrepresentingdata from takeoffand

approachflyover-noiseruns. The negativevaluesof m for angles less than

29

I /

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- ! I I , 1 I I I

' 90° correspondto the approachcases Th_ velocityexponentsfor the takeoffi'

!; data are positivefor all Inlet anglesand are very similarto those for the

DC-9-30/JT8D-109.The velocityexponentsfor the approachdata.showeda

differenttrend: The exponentsare positivein the _xhaus_quadrantand are

generallylower than the exponentsIn the takeoffdata. It is believedthat

anotherlow-frequencynoise source,uniqueto airplaneconfigurationswith

!: enginesunder the wing such as those of the DC-IO, is responsiblefor theF_

,_ trendobserved in the w_locityexponentobtainedfrom approachdata.

!'_ 4.1,2.1 Maskingeffectof jet-f_apInteractlonnoise.- Figure 3 shows the Il ......... !

! locationof the engineson the DC-IO-4Oairplane. Two enginesare mounted :

!i,i under the wings,and a third is mounted in the verticaltail 68 feet aft of

_ the wing engines. Duringapproach (seefig. 85), parts of the flaps are ex-

!_ tendedout and deflecteddownward,making a flap angle between35° and 50°. A

_ small centralportionof the flap wa.sleft unchanged,to allow the hot jet

_ exhaustfrom the primarynozzle of the engineunder the wing to pass through.

_: It is believedthat the bigger diameterof the fan jet exhaustcaused the flow

il to impingeon part of the deflectedflaps and generateda low-frequencynoise

_" (jet-flap-interactionnoise). To investigatethat effect,flyovernoise from

a DC-lO-lOairplanepoweredby GeneralElectricCF6-6Dengineswas analyzed

for conditionswhere the airplanewas flown at constantairspeedand power

settingbut with differentflap-deflectionangles.

_: Figure86 showsa comparisonof the flyover-noiselevelsfor the airplane

flown at low power settingswith the sameairspeedbut with differentflap-

deflectionangles (0° and 15°). At all inletangles there are no significant

differencesin low-frequencynoise betweenthe two sets of flyovernoise. At

•: a higherpower settingthere are significantincreasesin the low-frequency

(50 to 250 Hz) region of the spectrumfor flap deflectionsgreaterthan 30°.

The increasein low-frequen_ynoise is maximumat inlet anglesfrom 50° to 60°,

smallerat 90°, and zero for angles greaterthan 120° (fig.87). Those

_ resultsindicatedthat for the DC-IO airplanewith enginesunder the win_ and

with flap deflectiongreaterthan 30°, the interactionof the fan jet with the

' flap increasesthe levelsof the low-frequencypart of the spectrumby as much

as 5 dB,

30

• "+ ' ' t+ i• t ., ___ ...... _ ..... - .

00000001-TSC06

I I I, I I I I -! I!I

Jet-flap-interactionnoise has p_ak frequenciesand spectralshapesvery

similarto those of jet noise,and it is difficultto distinguishbetween

their spectra. But since jet-flapinteractionnoise has _ frequencyrange

between50 and 250 Hz, it does not affect the separationof core noise levels

and spectrafrom the measuredlow-frequenCynoiseat power settingcorrespond-

ing to the approachflightconditions.

On the basis of those results,it was concludedthat at high jet veloci-

ties and small _lap deflectioncorrespondingto takeoffconditionsthe jet _.

noise levelswere not affectedby jet-flap-interactionnoise. At low jet

velocitiesand large flap deflectionscorrespondingto approachconditions,

the core-noiselevelswere not affected,but the correspondingjet-noise

levelswere contaminatedby jet-flap-interattionnoise.

4.1.3 ComparisonWith PrOposesANOPP Method

The individualJet- and core-noisecomponentsseparatedfrom DC-9-30/

JTBD-I09and DC-IO-40/JT9D-59Astatic-engineand flyovernoise providean ex-

cellentdata base for comparing,on a noise-soUrce,basis,the predictionof

jet- and core-noiseflighteffectscalculatedby the proposedANOPP method

(ref.20). As are shown in figures75 and 82, the DC-9-30/JTSD-I09and the

DC-IO-40/JTgD-59Adata agreed quite well with the -40 loglo (l - Ma cos o)expressiongiven for the effect of convectiveamplificationon core-noise

levels in flight. The same expressionis used in reference20 to correctcore-

noise levels for convectiveamplification.Comparisonof the predictedand

• the measuredspectralshapesof core noise (fig.88) shows that the ANOPP core

spectralshape is more broad than those derivedfor the DC-9-30/JTSD-I09and

. the DC-IO-40/JTgD-SgA.Also, as shown in figures76 and 83, the core-noise

peak frequenciesfor those data appearedto be Doppler-shiftedin flight,as

the ANOPP method predicts.

Figures89 and 90 comparethe predictedand the measuredjet-noisere-

ductionsdue to the combinedeffectsof relativevelocityand convectiw

amplificationfor the DC-9-30/JTSD-I09and the DC-lO-40/JTgD-59A,respectively.

The figuresshow good agreementbetweenmeasuredand predictednoise reduct-

ions for angles up to and including130'_. For angles _reaterthan 130'_,the

31

T I 'Ii • .......J' I

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'I ! F I ! t I l

predictednoise r_ductionswere consistentlyless than the measuredvalues.

Predictedand the measured.spectralshapes for the jet-noisecomponentfor the

DC-g-30/JTSD-109and DC-10-40/JT9D-59AIn flightare shown in figuresgI and

g2, respectively. Comparisonsof the Jet-noisespectralshapes for anglesof

50° to 120° show that the predictedlevels for both DC-9-30/JT8D-IO9and

DC-IO-4O/JTgD-59Aare lower at the high Strouhalnumbersand higherat the

low Strouhalnumbersthan the correspondingspectrapredictedby the ANOPP

method. At the peak Strouhalnumber,the predictedlevelsshow oood agreement.

4.2 EFFECTSOF FORWARDMOTION,PROPAGATION,AND ENGINEINSTALLATIONON TURBOMACHINERYNOISE

4.2.1 Engine-lnstallationand PropagationEffects

To identifythe effectsof forwardmotionon fan and turbinenoise

sources,the static-projecteddata in figures41, 43, and 46 were first ad-

justedon a sourcebasis for the effectsof engine installation. Figure93

_ shows comparisonsof Dc-g-30flyovernoise levelsand JT8D-109static-pro-

jectednoise levelsat approachpower,correctedfor wing shieldingat an

angle of 30° (fig.93a) and for sound scatteringin the wing-flap-wheelwake

at go° and 120° (figS.93b and c), respectively. In addition,DC-9-30non-

i propulsivenoise levels,which affectsthe static spectraprimarilybelow

blade passingfrequencywere included. Althoughthe agreementbetweenthe

spectrawas improved,applicationsof the barrierand of the sound-scattering

theoriesdid not entirelyaccountfor the static-to-flightdifferences. The

_ remaininghigh-frequencydifferencescould be due.to conservativemodeling

techniquesin the applicationof those theories,but it was thoughtthat the

remaininghigh-frequencydifferenceswere due to the effectsof excessattenu-

ation in the atmosphere.

Figure 94 shows JTSD-I09static-noiselevelsat approachpower corrected

for engine installationand for excessattenuationin the atmosphere(sect.

3.4.2)and comparedwith DC-9-30flyover-noiselevels. The data show that

excessattenuationadequatelyaccountsfor the remaininghigh-frequency

differencesshown in figure93. As a result,it can be seen that the static-

to-flightdifferencesfor the DC-9-30/JTSD-I09airplaneconfigurationare

:'" 32

' ' I '|

00000001-TSC08

!Ill 1 1 t ! I

du_.primarilyto Installatlonand propagationeffects,as opposedto the

_' offect_of forwardmotionon turbomachin_ry-noisegeneration.iii;I; Figures9B and 96 show DC-IO-IOand DC-IO-40flyoverspectracompared

!i wlth CF6-6Dand JTgD-BgAstatic-projectedspectra,respectively,at approach

i power settings,correctedfor relativeenginelocation,fuselageshielding,! jet-exhausL.soundscattering,and nonpropulsivenoise. In the inletquadrant

i , (fig. 95a) and at overheadangles (fig.95b) the engine-installationeffects ,,

• reduce the CF6-6D static-projectedlevelsand improvethe static-to-flight

I,_ . agreementby a small amount for frequenciesat and above blade-passing

frequency. In the aft quadrant (fig.g5c), the correctionsincreasethe

static-to-flightdifferences. For frequenciesbelow blade passing,the

inclusionof DC-IO-IOnonpropulsivenoise levels improvesthe agreementat

the inlet and the overheadangles. Figure96 shows similarresultsfor the

JTgD-59Astatic-projectedlevelscorrectedfor engine installation.Although

the agreementbetweenstatic and flyovernoise levelswas improvedby incor-

poratinginstallationeffectsin the CF6-6Dand JT9D-SgAstatic-enginenoise

levels,significantdifferencesremainat frequenciesequal to ald greater

than blade passag_frequency,

: In section3.4.Z it was shown that when noise data are projectedover

. large differencesin acousticrange,significanthigh-frequencydifferences

':_ due to excessattenuationin the atmosphereare found. Figure97 sl,owsa

_:, comparisonof CF6-6D static-projectednoise levelscorrectedfor excess

attenuationand comparedwith DC-IO-IOflyovernoise levels. In the inlet

: quadrant(fig. g7a), the static-to-flightagreementis improvedfor frequen-

_i: . cies equal to and higherthan blade passing. At overhead (fig.97b), and in

::. the aft quadrant (fig.97c), the correctionfor excessattenuationimproved

. the agreementabove 6300 Hz, where the static-projectedlevelswere higher

At the frequencieswhere fan harmonicsand turbinetones occur in the same

I/3--octaveband, the agreementwas not improved. Figure98(a) shows similar

. resultsin the inlet quadrantfor the JTgD-59Astatic-projectedlevelscorrect-

;, ed for excessattenuationand comparedwith DC-IO-40flyover-noiselevels. At

overhead (fig.gBb), and in the aft quadrant (fig.gSc), where the flight-

noise levelswere higherthan the static-projectedlevels,lessaqreementwas

i: 33

" i' I T I '

00000001-TSC09

! I I I I ! I

obtainedfor a11 frequenciesabove blad_ pa_ing, Althoughthe static-to-

flightagreementwas improvod,significanthigh-frequencydifferonc_ romaln

in the level_of the fan fundamentaltone and In the increasedfllqhtlow1_

at tilefrequencybands containingboth fan harmonicsand turbineton_,

To detemninethe sourcecharacteristicsat those frequencies,narrowband

data were analyzed. Inletand fan dischargeduct measurementswith flush-

mountedKulitemicrophones(ref.9 and fig. 58) have shown that in flightthe

levelsof the fan fundamentalare lower below cutoffand approximatelyequal "'

above cutoff,but that the levelsof the fan harmonicsand of broadbandnoisee

remainedess_ntiallyunchanged. As a result,it was thoughtthat the mecha-

nisms of noise generationfor the fan fundamentaltone during forwardmotion

are differentfrom those under staticconditions. In addition,the high-

frequencydifferencesat overheadand at aft quadrantanglesare the result

of forward-motioneffectson the propagationof turbinenoise and not on fan

noise (sect.4.2.4).

4.2.2 Effectsof ForwardMotion

4.2.2.1 Convectiveamplification.- In order to investigatethe effectsof

forwardmotion on the dynamic,or convectiveamplification(refs.39 and 41)

of turbomachinery-noisesources,static-to-flightdifferencesin the fan-

broadbandnoise levelsat the blade passingfrequencyof the fan were plotted

as functionsof inletangle in figure 99 for the DC-IO-40/JTgD-59Aand DC-IO-

IO/CF6-6D. The fan broadbandlevelsderived in sec(ion3.2.5.2,were used

rather than discretetone levels,because (I) the effectof convectionon tone

levels is masked by differencesbetweenstaticand flyovernoise generationand

(2) narrowbanddata measuredin the inlet duct (ref.9 and fig. 58) show that

the broadbandnoise levelsremainessentiallyconstantwith forwardmotion.

For flightMach numbersequal to 0.282 and 0.296,which are typicalfor high-

approachor takeoffflightspeeds,the data follow the predictedeffectsfor

the motion of a point sourcediscussedfor core noise in section4.1.I. For

low flightspeeds (M = 0.227 and 0.220)the trendsare similarin the inlet

quadrant,but, in the aft quadrantthe flyoverand static levelsare nearly

equal for the peak-aftnoise angles. In the aft quadrant,the increased

flightlevelsrelativeto the predictedconvectioneffectsare similarto the

34

O0000001-TSCIO

II#7.,-

1 ! I 1 I I I I ! I

trends noted earlierIn sectlo_4.2.l for the hlgh frequency_p_ctra. As a

result,th_ discrepanciesat the fan-bladepc_slnqcould be due to increased

turbine-broadbandlevelsoenerat_din flightat tilelow power settinq_.

The 40 log relationship, discussed above, wa_ a_umod to hold for ,_11 fan

speedsfor both fan and turbinenolso sources. Correctlnqthe JTSD-IOg_tatlc=

projectedspectra(fig.94) for convectionwill improvethe st_tic-to=fliqht

agreementas shown In figure lO0. Correctingthe static-projected_pOctrain

figures97 and g8 for the CF6-6Dand JTgD-5gA,respectively,will nut, h(;wever, ='

accountfor thr_remainingdifferenceswhich were assumedto be due to forward

motion effectson sourcenoise generation.

4.2.2.2 Noise generation.- In the followingdiscussions,the effectsof fan-

noise genorationand of the interactionof the fan harmonicsand turbinetones

will be presented. As a resultof trendsnoted in narrowbandspectra (fig.

58), the effectsof fan-noisegenerationwill be restrictedto the blade-

i passing-frequencytone.

The increasedlevel of the fan fundamentaltone under staticconditions

was a_sumedto be due to differencesbetweenthe mechanismsof noise genera-

tion in staticand in flightenvironments. Specifically,under staticcon-

ditions,there is sufficientinflowdistortionto cause the generationof a

strongblade-passing-frequencytone (rotor-turbulenceinteraction)for

approachpower settings(refs.42 through44). The absenceor the reduced

level of the fan fundamentaltone duringforwardmotion indicatesthat the

_ inlet flow is sufficientlyclean and free of disturbancesto enablethe cut-

off conditionsfor which the CF6-6Dand JT9D-59Aengineswere designedto be

realizedat pproachpower settings. Since it is a difficulttask to predict

the theoreticalchange in tone levelsdue to inflowdistortion,an empirical

approachwas used.

The empiricalapproachrequireddeterminationof ti_estrengthand the

directivitycharacteristicsof the fan fundamentaltone from the staticand

flightspectra, The broadbandlevelsat the blade-passinqfrequencydurived

in section3.2.5.2were thereforeused to define the strengthof the fan

i fundamentaltone ih tenllsof the relativelevel of the total f_n noiF,e to the

_. 3b

O0000001-TSC11

1 I I ! I I I ! "

fan broadbandnolso (i,e,,a comparlsQnslmilarto a _Ignal_to-nei_compari-

son) at the bladQ-pa-_singfrequency, The-r_lativ(_l_vel_were obtainedfor a

wide range of anqlesand pewor setting;they are shnwn in flqures101 _nd I02

for the DC-IO.IO/CF6-6Dand DC-lO-40/JT_D-69Aairplanes,r_pectlwly, Th_

data show the increaso.dlevel of th_ statictone relativeto th_ fliqht tnn(_

and the correspondingbroad dlrQctivitypatternat all fan speeds, At sup(,r-

sonic tip spoed_ (NI/VO, 3053 RPM for the CiG-GDand NI//(__ 3212 RPM forthe JTgDo59A),the flyoverdata _how a Inhed directivitypattern,in centre,it

to a relativelybroad shape for subsonictip speeds, At highertip speod_, .,,

static and flightdirectivitycollapsein good aoreement,

4,2.3 Interpretationof Static-to-FlightDifferences

4.2.3,1 Spinning-modetheory.- Interpretationof the differencesbetweenthe

staticlevelsand the flightlevelsof the fan fundamentaltonP requiresiden-

tificationof the three sourcesof noise at blade-passingfrequency- the

rotor-alonesound field,the rotor-starer-interactionsound field,and the

sound field generatedby the interactionof the fan rotorwith unsteadyor

distortedinflow. Tyler-Sofrintheory (ref.45) pointedout the cutoff

phenomenaassociatedwith the spinningmodes of rotor-aloneand rotor-stator-

interactionnoise. At the blade-passingfrequencyof the fan fundamentalfor

a rotor with B bladesand V statorvanes,a criterionwas establishedfor

determiningwhetherthe spinningmode patternof order m would propagateor

decay in a cylindricalhardwalledduct with uniformaxial flow. The criterion

: was given by the cutoff ratio _m as

Mm= 2 (3)

Mm*Vl-Mx

The tip Mach numberof the patternsis given by

BMt" _m : B + _'Y (4)

Those equationsapply for the first radialmode for a spinningnFde of order

m, given by the denominatorof equation (4). Propaoationof the pattern

occurs if 5m is greaterthan unity;decay occurs if _'m is less than unity.For propagatinqmodes, it was shown that the spinning-modepatterntraverses

, ! J ,,• _____- .--,_............................ _.......................................... , ,. I - _• m

00000001-TS012

•. the duct in a spiralan.cjloof propagation_xpre,_edas a functionaf the cir-

cumferentialMath numberof the pattern,

lIQmlc_and Lardl (ref,46) haw. ,_hQwnthat the far-_fi(_lddir(_ctivity

patternuf the duct acou_ti_modm_ can bp.predict_.dby u_Inq _Implp,cylln_

dricalduct theory, Thny shown,d that the locationof thn prlncIpall_bu f'rnm

an m_order._plnnlngmodr_can he approximatedby the _plralanql(_,q,p,_t whlcl_:-, tho patternpropagato_in the duct, A._a r_ult, propaqatlnqm_d()nwith (,ut=

::' off ratiosmuch OrQatorthan unity will propagateat anglo._;of r,liqht inclio

nation to the Inlet contorlinoand mode_with _'m° 1 will propaqat(,at riqht "s angles to the inletcenterlino, If thu inlet flow i_ sufficientlycleat'and

free of distortion_it shouldbe I)Os,_ibleto identifythe modes generatedbyh

: rotor-alonenoise and by rotor-stator-interactionnoi_e by comparim!colou-r..i_ fated and measureddirectivity,

:"_. 4,2,3,2 Sound fieldsof rotOr-aloneand rotor-stato_rjnte.s_ac.tJg_n:.-Figure

=: 103 shows the cutoff ratios for the first three fan harmonicsof the rotor-

_i statorinteraction(rotorwake interactionwith bypass-outletguide van_s)

_- and the first two fan harmonicsof the rotor-aloneas functionsof fan rotorIE,_'

speed for the CF6-6Dengine. Tyler-Sofrintheorywas used to generatethe

data, for which a hardwallcylindricalduct with uniformaxial flow (refs,45

and 47) was assumed, The effectsof inlet length,inletcontour,and acoustic

_.. treatmentwere not includedin the analysis, The cutoff ratioswere calcu-

lated for the first propagatingspinningmode and for the first radialmode,

The figureshows that the fan fundamentaltone due to rotor-starerinteraction

(m =-42) is above cutoff for fan rotor speedsgreaterthan 3130 RPM, The fan

fundamentaltonedue to the rotor-alonesound field (m = 38) is above cutoff

" for fan speedsgreaterthan 2900 RPM. At approachpower settings,tl_efan

fundamentaltone due to rotor-aloneor rotor-statorinteractionshouldthere-

fore decay, Similarresultswere obtainedfor the cutoff ratiosfor JTgD-SgA

" rotor alone (m = 46) and for rotor-statorinteraction(m =-50) at the fan-

blade-passingfrequencyabove fan speedsof 2800 and 3100 RPM, respectively,

The static-to-flightcomparisonsin figureslOl and 102 can now be inter-

preted in terms of the modal constituentsin the radiatedsound field. Figure

" 37

I i 'i I , ,

'i 1 1 I i "-, _,..... •....................................__ j' _...... -I........ "'" " _"

00000001-T8C13

lO] show._that for fan 5p_d_ above a cutoff ratio of unity (NIl,/,, _- 3063),: thp.directlvltyof the_,.DC-IO-IOfllqhtdata _hQw_distinctlobc._at anqle._of

Above 50" and 80r'LQ the inletcenterlln(:,At tlm hlqhercorrectedfan Sl)(,ed

:, af 33_34RPM, the fliqhtdata aqain show lob__,at anqle:__f 50" and BO" and a

!_ broad aft lobe aroundl_(J",Accordinqto th(:approximationsin ref(:rr;nc(_46,

', the flr_t three radialmode_;above cutoff for an m _ 3_ rotoroalone_,plnninq

!'. mode shouldpropafla1_ea£ anule_el_ 50", 61", and 78" to the inlet,r(;slmctive-

i!; ly, At 3384 RPM, the first four radialmode_ shouldpropagateat anfl]e,_,of

"' 42", 52", 63", and 76", respectively,and.the lIrst two radialmode,,for the

ii" rotor-starerinteractionlllode(Ill_ -4_) shouldpropagateat anglesof 121"i', and lOB", respectively,AccordingLu Tyler-_,ofrintheorythe m '--42 rotor-':. stator interactionmode spins in a directionoppositeto that of the fanI'

_,'

i: rotor (contra-rotating),As the contra-rotatingmode propagatesforward,it;: is significantlyattenuatedas a resultof blade-rowtransmissionloss, and

_:" the mode thereforepropagatesto the far field only from the fan discharge

!. ducts. BecauselO° intervalswere used to reducethe flyovernoise data, the

i" individualradialmodes are not clearlydistinguishable.In spite of that,

the flyoverdirectivitypatternfor fan speedsabove cutoff is in good agree-

ment with the predicteddirectivityfor the principalspinningmodes of rotor

alone and rotor-statorinteraction.The correspondingbroad directivity

patternfor the static-projectedlevelscan now be interpretedas the result

of a large numberof modes propagatingout of the duct associatedwith the

interactionof the rotor and inflowdistortion. The strengthof the rotor-

!i distortiontone relativeto the broadbandnoise is essentiallyconstantwith

, increasingfan speed and approximatelyequal to the flight levelsabove cut-

off at the locationsof the principalpropagatingmodes.

FigureI02 shows similarresultsfor the DC-IO-40flyoverand JTgD-59A

static-enginenoise levels, Tyler-Sofrintheorypredictsthe propagationof

an m = 46 rotor-alonespinningmode and the propagationof an m =-50 spinning

mode due to rotor-statorinteractionat the correctedfan-rotDrspeedsof 3212

and 3364 RPM. The approximationsin reference46 indicatethat at a corrected

fan speed of 3212 RPM the first three radialmodes of the m = 46 spinningmode

shouldpropagateat anglesof 55°, 66°, and 77", respectively,relatiw to

the inlet centerline. At 3364 RPM, the first five radialmodes are abuw

O0000001-TSC14

/

cutoffand propagateat angles of approximately30°, 41°, 52°, 63°, and 69°

respectively. In addition,the m = -50 rotor-statorinteractionmode should

propagateout the.fan dischargeducts at anglesof 105° and 120° for the first

two radialsat 3212 RPM and 1.04°, 115°, and 124° fo'-the first three radials

at 3364 RPM. Again, the predictedand measuredflyoverdirectivityare in

_ good agreement.

o

Figure 1_4 shows the measuredflyoverdirectivityfor the DC-9-30at

approachpower i_ comparisonKith the measuredJTSD-lOgstaticdirectivityfor

the fan fundamentaltone. Tyler-Sofri_theoryand reference46 were again

used to predictthe principallobe locationsfor the cuton rotor-I.GY(inlet

guide vane) interactionsm = II a_&-12, which propagateat anglesof small

inclinationto the inletcenterlineout of the inletand fan dischargeducts,

respectively.

For fan speedsbelow Cutoff,r__f.P.rences45 and.46 show that the lobed

directivitypatternsshould be replacedby a broaddirecti_itypatternand

that the blade-passing-frequencytone shouldnot propagate. Wind-tunnel

testingof variousengines(refs.13 and 48) has demonstratedthat for cutoff

fan speedsthe I/3-octaveband containingthe blade-passing-frequencytone is

predominantlybrc._dh_.ndnoise. But figureslOl and I02 show that the flyover

directivitypatternsshow tones propagatingin the inletquadrantat cutoff

fan speeds. FigurelOl shows that the DC-IO-IOflyovernoise has increasing

)i" tone strengthin a broad directivltypatternfor increasingfan speedsup to_ the cutoff point,where the lobed directivitypatterndiscussedpreviously

_=_ dominatesat 3063 RPM. The tone levelsin the far field below cutoffappear

t to be essentiallythe resu_Itof inlet radiatednoise. In comparison,the

static levelsare correspondinglybroad in directivityand of increasedmagni-

tude at all angles. The broad staticdirectivityis indicativeof rotor-

turbulenceinteraction,which resultsin increasedstaticlevelsof the fan

fundamentaltone. Figure 102 Shows similarresultsfor the DC-IO-40flyover

and the JTgD-SgAstaticnoise levels. For fan speedsbelow cutoff,the flight

data snow that the relativelevelsof the propagatingtones are nearly

i constantwith increasihgfan Speed. The levelsappear again to be the result

of inlet-radiatednoise.

39

I _ Ti

00000001-TSD01

L

r t I - I t t I ,_......

There are several possible explanations suggested for the absence of

complete tone cutoff in engines so designed. Reference 49 has shownthat

inlet obstructions such as a protruding temperature probe can disturb the

steady inlet flow, resulting in a mechanismof noise generation by induced

_,_ periodiclift fluctuationson the fan-rotorblades..The mechanismproducesa

, rotor-distortiontone at the blade-passingfrequency. The characteristicsof

'" the rotor-distortiontone can be modeledby the interactionof the rotorwith

_:: the wake from a Single-upstreamstatorvane, w_ich, accordingto Tyler-Sofrin

,_ theory (ref.45), resultsin.a large numberof propagatingmodes at the blade-

__, passingfrequency. Like rotor-turbulenceinteractionunder staticconditions, "_J

_ the multiplepropagatingmodes are characterizedby a broad directivity

_. patternin the_ar field. In addition,the interactionof the rotor wakes

with the core-statorvanes could be cut-Onand could dominatethe fan sound

field when the rotor-ODOGV (outer-diameter-outletguide vane) interactionwas

cutoff. Reference8 has also suggestedthat boundary-layernoise could con-

tributesignificantlybelow cUtoff to the rotor sound field.

.... The propagatingsound fieldsfor the DC-IO-40/JTgD-SgAand DC-IO-IO/CF6-6D_h

Were furtherexamined,in an attemptto find out if the noise mechanismscould

=_ be contributingto the fan levelsbelow cutoff. The core-stator_tage for the

" JTgD-59Aenginehad the same numberof bladesas the outlet-bypassguide vanes

,_ which,accordingto reference45, resultsin a cutoff rotor-statorinteraction

_' mode at the lower fan speedsbeing considered The JTgD-5gAinlet does have

_: an inlet temperatureprobe severalrotor chordsupstreamof the fan-rotorface._,; It was thereforesuggestedthat the rotor-probeinteractioncould be respon-

_; sible for the cutofftone strengthat the blade-passingfrequencyfor the

_i=., DC-IO-40/jTgD-SgAfan-inletlevels (fig.102). But the CF6-6D inlet was free

_;_-_! of inlet obstructions,and the rotor/core-statorinteractionwas also pre-

_: dicted to be cutoff. W_nd-tunneltests of scale-modelfans at cutofffan

_i speeds (refs.13 and 4B) have shown completeabsenceof tones at the blade-

..... passingfrequency,which would tend to eliminatethe boundary-layernoise as_._;

_; a principalsourcebelow cutoff. Since the directivityof flyoverlevels

_i below cutoff is similarto that of the staticlevels (fig.lOl), the flyover-_,: tone levelsin the inletquadrantwere attributedto residualinflow

turbulencein the flightenvironment. The phenomenonof completetone cutoff

40

/

in wlnd-tunneltests may be the resultof levelsof turbulencein the test

i. see:iontoo low to slmul_tethe actualflightenvironment. The effectsof

! inflowturbulenceon the DC-IO-40/JTgD-59Aflightlevelsmay be masked by the

more efficientrotor-probenoisemechanisms. One consequenceis that the use}

_ of wind-tunneltestingWithoutregard to in-flightturbulencelevelsmay

underpredictthe flightlevelsat the fan-fundamental-tonefrequency.!:

I' 4.2.3.3 Fan-fundamentaltone correction.- The proceduresused to correctthe

i; Static-to-flightdifferencesat the blade passingfrequencyof the fan funda-em_

,_ mental tone for the effectsof noise generationare describedbelow. The

if correctionsaccountfor the static-to-flightdifferencesas functionsof

_. directivityangle, fan-rotor-tipMach number,and circumferentialmode number,

m. As a first step, the broadbandnoise contributionto the relativelevels

,; of figureslOl and I02 was removed,to yield the absolutetone levelsas

functionsof fan=rotor-tipMach number. For fan Speedsbelow cutoffan

aVeragelevel of the staticand flyoverfan__undamen_ toneswas obtainedin

_ inlet and.aft quadrants..Above cutoff,the lobes in the flyoverdirectivity_:'_- patternwere removed temporarily,to give a broad directivitypatternfrom

i_i which an averageinletand aft-quadranttone level could be derivedandcomparedwith the averagelevelsderivedfrom the staticdirectivity. The

ii increasedfTight levelsat the principallobe locationswere accountedfor by• a directivitycorrectiondescribedlater. The modifieddirectivityabove cut-i:

off allows an averageinlet and aft quadranttone level to be derived. Figure

105(a)Shows thee_fectof fan-rotortip Mach numberon _he level of the fan

• fundamentaltone in flightand the turbulence-generatedtone under staticcon-

i ditionsfor the DC-IO-IO/CF6-6Dairplane. At the fan speedsexaminedthe levelsof the statlcallygeneratedtone were uniformlyhigherthan the correspondi_;U

flightlevels. Again, above cutoff the statlc-to-flightdifferencesreflect

averagedifferenceswithout the contributionfrom propagatingduct acoustic

_il modes. In the inlet quadrant,the levelsincreasewlth tip Mach number until

_!. sonic tip speedsexist where the levelsdecreasewith increasingtip Mach nUmber.

In the exhaustquadrnat,the static levelsare higher than the flightand increase

with tip Mach number except that above cutoff the levelscontinueto increase

with tip Mach number. Similarresultsfor the inlet and exhaustquadrantsare

shown in figurelOS(b)for the DC-IO-40/JT9D-59A.The inlet static levelsarer,

41

iii I

00000001-TSD03

I! I 1 1 ! { ', I!Ii_ again higherthan the flight levelsfor subsonictip speedsand are equal to

_ the flightlevels for supersonictip speeds. In the aft quadrant,however,_: the absolutelevelsfor supersonictip speed_decrease in contrastto the

_ trends for the DC-IO-IO/CF6-6D(fig.105(aJ).

T

II The staticand flight levelsshown in figureI05 were used to determine

i the static-to-flightcorrectionshown in figureI06. Figure 106(a)show_-that in the inlet quadrantthe statlc-to-flightdifferencesfor the DC-IOair-

li planesare consistent. The figureshows that the relativelevelsfor theDC-IO-I_/CF6-6Dand DC-lO-40/JTgD-59Aare consistenta_d decreaseuniformly

i: wi±h increasingtip Mach number. In the exhaustquadrant(fig.106(b)),iFilo the relativelevelsare again consistent,remainingc. _tant until approxi-_i_ mately sonic tip speeds,where the relativelevelsoecreaseuniformlywith;.

_' increasingtip speeds. To correctfor forwardmotion,the staticlevelsof

the fan fundamentaltonewere thereforereducedin the i__letquadrantby the

)i levels in figure106(a)for angles up to 70° and in the aft quadrantby the

levels in figure106(b) for angles greaterthan lO0°. For overheadangles,

a_ averageof the two curveswas used. To accountfor the shape of the flight

directivity,the approximationsin reference46 were used to determinethe

anglesof principal-lobelocation. At those angles,the staticand flight

levelsare approximatelyequal (figs.lOl and I02). The correctionmethods

were thereforenot appliedfor the angles of propagatingmodes. With the

iii! directivityand the levelcorrection,the static levelscan be correctedat

= all anglesand power settingsto approximatethe measuredflightlevels.

The resultsof includingthe correctionsto those of fan fundamentaltone

for nOise-generationeffectsand for convectiveamplification,with the

correctionsfor engine installationand propagation,are shown in figuresI07

and I0_ for the DC-IO-IO/CF6-6Dand DC-IO-40/jTgD-5gA,respectively. Figure

: 107(a)shows that significantimprovementis achievedb_ correctingthe

CF6-BD-statictone levelsat the blade-passingfrequencyfor noise-generation

. effects. Figure lOT(a)shows that below blade passingfrequency,inclusion

of the efl=ectsof convectiveamplificationimprovesthe static-to-flight

agreement. In the aft quadrant(fig. 107(c))there is betteragreementfor

frequenciesgreaterthan 5000 Hz, but at the blade passingfrequenciesof the

turbineand fan harmonicsthere are less agreement. Similarly,figureI08

42

O0000001-TSD04

! I I I I !, I

shows that inclusionof the effectsof noise q_nerationon the _ade-passlnq

frequencytone improvesthe JTgD-SgAstatic-to-flightagreemBnt. In the inlet

quadrant(fig. IOB(a)),th_ inclusionof convectioneffectsimprovesthe

agreementat the b_oadbandfrequenciesbetweenthe fan first and secondharmo-

: nics and at the high frequenciesabove 6300 Hz. In the aft quadrant(fig.

I08(c)),there is less agreementseen at all frequenciesexceptat the blade-

passingfrequency.

Figures109 and II0 show that, in general,the remainingdifferencesare "

th_ higherstatic levels in the inlet quadrantand the lower staticlevels in

the aft quadrantat approachpower s_ttings. At takeoffpower settings,the

DC-IO-IO/CF6-6Dcomparison_show higherstaticlevels in the inlet quadrant,

exceptat 50° from the inlet,with otherwisegood agreement. The DC-lO-40/

JT9D-59Acomparisonsshow higher staticlevels in both inlet and aft quadrants.

In figure 107, the higherCF6-6D staticlevels in the inlet quadrantare due

to differencesat frequenciesgreaterthan 3150 Hz. The static-to-flight

differencesin the aft quadrantare due to the reducedstaticlevelsat the

fan-harmonics/turbine-blade-passingfrequencies. In figure108 the agreement

is relativelygood in the inlet quadrant,,but less agreementis found at the

' fan-harmonic/turbine-blade-passingfrequencies. FigureIll shows that at

takeoffpower the static-to-flightdifferencesfor the DC-IO-IO/CF6-6Dare

due to the propagationof MPT noise in flightand the higherstaticlevels

above 2500 Hz. Figure I12 shows that for the DC-lO-40/jTgD-SgAthe propa-

gationof MPT noise is not a factor and that the static-to-flightdifferences

:. are due to the higherstatic levelsfor the fan harmonics.

_" The correctionsto the fan fundamentaltone for forwardmotion effectsI

were not appliedto the JTBD-IOgfan levelsas comparisonsof far field data

did not exhibitappreciabledifferencesat the blade passingfrequencyafter

inclusionof engine installation,propagationand convectioneffects. Figure

I13 shows that the remainingstatic-to-flightdifferencesin PNLT are

negligiblein comparisonto those for the DC-IO-|O/CF6-6Dand DC-IO-40/

JTgD-59A.

43

.... iF..... _i I

00000001-TSD05

ri! !; I I I L I II

• 4.2.4 High-FrequencySpectralDifferences

_i In summary,the prominentstatic-to-fliqhtdifferencesin turL_;,mchinery

noise levelsare at takeoffpower,where, in flight,MPTs propagat_out the

_, inlet at frequenciesbelow blade passing,and at approachpower,where turbine_ and fan discretetones occur in the same I/3-octaveband. To accountfor the

propagationof MPTs in flight,more work will be requiredto accountfor the_;

effectsof inletcontouron the inlet wall velocitiesduring staticand _light

!': operation. At approachpower settings,the flight levelswere hinherthan ,.

/i thosemeasuredstaticallyat the fan/turbine-blade-passingfrequ_,.ies. To

_, accountfor the diffe.'ences,the staticand flightsourcecharacteristicshad;/

to be examined.

! In section4.2.2.1,the predictedeffectsof convectiveamplification

were fou_ to differ from the measureddata in the aft quadrantat approach

_ill power settings. Figure114 shows typicalcomparisonsof noise data from

,!i Kulite (flush-mounted)microphonesin the CF6-6D fan-dischargeducts during

,,i!ii staticand flyoveroperation. The levelsof the fan harmonicsand broadband

noise remainessentiallyunchanged. Figure 51 comparedthe turbinenoise

suppressionduring staticand flightoperationmeasuredwith and withoutan

acousticallytreatedturbinereverserinstalledin the CF6-6D. More noise

reductionwas measuredin flight,which suggeststhat turbinenoise increases

duringforwardmotion (figs.107 and 108).

• To investigatethe differencesfurthe,',the directivityof the tone

levelsat the I/3-octavebands containingboth fan and turbinenoise were

examinedin a manner similarto that describedin section4.2.2.2. FigureIf5

presentsa comparisonof DC-IO-IOflyoverand CF6-6D static-correctedlevels

and directivityfor the I/3-octaveband containingthe fan secondharmonic,

which is also sharedby one or more turbinetones. At takeoffpower settings

the relativetone strengthsare equal. At approachpower settings,however,

the flightdata are higherat overheadand aft quadrantangles. The static

and the flyoverdirectivitiesappear to cross. The effectsof sourcegenera-

tion or inflowturbulencewould tend to make the staticlevelshigher,which

is contraryto the aft-quadrantresults. In addition,since the fan harmonics

are well cuton, the rotor-stator-interactionmodes shouldpropagateat angles

44

' ' t L I ....

00000001-TSD06

I I I _ 1 I I I !_ !

of shallowinclinationto the inletcenterline,which suggeststhat modal

constituentsare not the cause of the observeddifferences. Slmilarresults

are shown in figure I16 for the DC-lO-40/JTgD-59Aat the third harmonic

frequency.

It was thoughtthat a scatteringphenomenonsimilarto that describedin

reference29, occurringin the CF6-6Dand JTgD-59Afan ambientshear layers

was responsiblefor the apparentattenuationof turbinenoise in the aft

quadrantunde_ staticconditions. It has been shown that the fan ambient ,_.

shear layer is thickerstaticallythan the flightshear layer (fig.52). The

applicationof the effectsof jet-exhaustsound scatteringto the levels

describedin section4.2.1 did not, however,accountfor the static-to-flight

differences. As a result,it was suggestedthat the turbinelevelS,spectra,

and directivities,which were derivedfrom staticdata, are insufficientand

that more work would be requiredto define the staticlevelsand the effects

of forwardmotion on _,_hln_-nILisepropagation.

45

] i

00000001-TSD07

I .I i I I I t iBB

__ING PAGE. BL_K N(_.

5. STATIC-TO-FLIGHTCORRECTION

The use of staticenginenoise data to predictairplane/engineflyover

• noise requiresthe separationof the totalmeasuredlevels into the principal

noise sourceswhich include:

I. Jet Noise_i 2. Core Noise

3. Fan Inlet Noise4. Fan ExhaustNoise5, TurbineNoise

Based on the desiredflight path profile,each engine noise-sourcelevels

_ must be extrapolatedto the far field using the enginedirectivityangle and

: " acousticrange unique to each engineon the airplane. The sourcelevelsare

then correctedfor sphericaldivergenceand atmosphericabsorptionusing

standardtechniques.

i In addition,each enginenoise sourcemust be correctedfor the effectsi"

_ of engine installation,atmosphericpropagation,and forwardmotion.JET NOISE - ExcessAttenuation

RelativeVelocityExponent- m (or ANOPP method)

. CORE NOISE - ExcessAttenuationDopplerShiftConvectiveAmplification

FAN INLET - Wing/FlapShieldingWing/Flap/WheelWake Sound ScatteringFuselageShieldingInletContourExcessAttenuation

_ DopplerShiftConvectiveAmplificationNoise Generation- Rotor - TurbulenceInteraction

FAN EXHAUST - Wing/Flap/WheelSound ScatteringExcessAttenuationDopplerShift

, , ConvectiveAmplification" Noise Generation

TURBINE - Wing/Flap/WheelWake Sound Scattering_ Jet ExhaustSound Scattering!LI ExcessAttenuation

DopplerShiftConvectiveAmplification

In addition,sourcesof airframeor nonpropulsivenoise and jet/fidp

interactionnoise must be includedin the flyovernoise prediction.

i: 47

,°

L 'i .

O000OO01 -T.'q NN,R

6, CONCLUSIONS

ii The effectsof forwardmotionon airplane_enginenoise were invontigated

by comparingseparatedengine-noisesourcesfrom _tatic-enginoand flyover

noise data for DC-9-30/JT8D-I09,DC-IO-IO/CF6-6D,and DC-lO-40/JTgD-59A

airplaneconfigurations.The resultsare sun_narizedbelow.

I. Static-enginedata shouldbe adjusted,on a noise sourcebasis, for

the effectsof forwardmotion,engine installation,and propagationand then

projectedto flightconditions,for each engineas functionsof sourcepath-

angle,directivityangle, and acousticrange relativeto the groundmicrophone.

2. The effectof convectiveamplificationon core-noiseand turbo-

machinerynoise levelscaused by the motion of the engineswith respectto an

observeragreedwith the theoreticalrelationship,-40 log (l - Ma cos o),

derivedfor a moving point source.

3. The shift in core noise peak frequencyagreedwith Dopplershift

: effects,(l - Ma cos e).

4. At all anglesof inclinationfrom the inletcenterline,the levels

of Jet noise generatedin flightwere lower than those generatedstatically.

The largestdifferencesoccurredin the exhau)tquadrant. The lower levels

measured in flightare due to the combinedeffectsof relativevelocityand

convectiveamplification. Furtheranalysesand testsare requiredto

determinethe separatecontributionsof those effectson jet noise.

5. In flight,the normalizedjet spectralshapeswere broader,with

higherlevelsat low Strouhalnumbersthan those of the staticspectra. Those

spectraldifferenceshad been observedat all angles. It was not possibleto

reconcilethe differencesby consideringDopplereffectalone and to under-

stand them will requirefurtheranalyses.

6. For the DC-IO airplanewith enginesunder the wing and flaps with

i: flap deflectiongreaterthan 30°, the jet-flap-interactionnoise qeneratedby

the impingementof the fan-jetexhauston the deflectedflaps,was responsible

_, for higherlow-frequencynoise levels in flightduringapproachconditions.

F; 49

+

m - • - • . L, ,,, ,

00000001-TSD09

In the inlet,the effectcan b_ as much as 5 dB. It wa_ sign|ficantly

less for the exhaust.

7. The difforencesbotwo_nstaticand flightjet noise level_wer_

corrolatedin terms of a relativevelocityexponentas a functionof direc-

tivltyanglo. The correspondingexponent_for the DC=9-30/JTBD-109and the

DC-lO-40/JT9D-59Afollowedsimilarcurves.

8. Comparisonsof measuredand ANOPP-predictedJet noise reductionsfor

the Dc-g-30/JT8D-IOgshowedgood agreementfor angles of 40 degreesto 130

degrees. The predictedJet noise and core noise spectralshapesshow good

agreementat the peak frequenciesfor both the DC-g-30/JTSD-IO9and DC-IO-40/

JTgD-59A. At the higherfrequenciesANOPP overpredictsboth Dc-g-30/JTBD-I09

and DC-IO-40/jTgD-BgAlevels. At the lower frequenciesANOPP overpredicts

DC-9 levelsand underpredictsthe DC-IO levels. The jet noise reductions

predictedby ANOPP for the DC-IO-40/JT9D-SgAare in good agreementwith those

measuredat higherjet exit velocities,however,the levelsat the low to

mid velocitiesare overpredicted.

g. The static-to-flightdifferences(thedifferencesbetweenstatic-

projectedand flyover-noiselevels)for the DC-g-30/JTSD-IO9airplaneswere

found to be due to wing shielding,wake sound scattering,and convective

amplification.

lO. For approachpower settingsthe effectsof engine locationand of

fuselageshieldingon DC-IO flyovernoise are canceledby the effectsof con-

vectiveamplification. The improvedagreementin the mid-frequencyrange is

obtainedby includingDC-IO nonpropulsivenoise in the static-projectednoise

levels.

II. The high-frequencystatic-to-flightdifferenceswere shown to be

smallerif excess attenuatlonin the atmospherewas taken intoaccount.

Furtheranalysesare requiredto more accuratelydeterminethe absorption

coefficientsas functionsof altitudeand frequency.

12. Acousticmeasurementswith far-fieldmicrophonesindicatethat the

static-to-flightdifferencesin fan noise are due primarilyto differencesin

noise generationat the fan-blade-passingfrequency. Staticdata are

50

' i J I ii °i

L .... "........ • ............ • .... •.......... | " '....

O0000001-TSDIO

characterizedby a broad directivitypatternwith increasedlevelsdue to

inflowdistortionthatmust be correctodto the lobeddirectivityin flight,

which i_ due to the propagationof _plnningand radialmodes for rotoroa'lono

and rotor-statQrIntoractlontones above cutoff.

13. The presenceof propagatingfan tono_ in flyoveronoisemeasurom(_nt_

at cutofffan speedswas attributedto residualinflowdistortiondurinq

forwardmotion. Furtheranalysiswill be requiredto isolatethe particular ,.

noise mechanismsthat generatethe blade-passing-frequencytone.

14. MOre work will be requiredto define the effectsof inletcontour

on the propagationof multiple-pure-tonenoise at supersonicfan tlp speeds.

15. The remainingstatic-to-flightdifferencesare characterizedby the

increasedflight levelsat the I/3-octavebands containingboth fan harmonics

and turbinetones. Measurementshave suggestedthat the fan harmonicsand

•, broadbandnoise are the same in staticand in flightconditions,which suggest

that turbinenoise becomesmore prominentin flight. It is thoughtthat a

scatteringphenomenonis responsiblefor reducedstaticlevelsof turhine

noise in the aft quadrant. More work is requiredto definethe turbine

spectrumand the directivityshapesunder staticand under flightconditions

and the effectsof forwardmotion on turbine-noisepropagation.

/i

• The resultsshow the importanceof properlyidentifyingstaticand flight

enginenoise sourcelevels,spectra,and directivitiesand of adjustingthe

staticnoise levelsfor forwardmotion on a noise sourcebasis.

51

.... c........'.'J

"W"......., ,,,, ,,'III I _T ....

O0000001-TSD11

1 I ' I !li '' ' t i •, l

iL

_R_I_)INQ pA_.B}BLANK NOT FIL_

C_'- l, SYMBOLS

Ap prlmary nozzle area, m2

B numbor of fan rotor blad_

BPF blade passingfrequency,llz

B1 fan boosterstage BPF, Itz

dB Decibel

D, Dp diameterof primarynozzle,m

, f l/3-octave-bandcenterfrequency,Hz

fpeak core noise peak frequency,Hz

F fan BPF, Hz

Hz Hertz

m fllght-effectvelocityexponent

m circumferentialmode number

M, Ma airplaneflightMach number

Mm tip Mach numberof spinningmode pattern,?,

- Mm* cutoff tip Mach numberof spinningmode pattern

Mt fan-rotortip Mach number

Mx axial Mach numberof inlet flow

MPT multiplepure tone

i N staticcore-nolseOASPL versusjet velocitycorrelationslopei

' OASPL overallsound pressurelevel,dB

PNLT tone-correctedperceivednoise level,dB

. , SPL sound pressur_level,dB

•. T turbineBPF, Hz

V numberof fan statorvanes

53

00000001-TSD12

.... Va airplanef11ght_peed,m/._ec

Vj primaryJ()tvelocity,m/,_(_c;.. P

,. Vro] relative.Jet velocity,Vjp_Va, m/_oc

us exces_ attenuationcoefflcient_ dB1330m

^OASPL differencebetweenstaticand flightOASI'L,dB -.,

.:, ASPL differencebetweenstaticand flightSPL, dtl

_. aAlt differencein slant rang_ for proJ(_ctionon onO spectromto another,m

_'m cutoff ratio of mth circumferentialmode

_. {_ angle betweeninlet centerline and observer,deg2,_ variancedefinedas the sum of the squareof the differencesbetween

measuredand estimatedSPLs for l/3-octave-bandcenter frequencyto to I0,000Hz

• % principallobe locationfor a particularcircumferentialand_. radialmode number,deg..!

i_,,

54

' I J I...... "L-_. _._.- _ J'..... - | ,- , , : _i i _"_ J

00000001-TSD13

, I ! . L I I ', I !

.!.

' REFERENCES,,pt

l Anon , "J_t N_'isePr_dlctlon" !incietyof Automotive:Ei;qlne(_r_,AIR _76i: " t t ! ,

i

t, 2_. Colrts,G. M., "Er,timatingJet Noi*ie"o, Aer(_rauti(:alQuart(:rly,Vol. 14,

ill 1963.

i,, 3, Ffowc._Williams, a E , "The Noise from Turbulence Convected at llighi i ,

b Speed",PhilosophicalTransactionsof the R(_.yalSociety,Vol. A2_5,. jlb,i

I:" 1963, pp. 469-503.ID*

Z" 4. Busllell, K. W., "Measurement and Prediction of Jet Noise in Flirlht",

i,:,. AIAA PreprintNo. 75-461,Hampton,Virginia,1975."727/JI'81_Jet and Fan Noise Fli(]htEffects,FAA-I)-76-110,5. Munoz, L. J.,

August 1976.

.. 6. l.lerriman,J. E. et• al•, "ForwardMotion and Install_tionEffectson

" EngineNoise",AIAA preprintNo. 76-584,Pale Alto, California,1976.

:i 7, Feller,C• E•, and Merriman,J. E., "Effectsof ForwardVelocityand

,._' AcousticTreabnent.on Inlet Fan Noise",AIAA PreprintNo. 74-946,Los

Angeles,California.

_,_ I_. Clmllpsty,N. A•, and Lowrie,B. W., "The Cause of Tone Generationby

AeroengineFansat High SubsonicTip Speeds and the Effectof Fonvard

Speed",ASME PreprintNo. 73-WAlGT-4,Detroit,Michigan,1973•

9. Merriman,J. E., and Good, R. C., "Effectof ForwardMotion on Fan

Noise",AIAA PreprintNo. 75-464,Hampton,Virginia,1975.

lO. Plucinksy,J. C , "QuietAspectsof the Pratt and WhitneyAircraftJTl5

,:, Turbofan",SAE BusinessAircraftMeeting,Preprint730289,1973,

Wichita,Kansas•

If. Roundhill,J. P., and Schaut,L. A., "Modeland Full Scale Test Results i

' Relatingto Fan Noise in FlightEffects",AIAA PreprlntNo. 75-465,

'. Hampton,Virginia,1975._.i;" 12. Lowrie,B. W., "Simulationof FlightEffectson Auro Engine Fan Noise",

AIAA PreprincNo. 75-463,Hampton,Virginia,1975.

"Simulationof Fli(lht-TypeE.w,jine13. Heidmann,M. F., and Dietrich,D.A., .

Fan No_se in the NASA-Lewis9 x 15 AnechoicWind Tunnel"NASA

TMX-73450,1976.

55

O0000001-TSD14

14. Zwieback,E. L., "FlyoverNoise TestingQf CommercialJet Airplanes"

AIAA Journalof Aircraft,Vol. lO, No, 9, 1973, pp. 538-542.

15. Packman,A. B., Ng, K. W. and Paterson,R. W., "Effectof Simulated

ForwardFlighton SubsonicJet ExhaustNoise",AIAA PreprintNo. 75-869,

F" Hampton,Virginia,1975.

16. Cocking,B. J. and Bryce,W. D., "SubsonicJet Noise in FlightBased on! .

Some RecentWind-TunnelReSults",AIAA PreprintNo. 75-462,Hampton,

_ . Virginia,1975.mml_,

17. Cocking,B. J., "The Effectof Flighton SubSonicJet NoiSe" AIAA '

PreprintNo. 76-555,Palo Alto, California,1976.I

18. Tanna,H. K. and Morris,P. J., "InflightSimulationExperimentson

TurbulentJet Mixing Noise" AIAA PreprintNo 76-554,PaloAlto.,r '

i- California,1976.

19. DeBelleval,J. F., Chen, C. Y. and Perulli,M., "Investigationof

InflightJet Noise Based on Measurementsin an AnechoicWind Tunnel",

;, Paper presentedat the 6th InternationalCongresson Instrumentationin

AerospaceSimulationFacilities,Ottawa,September1975.r---

i_' 20. Stone,J. R., "FlightEffectson ExhaustNoise for Turbojetand Turbofan: Engines- Comparisonof ExperimentalData with Prediction". NASA

i TMX-73552,1976.

;i 21. "DC-9 FlightDemonstrationwith RefannedJT8D Engines- Final Report,h '

i. Volume IV, FlyoverNoise",NASA CR-1348bO,DouglasAircraftCompany,1975._. 22. "StandardValuesof AtmosphericAbsorptionas a Functionof Temperature!,

!_ and Humidityfor Use in EvaluatingAircraftFlyoverNoise",SAE ARP 866,, August 31, 1964.

23. Munson,A. G., "A ModelingApproachto NonpropulsiveNoise",AIAA

i.! PreprintNo. 76-525 PaloAlto, California,1976.LI,i 24. Mathews,D. C., Rekos,N. F., "DirectCombustionGenerated)_oisein

TurbopropulsionSystems- Predictionand Measurement",AIAA Preprint

. No. 76-579,Palo Alto, California,1976.

?S. "FinalReporton Phase II Programfor Reran JTSD EngineDesign,Fabrica-E

: tion and Test", NASA CR-134876,Pratt and WhitneyAircraftCompany,1975.

): 26. "Core EngineNoise ControlProgram- Volume Ill - PredictionMethods",

:_C FAA-RD-74-12,III, AircraftEngineGroup - GeneralElectricCompany,

i' 1974.

00000001-TSE01

27. Krejsa,E. A., and Valerino,M. F., "InterimPredictionMethodfor

TurbineNoise",rIASATMX-73566,1976.

: 28. Beranek,L. L., "Noiseand VibrationControl",McGraw-HillBook Co.

(1971) pp. 174-178.

_dd, M. J , "Note on the Scatteringof Sound in Jets and the Wind"$

Journalof SOund and Vibration,Vo1. 26, No. 4 (1973),pp 551-560.

30. Candel,S. M. and Julienne,A., "Shiel(Li_.gand Scatteringby a Jet

Flow",AIAA PreprintNo. 76-545,PaloAlto, California,1976.

31. DeLoach,R., "On the ExcessAttenuationof Sound in the AtmoSphere",m

_ NASA TND-7823,March 1975.

32. Beran,D. W., Reynolds,R. M. and Gething,J. T., "SoundAttenuationin

the Free Atmosphere",PublicationNo. 17, ProjectEAR, ReportNo. V,?

MeteorologicalDepartment,Universityof Melbourne,December1970.

33. Beran,DonaldW., "TurbulenceDetection",Ph.D. Thesis,Universityof

Melbourne,July 1970.

_ 34. Benson,R. W..and Karplus,H. B., "SoundPropagationNear the Earth's

: Surfaceas Influencedby WeatherConditions",WADC TechnicalReport

.'" 57-353,Part I, U.S. Air Force,March 1958. (Availablefrom DDC as

AD 130 793.)

35. Burkland,M. D., Karplus,H. B. and Sabine,J. J., "SoundPropagation

: Near the Earth'sSurfaceas Influencedby WeatherConditions",WADC

TechnicalReport57-353,Part II, U.S. Air Force,December1960.

36. Sabine,H. J., Raelson,V. J. and Burkland,M. D., "SoundPropagation/-

-.) Near the Earth'sSurfaceas Influencedby WeatherConditions",WADC

i, Techni:alReport57-353,Part III,U.S. Air Force,January1961.

i"" 37. Sabine,H. J., "SoundPropagationNear the Earth'sSurfaceand Influenced

.. by WeatherConditions",WADC TechnicalReport 57-353,Part IV, U.S.

._ Air Force,January1961.! 38. Beran,D. W. and Gething,J. T., "Use of a Sailplanein Measuring

AcousticAttenuationin the Atmosphere",Aero-Revue,Issue2, February

:: 1972, pp. 93-95.

_ 39. Lighthill,M. J., "SoundGeneratedAerodynamically",The BakerianLecture

_. 1961. Proc. Roy. Soc. (London),Vol. 267A, 1972, pp. 147-182.

:, 40. Lowson,M. V., "The Sound Field for Singularitiesin Motion",Proc.L

Roy. Soc. (London),Vol. 286A, 1965, pp. 559-572.

41. Crlghton,D. G., "Scatteringand Diffractionof Sound by MovingBodies",

_. Journalof Fluid Mechanics,Vol. 72, Part 2, 1915, pp. 209-227.

42. Mani, R., "NoiseDue to Interactionof InletTurbulenceWith Isolated

Statorsand Rotors",Journalof Sound and Vibration,Vol. 17, No. 2,

July 1971, pp. 251-260.

43. Pickett,G. F., "EffeCtsof Non-UniformInflowon Fan NcuLse",Paper

,_o B5 presentedat the 87t_,meetingof the AcousticalSocietyof America,

i,. New York, New York, April 1974, also J. Acoust.Soc. Am., 55, S3(A),

il. Spring 1974.

i_ 44. Clark, B. J., Heidmann,M. F., and Kreim,W. J., "MicroscopicStudy of

_ Time UnsteadyNoise of an AircraftEngineDuring StaticTests",NASA "

TMX-73556,1976.

45. Tyler, J. M. and_Sofrin,T. G., "AxialFlow-CompressorNoise Studies",

Transactionsof the SAE, Vol. 70, 1962, pp. 30g-332. _I

46. HomicZ,G. F., and Loudi,J. A., "A Note on the RadiationDirectivity 1

Patternsof Duct AcousticModes",Journalof Sound and Vibration,Vol.

41, 1975, pp. 283-290.

47. Sbfrin,T. G., and McCann,J. C., "Prattand WhitneyAircraftExperience

in CompressorNoise Reduction",Paper 2D2 presentedat the 72nd meeting

of the AcousticalSocietyof America,Los Angeles,California,November

1966; also J. Acoust. Soc.Am., 40, 1248(A),No. 5, 1966.

48. Dietrich,D. A. and Heidmann,M. F., "AcousticSignaturesof a Model

_ Fan in the NASA-LewisAnechoicWind Tunnel",NASA TMX-73560,1977.

4g. Hodder,B. K., "FurtherStudiesof Staticto FlightEffectson Fan Tone

i_" Noise Using InletDistortionControlfor Source Identification",NASA

TMX-73183,1976.

).

58

00000001-TSE03

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!"" 36.30 m _! _J_,_.

3.35m _ _"

,_'"_1 . ,_.,...- _2.32,,1 "-_ .....16.22.1 -

...... 32.61m

(a) DC9_30 AIRPLANE GEOMETRY

t

(h) ,IIHI) Ill!) ENf.IINL/NAI:LI I.E

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=" FIGURE 1. DC-9.30/JTSD-109AIRPLANE CONFIGURATION

66

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n...........i.....: I_ II

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5 Ui'-m

* H.41 m thbLIn_; _,Ul m .

(U) DC-10-10AIRPLANE GEOMETRY

(b) C16-6D WING ENGINE/NACELLE

FIGURE 2. DClO10/CF66D AIRPLANE CONFIGURATION

67

' 'l _ ' 1 J i "i. ' " ...... _ ......... J' - .... I ....... ,

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(b) JT9D-59A WING ENGINE/NACELLE

FIGURE 3. DC.10.40IJTgD-SgA AIRPLANE CONFIGURATION

68

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00000001-TSE13

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FIGURE13. NORMALIZEDSPECTRAOF JTSD.109STATICJET.PLUS.CORENOISEAT 4E.7-METERRADIUS. Va - 0 M/SEC

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FIGURE 13 NORMALI;)ED SPECTRA OF JTSD-'m09STATIC JET-PLUS-COl:I):NOISE AT 45.7.METER

I_ADIUS. Va = 0 MISEC

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FIGURE 15. NORMALIZED SPECTRA OF JTSD-IO9 STATIC CORE AT 45.7-ME't_R RADIUS

PRI,X:IN(;IPA,OUt,AN1K:82

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FIGURE 15 NORMALIZED SPECTRA OF JTSD-109 STATIC CORE AT 4_.7-METER RADIUS (CONTINUED)

83

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5- FIGURE '16 NORMALIZEDSPECTRAOF JTgD-59ASTATICJET-PLUS-CORENOISi:AT 45,7-METER: RADIUS, Va = 0 M/SEC(CONTINUED)ii

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(a) 50° FROM INLET CENTE_KLINE

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(b) 90 ° Fl¢Oh INLET CENTERLINE

FIGURE 17. NORMALIZED SPECTRAOF JT_D.EgA STA_'IC CORE NOISE AT 45.7.METER RADIUS

88

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, (d) 140° FROM INLET CENTERLINE

FIGURE 17 NORMALIZED SPECTRAOF JTgD-59A STATIC CORE NOIJE AT 45.7-METIER RADIUS(CONTINUED)

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i' FIGURE 22. NORMALIZED SPECTRA OF DC-9-30tJT8D-I(]I9 INFLIGHT JET@LOS-CORE NOISE AT 45.7WIETER. RADIUS

92

ql-

............."--- _ _I i ^^.___

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V:, ] I'

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(b) 90° FROM INLET CENTERLINE

FIGURE 23. NORMALIZED SPECTRA OF DC-10-401JT9D-59A INFLIGHT JET-PLUS-CORE NOISE AT 45.7-METERRADIUS

i

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z'°°lo(_/fpe_,k)

(b) 90° FROM INLET CENTgRLINE

FIGURE 24. NORMALIZED SPECTRAOF DC-9-30/JTBD-109 INFLIGHT CORE NOISE AT 45.7METERRADIUS

96

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(a) 50° FROM INLET CENTV.RLINE

o

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(b) 90 u FROM INLET CENTERLINE

m..._' FIGURE 26. NORMALIZED SPECTRA OF DC-10-401JTgD-SgA INFLIGHT CORE NOISE AT 45.7-METER__;.. RADIUS

' 99

nnaial.,_- -- i 4 • i _

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FIGURE 30. JET/CORE AND TURBOMACHINEFIY STA'TIC NOISE SEPARATION FOR THE

JT8D-109. AT 70 DEGFIEES, 45.7-M POLAFI RADIUS

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(a) JTSD1U9 FREQUENCY SPECTRUMI

t

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:;_ FHEUUI:NCY, kiltE_,.

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_! FIGURE 32. IDENTIFICATION OF TURBINE NOISE IN STATIC TURBOMACHINERY NOISE LEVELS

I It)(_'............................ I i

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FICURE 37. JET/CORE AND "FURBOMACHINERY FLYOVER NOISE SEPARATION FORTHE DC-10-40/JTgD59Ao AT 13(11DEGREES, 45.7-M POLAR RADIUS

!

111 i

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i

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FIGURE 39. FAN EXHAUST AND TURBINE FLYOVER NOISE SEPARATION FOR THEDC-10-40/JT9D-59A, AT 130 DEGREES, 45.7-M POLAR RADIUS

113

, =, i l ! , l II .........

O0000002-TSB02

(a) N1/_/f/ = 6456.0 RPM ALTITUDE 112.8M

C=_ ( 6 de

_, .,_ _._ F-LIGHT

• /"/::: m> O...I

_ t I I 1 I I I I I I I, I , I _i, ;> 20 40 60 80 100 120 140 1

_! _ (blIN1/vt0 = 6553.0 RPM 31.5 M

i

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_ o \ !4: , ']

I1!

':: I I [ I I I I I l, I I I I I [20 40 60 80 100 120 140 160

ANGLE FROM iNLET CENTERLINE (DEGREER);"

FIGURE40. cOMPARISONOF FLIGHT AND STATIC-PROJECTEDPNLTS FOR THEDC-9-30/JT8D-109

114

O0000002-TSB03

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15PNdB

//"_----STATICt

II

I FLIGHTZI

> II.U-J If4_

0Z

I.U

__> 20 40 60 80 100 120 140 160I,,Ur,,,)

I,,I,I l ........

=.. ALTITUDE 152.4M(b} N1/_/0 = 3063.0 RPM /,.,,,-,=,._

5 PNdBLu / /I:I:m _ FLIGHT /o -.. .., _ -=z \0

\

., _ STATIC

m

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ANGLE FROM INL_:T CENTC:RLINE (DEGREES)

FIGURE 42. COMPARISON OF FLIGHT AND STATIC-CORRECTED PNLTS FOR THE DC-10-10/CF66,")

11r_

O0000002-TSB05

°":-7, " ' -g.i,l.l _

i _ <" <"li: l::l_w

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(hi NI/_/O = 3234.0 RPM ALTITUDE 347.5 M

S

I /" %%

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I, I I I I I 1 I .... 1 1 1 i l J40 _ e0 100 120 140 iS0

ANGLEFROMINLETCENTERLINE(DEGRI_EE$)

FIGURE 4_o COMPARISON OF: FLIGHT AND S_i'ATIC-CORRECTED PNLTS FOR THE DC-10-40/JTgD59A.

119

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r I 1, " !,! I '1 I ! ,, I_.......I

122

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123

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l I ' , I . J [ £ I , ___I__._50 80 125 200 315 500 800 1250 2000 31 bO boog H000

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FIGURE 64. COMPARISON OF DC-9-30/JT8D.109 SPECTRA AT DIFFERENT MICROPHONE LOCATIONSADJUSTED TO A COMMON APPROACH ALTITUDE

138

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t 13-OCTAVE-HAND CIENTE H FREEIUENCY, Hz

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139

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a)TEST ALTITUDE

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/I I I I I I I I I J

50 80 125 200 315 500 800 1250 2000 3150 5000 8000.-

1/3-OCTAVE.BAND CENTER FREQUENCY, Hz

=_ I lo_6 \",,uJ _

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O¢_ SYMBOL FLT RUN MIC MIC LOC ( ) ANG (m) (m)RPM

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n _ 212 45 1 C6 3482.5 90° 476,7 476.7

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1/3-OCTAVE-BANDCENTER FREQUENCY, Ht

FIGURE 66. COMPARISON OF DC-10-40/Jl"9b-59A SPECTRA AT DIFFERENT MICROPHONE LOCATIONSADJUSTED TO A COMMON TAKEOFF ALTITUDE

140

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1/3 ()(:lAVE HAND CENI L H FRt.(JUENCY (H.,,)

:" FIGURE 69. EXCESS-ATTENUATION COEFFICIENTS MEASURED AT OVERHEAD DURING TAKEOFF

143

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152

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1 , I _ I II +' !

========================: __++ = ++:::_: _ . !.................... ,

' , .......... :.........................................i::::::i:::::..........:+:'+-+::=:+_i, ...... ++_........ +I.......................... +, +_..........-- +iii "- " I

O0000002-TSE02

'.!

156

I II

O0000002-TSE03

157

'[ " ' t i

O0000002-TSE04

158

O0000002-TSE05

° !, 1"6

.-,r' _

r_

.... _ o,lo --c_. C_l o Cxl _o_c)

U. LU

: O_I-M I:> o4 1 _ o>l=-l-t,,),_.,ILl

_____ ........ 1 0 wu.

0 Un 0 U'_ 0 ,_OJ ,_- ,e- _0

u,n-

1 [,9

O0000002-TSE06

160

O0000002-TSE07

+ t t . t t t t +. I :

, ,+15'?+.4 lqE'rERS l,hVl+l+ FLt(+It'r GI_OUND MICROI'IIONE

0° FLAP DEFLECTI.ON

""'="==' 15 ° I,'LAP {)EFLECTION

[ -____l I ........ J. ....... --3.-...... M .... t ..... J ...... l

' (a) bO° FROM INLET CFNTERLINE

.................. +- 1._Y" _-_ ++._.-_-_-" _- _-,

SOUND PRESSURE _ --_-_-_LEVELS, dB

{

i__.t____J .... {.... x____i ......A___._.L..... t

(b) 90° FROM INLET CENTERLINE

m5 dB

" _L_I _ i t ..... I __ __L ......... I ,} I

63 125 250 500

I/3-OCTAVE-BAND CENTER FREOUENCY, llz

(C) 120 ° FRO_I INLET CENTERLINE

FIGURE 86. EFFECT OF FLAP SETTINGS ON DC-10+10/CFB-6DLOW-FREQUENCY FLYOVER NOISE

VII+ = 19B.1 MISEC, V. = 9.45 M/SEC (FLAP SETTINGS OF 0 AND 15 D_.GREES)

(

If,J_,.. 4 MI"/I'I._R_I,l".vl.',l, FI, I(]II'I' GROUND IdICRO]'IIONI'_

, 30 ° FLAP DEFLECTION

=="=="_ ==" 50 ° FLAP DEFLBCTION

(a) 60° FROM INLET CENTERLINE

I

II

SOUND I..---S" -- "-..___../_ _:-_ ....... .._..._PRESSURE

LEVELS

I I I ! i . I ....I . L

(b) 90° FROM INLET CENTERLINE

5 dBd.

1 1 , _L._j___I ...... l__ | 1 .

] 63 125 250 500

I/3-OCTAVE-BAND CENTER FREQUENCY, Hz

(c) 120 ° FROM INLET CENTERLINE

FIGURE B7. EFFECT OF FLAP SETTING ON DC-tO-101CF6-6DLOW-FREQUENCY FLYOVER NOISE.

Vip = 334.4 M/SEC, V,, = 94.5 M/SEC (FLAP SETTINGS OF 30 AND f)0 DEGREES.

_ 162

O0000002-TSE09

_- I I 1 , t I t -I _I I -"

ti: _ I_,t]_H-Mou}_D QROU_TDMI_ROPHoNt_

li o _Iflfl-IJI,l 1,]_|6JINE ............i,, . BIPlBOr_ - ¥_'i; M sd

'I+ ' ° + +.']_ ,;,,,.:t:TntlPl / 1 \'

++ . pp_g gpj+ . _,1.,

. <+> _/ •" ' +P_

p. -I0 I_i _

k.. -t_

!:., o \

-20 , _

k,+.,.

? -2 I I , |, , I J J_.. - .6 -1.2 -0.8 -0 4 0.0L,., 0.4*...................0.8 1.2 1.6

+_ _Olo(tltpep,_)

(a) DC-9-30/JT8D.109 CORE NOISE

o FIJUSIt-MOIrI_I_IIGItOI_ ltIOltOPItOI_

M/SI_

PJCl_IO'_]_ x ' 268.20 SPBO_RUM_ / _'"-. • i 241.4

(z'ef. 20) "_t:_ _'+,., 0 : 211.8

-5 / 4+ +'_ "\. /_ 192.6

set, - PEAKSpt, // I/ _ \'\. I

(+) i/iI o,, ,.10 /ii/" -1_ /'//

/-20 /

-25 + _ t J I L ..... 1..........I.........J ..........I"1.2 "0.8 "004 0.0 0.4 O.e 1.2 1,6

_lo(tlt_e_)

(b) DC-10A0/JTgD-.gA CORE NOOSE

t. FIGURE 88. COMPARISON OF MEASURED AND ANOPP PREDICTED COR_-NOISE SPECTRAl. SHAPESFOR DC.9.30/JTSD.109 AND DC.10-40/JTgD-59A AT 45,7-METER RADIUS AND 76,2M/SEC

I AIRCRAFT VELOCITY

................ 'i! % . 1 1 J' I ............................. +_+ --+.............................................. -+==++-+............... i_ ............ ._J+..................... , +.._+ _I ...................... I+_ -_.......m+-

O0000002-TBE _0

O MEASUREDo

.... mPREDICTION (re[. 20)

O ¢, th _p.-4 o R -.

C_ £-#

Fd "-

..fl O "" ..

,,t2

-I(, L I t............. -I -_L ...... __A ....... _-- ......... I20 40 60 _L,b 100 120 140 l&)

ANGLE FROH INLET, DEG _'

(a) Vj_ = 489.2 HISEC AND V - 90.8 HISECa

J

q-4 ¢ 0 0 ""0 .....

0 _

!

°I_ L........A...... I__.... L..... ._t...... -I...... t .......J20 40 60 BO 100 120 140 160

_4_ ANGLE FROM INLET, DEG

m Vjp - 93.3 M/SEC(b) = 446.5 M/sgc AND Va

o

0

-12 o

-I_; ......--J.... _i___L .......--J---.......I t J20 40 60 80 100 12o 140 16o

ANGLE FROH INLET, DEG

(c) Vjp 391.7 M/SEC AND Va 90.2 H/SEC

FIGURE 89. COMPARISON OF MEASURED AND ANOP_ PREDICTED JET.NOISE REDUCTIONS FORDC-9.30/JTBD-J0g IN FLIGHT AT 45.7.METER RADIUS (CONTINUED)

164

lib

O0000002-TS E11

.... I l.qtt:lJ}C!'lON ir|,I,;.til)

-4 ,%" 12,- . (._1

,'t

0

I1_¢'

, #-0 40 60 .. 100 120 140 150

ANGLE FROM tNI,ET, Di,',G

, Vjp = 90.5 M/SE( l(d) = 373.4 MISEC AND Vnca,1:1

•_ -4 o o 0-- 6 o

m

_ •r,_ -12

t

4J "16 _- I .... L....... -L....... _ .......1 ....... _[..... l

20 40 60 SO 100 120 140 160O0.r-I

ANGLE FROM INLr-T, DEGt_

_ (e) Vjp = 334.7 M/SEC AND Va = 89.6 M/SEC

0 -

O D O "1_.-._.

OO

-17

-16 ..... J--..... /_-- .[ ....... 1 1 . . t ......20 40 60 e_r, 100 l;ZO 140 lt,.

ANGLE FROM !NLET, i)EG

(f) V.pj = 321._, M/SECANDV = 78.o M/SEe;

FIGURE 8g. COMPARISON 01:: MEASURED AND ANOPP PREDICTED JET-NOISE REDUCTIONS FORDC-g-30/JTSD-109 IN FLIGHT AT 45.7-METER RADIUS

165

! _ " "............-" ;L..............."-'......................................._............................'..................u'OOOOOO2-TSE'""

0 MIEAI_URED--

0 _ -_- P_EDIC,TION (REF 20)

•- ..Q__..oC) O o

=I_. 0

-10 =.- I.... I I , I I I oI20 40 00 80 100 120 140 1(_0 _"'

ANGLE FROM INLET, DEC

(a} Vip = 502.9 M/SEC AND V. _ 98,B M/SEC

m"O 0 -

J _._0 0 0 O0 o

°_ -4 0

0 -12 _)II-Z

-1B _ .I . I _. __L._ _L_ I . [ . Ji. "_ 20 40 60 80 100 120 140 160, =L

ANGLE FROM INLET, DEG

O (b) Vlp = 493.8 M/SEC AND Va = 103.0 M/SEC

0

0 0 0 o 0 0 0

-8

-I_- E)

-tel _ ..... l . 1 __.L ..... ,L...... ,L..... I20 40 60 80 100 t20 140 160

ANGLE FROM INLET, DEG

(c) Vip = 480.0 M/SEC AND Va _ 101.6 M/SEC

FIGURE gO. COMPARISON OF MEASURED AND ANOPP PREDICTED JETNOISE REDUCTIONS FORDC-10-10tJT9D59A IN FLIGHT AT 45.7.METER RADIUS

166

II

O0000002-TSE 13

0 _ MEASURED

--_--,w"_-('_ 0 0 O O -- PRE_ICTIQN (REF _.O)

''_- .,_. C;)

-IP, O

.1020 .... I L I I I _L..... J, 40 60 80 100 120 140 1t30- ANGLE FROM INLET, DEG

. , (d) Vlp = 452.6 M/$EC AND Vu _ 98.5 M/_EC

__1 _ -4 " '_ "'_*-"-.-_ o o

'_'_: _ -12Lo O. I-.

z -16 ...... _ _ _L...... J ....... 1...... _l_ ___i __._.J' _- 20 40 60 80 100 120 140 160,., _J

g,,' _ ANGLE FROM INLET, DEG ,

O (e) Vlp = 435.8 M/$EC AND V = 96.6 M/SEC

, -4_- 0 O

' _ -8 - _' _'_ "-_

, 12O

,_.._..-.: -16 ! I 1 I I I J20 40 60 80 100 120 140 1_i0

ANGLE FROM INLET. DEG

,. (f) Vlp = 426.7 M/SEC AND Va _- 96.0 M/SEC

FIGURE 90. COMPARISON OF MEASURED AND ANOPP PREDICTED JET-NOISE REDUCTIONS FO_' DC10401JT9D-5gA IN FLIGHT AT 45.7.METER RADIUS (CONTINUED)

JJL__ - ,' t ' "

I I 1_ _' t I !, , II

Vjp

"_ r . Hlfil:r

I _ _'_

.[,(} _-. /, . VI7_' ,

"" ""V ''"_,__ _<',,. . -'i PRtIDICTED

-,o _ SPECTRUM

(ref. 20)

-._5,- ! 1 ......_u______X........ 1........ ',-1.6 -I. _ -O,_ -0,4 O.O O.d O._ t.P 1.'f-

(a) 50° FROM INLET CENTERLINE

-5 VII'

I * Mls_:c

A . 48,a.._

--I 0 _ * 44b. 5

v w/" "_v_\\

- / _TO '"

/

-25 - / _

/ _ PREDICTED /"-._o - SPECTRUM

(ref. 20)

-_5 _. ---L _1.... I , __L .. I ; i !. t-t,g -1,2 -0.8 -O,,l 0,0 (.;,4 ,',_ 1,? 1,t_

{,,!b°glO _lp-Va

(b) 90 ° FROM INLET CENTERLIN5

FIGURE 91. COMPARISONSOF MEASURED AND ANOPP PREDICTED JEI'-NOISE SPECTRAL SHAPESFOR DC4-30/JTSD-109 AT 45.7-METER RADIUS (CONTINUED)

168

O0000002-TSF01

f: <. .

' ' '- , ,,_I!:i I I_o ,,-i i

_I.I,I:: /,, ..._,,,_,_.'___ <.5 _ __,!; / @,L'_.. . g -,

__ "" -" 2

• I

--- _=

' t .............I I I L ..............1im

u_ (D tt_ 0 tt_ 0 i.'_I ,,e-. ',_ 0,I 0,,I l_h I_ m

I I I I I I _"

llp '"ldSVO - '1_J

169

! , , I li .. .... ,....................l I ........i . .

O0000002-TSF02

1 " I i, _, I I I I ',' i

,,,6 Viv

-I0 = V- &_;t+_

,p_ ,.,,. __ # _z,6

-,5 /_ o \ q_ +z6,1

+8.z / _ _,o.g

o_ ._o / . :Z'R_DIO"eZD,_ \' _ SPECTRUM

-_=- (ref..20) _,_\\ Iltg '\-_o- ,_ \,

-3S -- I ...... I , I I L , J ,. I _J ' J .... I

-t .it -0,B -0.4 O.O 0.4 0.B I .Z 1.6 2.0 2.4

-+:+ (a) 50° FROM INLET CENTERLINE

,'. VjR

#,_w,+,,m,"w'+_L v+ _,,.s_-" _ .. '_\ O-,,.sz.B

-_5 /_+ '++j.",, + ,,_.s

' ++ /\o %?\ o+,o,:+ _ -m ./' _ PP,,E])IO+]_D "_i\

_,, / sPzcmzN, %_\

++, _' =.+o. (,.,.._o), ,_=+o:) .\\ . +-3S J I I J I _

+ -1 ,Z -0,8 -o,,_ O,0. 0,4 o,8 ! ,2. 1,6 ;z,o 2,¢

(b) 90° FROM INLET CENTERLINE

FIGURE 92. COMPARISON OF MEASURED AND ANOPP PREDICTED JETNOISE SPECTRAL SHAPES FORDC-10-40/Ji"9D-59A AT 45.7-ME_'ER RADIUS

170

, + [ +.... < . I ......... , ........... -+, . . =+.--,,--_,_ . . J J ........ • ..... i

O0000002-TSF03

• _ _,_o ,,

- ,_

..,.j¢_

/ a_-/' _ "_

• _ _"

/ __ --_.]i / _ a-w

i ./ 'I_

• 0_:

1.1,1

I

t............_L..........I ........._...... .L..............Iz_ C) ur_ 0 ur_ 0 ur_I q- _ ¢_1 ¢_1 I_ I_i I I I I

I _P "ldSVO - "ldS

171.... •............ '_ .... , _,'._.;_.... _ ... " _...... i .......... "...... -,...... ,

O0000002-TSF04

i! ,, , t t I I ', I

t l >t ' ' )

g. , , 0

I .-/ i ......I- ,o"

(.i_ i---_ -- 7<> ul W

. _ =. __.,.U

_ o .met

,. ., _ ' <_<,_1=-.>_ -_>:

-__ o . _n- o 5 nro

d_

{- i,! i ,. i ii _ ooZZ

; l,i. _ IllI'- II.

i - 0,_ m

-Oi==

i ,= g8P "13A3"1 _uns"S31dd CiNnOS "'n,.

oli.

O0000002-TSF06

! I I" : i I I I I

' j _t e° --

- 7;'#.\ -.

,J//" I J _

.. _ _.,=I

1.61

_ _"'_LED.

- _ " ', _ I- --._.. _u _ _ \ _ _ OZ_

_ r, I "".'I} _ " O_

E_J U

.. _ 0 _'_l'u

" -e--_ _z_

BP '"13A33 _l:InSSg_d ONnOS

E

17,1

'! " _ _._ L_. .. _..i " _................. "• _"- TSFO" ...................... 00000002

: I I" " • '

177

_" " " _ ,1' i ",,.._,--_,. ,

O0000002-TSFIO

r!! , _,z I :' I I I I _,, I

FIGURE 99. COMPARISON OF THE EFFECTS OF FORWARD MOTION ON FAN BHOADBAND NOISE

LEVELS WITH PREDICTED EFFECTS OF CONVECTIVE AMPLIFICATION

O0000002-TSF11

O0000002-TSF12

180

' t /

O0000002-TSF13

'I _ I I' ,' l I I I " I

181

' ' 1 I

O0000002-TSF14

: ., ,"

,. ,: ..... ....... , _" 1....... i l " .......

00000002-TSG01

183

............ i ........................... ,

00000002-TSG02

tiP 1_A3"1 3NO1 "IV.I.N]IAIVLINn..I NV=I

' IB4

._: ........ nl I " II in ii II

00000002-TSG03

(::4

_"_ FAN FUNDAMENTAL TONE20 "

(a) INLET O DC.10.10/CF6.6D

Z_ DC-10-40/JT9D-59Af_

, ° 10

i '

_ o

| ,., ca , i ,. i I I I I Iit.

i: _ 20 " (b) EXHAUST

i •

n i ,,i

a i I i i i i l l," f,

, " 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4

i _ FAN ROTOR TIP MACH NUMBER

i : FIGURE 106. STATIC_TO-FLIGHT CORRECTION FOR THE EFFECTS OF NOISE GENERATION ON FAN FUNDAMENTALTONE FOR DC-10-10/CF_6D AND DC-10-40/JT9Do59A AIRPLANE CONFIGURATIONS

185

!,

00000002-TSG04

i.r

:COc:_ - 0 m

r,:, £I -

I:: glz.- 8 -_,_ _ ce,-

_,"! LB- 0

i:,' -'-...j __ _o_ 'a,, (J '_

I: ,Zr , t_: . ., z&

• W (3

I! ''1 I' ._- rr_wI - _ cc _,,,

'_' _:1- 0 r" 0 0

- _ // _i_i _4- ..=: _ _ ,,.

w _oZ_

C_ _Zb- -- ::,- _Dw

•_ u. o:

I: .... I 1 _ 0 I--"_

9 _zO

I , I r , _ _ OZU-

:m uJ

///"'_ ,:Ic-,-I _ z u_ _ /_, _ 0 ._. '__. _, __z_

_ _ __ z 00o

!i" BP "1.3A3"I31dns's3Bd QNNOS

00000002-TSG05

In7

|......... i' i, i ....... - .......... " -,

00000002-TSG06

1 l i !,,. l I I I l ,, l I l I I I20 40 60 80 100 120 140 160

=.F-=_. ANGLE FROM INLET CENTERLINE (DEGREES)

i ' FIGURE109. COMPARISON OF DC10-10 FLIGHT AND CF6-6D STATIC-CORRECIED PNLT%. CORRECTED FOR THE EFFECTS OF FORWARD MOTION, PROPAGATION, ANL

! ,,,. ENGINE INSTALLATION. i

• ! I t I

...... :..... * ......... i' ,_ i ..... '_ ,

00000002-TSG07

I!: In) N1/_/ll "- 2364 RPM ALTITUDE 120.4Mi

' "- _ 0gT

i.

.:_!, --

_ I I I I I I I I I I I I I [ 1

l:_i.: '_ 20 40 60 80 100 120 140 160

i:: L.i

Q.

-[ (b) N1/%/0 = 3234 RPM ALTITUDE 342.5MC_IJJ |I-.

!!,. _ 5PNdB'- J___ _O --

:, Z

O .ti_' P":,. STATIC-CORRECTED

_ /,_- \- -FLIGHT _/ i"" I 1 I I I I _ 1 l I I I 1 l I,, ,' 20 40 60 80 100 120 140 160

ANGLE FROM INLET CENTERLINE (DEGREES)

." FIGURE 110. COMPARISON OF DC-10-40 FLIGHT AND JT9D59A STATIC-CORRECTED PNLT'S:, CORRECTED FOR THE EFFECTS OF FORWARD MOTION, PROPAGATION, AND

ENGINE INSTALLATION.

! , _ J,-., , _. J, , . ! . , ,....

00000002-TSG08

" _ I i, I i i ' , ,

II ,/f" ql- -" li:li:

li ,,. % lit --_ I.I,I,i-'0 "__ _ I-_:II \, _j _ _ u_=='- .... :'7 Ic'i _"

_ _ .. ..... Id t_ -'I _"< , -'"'"....% _I_ o_

_ .% I_ _:--- ,..i/ , , Ji o°_=_

•_Z ll-

_ .- U/" _i --i _ =:_

,Y :: _ mNe_

-_ Y Je> oz_L8 _ n" <( W

-_ It 7e 5 4-..o,,_- _ ,",) 1o 7,, F-:._._

i < ,,tt ..ot-=w a..

_z_

I i..-<,,""r _"o

o >

:- / /<_ o, 41 .-_oP 1_ /.\,_ I© ,-:-.o_,<.>z,_

I:} l::l ,.,ib _ _o_ I I k Iii i_.z l.l.ii i 5 _ II / I l"4 _ 0<)

-o. _-o "311 °< -t"- ":__ = <_ ..... _ oo___F_._- .- -I I ill I _ n'i.._

,----=.--,,44",,' _ '"_ zi I'%,',' I 1 'o =I I"f

BP "I3A3q 31:InS_3_dONnOS

•l . I'I(II

............ . .._, t . I i ..... i ..... "

00000002-TSG09

"i lit) NIt' ,_ 54IiG RPM ALTITUDE 112.RM

;i, ' 6 PNdB

ir"

)7,. _

t: d

W

_,. e I_, o IZ

{,: _ I i I I I I 1 I I I I 1 I 1 i:;¢": I,,l,1 ' ' ' ' '

t_,, _ 20 40 60 80 100 120 140 160

_,, re

),, e,, T (b) NI/%/tJ = 6553.0 RPM ALTITUDE 731.5MillI-..

° Zi, U,I

i, ut FLIGHT, Z

i.

' / r STA11C-CORRECTED_ _ -

//

1 I I 1 1 1 I 1. 1 _1 1 I l l 120 40 60 80 100 120 140 160

'. ANGLE FROM INLET CENTERLINE (DEGREES)

FIGURE 113. COMPARISON OF DC-930 FLIGHT AND ,ITSD-109 STATICPROJECTED SPL SPECTRA" CORRECTED FOR INSTALLATION PROPAGATION AND CONVECTION EFFECTS,' DURING A 112.8-METER (370-FOOT) LEVEL FLYOVER.

SPEED - 5456.0 RPM.I el',)

, . l _. i i /

",........ ' .......................... 00000002-TSG 1"1

'lJ.

00000002-TSG12

I _.]4

j ,i , I i_.., , ". ............. J' i .....*. _ , -,

00000002-TSGI3

I

1 ' I I ' L I I ! ' | 7