NVH-Part-I-噪音、振動(dòng)、平順性

Automotive

Noise,Vibration&Harshness

1VehicleAttributesVehicleDynamicsNVHDurabilityCrashworthinessWeight$

Noise:VibrationperceivedaudiblyandcharacterizedassensationsofpressurebytheearVibration:Perceivedtactuallyatvehicleoccupantinterfacepointsofsteeringcolumn,seats,etc.Harshness:Relatedtotransientnatureofvibrationandnoiseassociatedwithabrupttransitioninvehiclemotion.ItcouldbeperceivedbothtactuallyandaudiblyWhatisN,V,andHTimeVs.FrequencyDomainsAcousticTactileTactileExcitations

ExcitationsExcitationsTime(Sec)TactileorAcousticResponseResponsesvarywithtimeasvehicleoperatesunderloadsResponsesareusuallysteadystateandperiodicinnatureItisconvenienttoconsiderresponsesinfrequencydomainwhilepreservingthesignalcontentDesignForNVHIntroductiontoNVHDFNVHHeuristicsDFNVHProcessFlowandTargetCascadeDFNVHDesignProcessFundamentalsKeyDFNVHPrinciplesAirborneNVHRadiated/ShellNoiseTubeInlet/OutletNoiseImpactiveNoiseAirImpingementNoiseStructure-BorneNVHWindNoiseExample2002MercuryMountaineerCaseStudySummary5IntroductiontoNVH

WhatisNVH?

6Movementisvibration,andvibrationthatreachesthepassengercompartmentintherightfrequenciesisnoise.ThescienceofmanagingvibrationfrequenciesinautomobiledesigniscalledNVH-Noise,Vibration,andHarshness.Itisrelativelyeasytoreducenoiseandvibrationbyaddingweight,butinanerawhenfueleconomydemandsareforcingdesignerstolightenthecar,NVHengineersmusttrytomakethesamepartsstiffer,quieter,andlighter.

IntroductiontoNVH

7

Noise:

Typicallydenotesunwantedsound,hencetreatmentsarenormallytoeliminateorreduceVariationsaredetectedbyearCharacterizedbyfrequency,level&qualityMaybeUndesirable(Airborne)MaybeDesirable(PowerfulSoundingEngine)IntroductiontoNVH

VibrationAnoscillatingmotionaboutareferencepointwhichoccursatsomefrequencyorsetoffrequenciesMotionsensedbythebody(structure-borne)mainlyin0.5Hz-50HzrangeCharacterizedbyfrequency,levelanddirectionCustomerSensitivityLocationsaresteeringcolumn,seattrack,toeboard,andmirrors(visiblevibrations)8IntroductiontoNVH

HarshnessLow-frequency(25-100Hz)vibrationofthevehiclestructureand/orcomponentsFrequencyrangeoverlapswithvibrationbuthumanperceptionisdifferent.Perceivedtactilelyand/oraudiblyRough,gratingordiscordantsensation9IntroductiontoNVH

10

AirborneNoise:Kindofsoundmostpeoplethinkofasnoise,andtravelsthroughgaseousmediumslikeair.Somepeopleclassifyhumanvoiceasairbornenoise,butabetterexampleisthehumofyourcomputer,orairconditioner.Detectedbythehumanear,andmostlikelyimpossibletodetectwiththesenseoftouch.Treatment/Countermeasures:BarriersorAbsorbers

IntroductiontoNVH

Structure-borne:

Vibrationthatyoupredominately“feel”,likethedeepboomingbasssoundfromthecarradionexttoyouatastoplight.Thesearetypicallylowfrequencyvibrationsthatyourearmaybeabletohear,butyouprimarily“feel”Treatment/Countermeasure:DampingorIsolation11IntroductiontoNVH

12Barriers:Performsablockingfunctiontothepathoftheairbornenoise.Examples:Acloseddoor,backingonautomotivecarpet.Barrierperformanceisstronglycorrelatedtotheopeningsorairgapsthatexistafterthebarrierisemployed.Apartiallyopendoorislesseffectivebarrierthanatotallycloseddoor.Barrierperformanceisdependentonfrequency,andisbestusedtotreathighfrequencies.Ifnogapsexistwhenthebarrierisemployed,thenweightbecomesthedominantfactorincomparingbarriers.IntroductiontoNVH

Barriers:DesignParameters

Location(closetosource)Material(cost/weight)MassperUnitAreaNumberandThicknessofLayersNumberandSizeofHoles13IntroductiontoNVH

14Absorbers:Reducessoundbyabsorbingtheenergyofthesoundwaves,anddissipatingitasheat.Examples:headliner,andhoodinsulator.Typically,absorbersarerankedbytheabilitytoabsorbsoundthatotherwisewouldbereflectedoffitssurface.Goodabsorberdesignscontaincomplexgeometriesthattrapsoundwaves,andpreventreflectionbackintotheair.Absorberperformancevarieswithfrequency.IntroductiontoNVH

15Absorbers:DesignParametersAreaofabsorbingmaterial(largeaspossible)Typeofmaterial(cost/weight)Thickness(package/installation)IntroductiontoNVH

16Damping:DefinedasatreatmentofvibrationtoreducethemagnitudeoftargetedvibrationsDampingisimportantbecauseitdecreasesthesensitivityofthebodyatresonantfrequenciesVehicleSourcesofDampingare:Mastics,sounddeadeningmaterials,weather-strips/seals,tuneddampers,andbody/enginemountsIntroductiontoNVH

17Damping:DesignParametersDensity(lowaspossible)Stiffness(highaspossible)Thickness(dampingincreaseswiththesquareofthickness)FreesurfaceversusconstrainedlayerConstrainedlayerdampingismoreefficientthanfreesurfacedampingonaweightandpackagebasis,butisexpensive,andraisesassemblyissues.Note:Temperaturerangeofinterestisveryimportantbecausestiffnessanddampingpropertiesareverytemperaturesensitive

IntroductiontoNVH

18Isolation:Methodofdetachingorseparatingthevibrationfromanothersystemorbody.Bydefinition:doesnothingtoreducethemagnitudeofvibration,simplyuncouplesthevibrationfromthesystemyouareprotecting.Allisolationmaterialsperformdifferentlyatdifferentfrequencies,andifengineeredincorrectly,maymakeNVHproblemsworseinsteadofbetter.IntroductiontoNVH

19IsolationbyBushingsandMounts:

Excitationsaregenerallyappliedtocomponentssuchasengineorroadwheels.Theforcetothebodyistheproductofthemountstiffnessandthemountdeflection,thereforestronglydependentonthemountspringratesCompliant(softer)mountsareusuallydesirableforNVHandride,butareundesirableforhandling,durabilityandpackaging(moretravel/displacementspacerequired).Typically,theisolationrates(bodymount/enginemountstiffness)thatarefinallyselected,isaresultofthereconciliation(trade-off)ofmanyfactors.IntroductiontoNVH

“NVHisoverwhelminglyimportanttocustomers.Younever,evergetluckywithNVH.Thedifferencebetweengoodcarsandgreatcarsisfanaticalattentiontodetail.”RichardParry-Jones,11/9920IntroductiontoNVH

WhyDesignforNVH21

NVHimpactsCustomerSatisfactionNVHimpacts

warantteeNVHhasfinancialimpactIntroductiontoNVH

WhyDesignforNVH22SUSTAIN/BUILD65%85%59RelativeLeverageIMPROVEREVIEWMAINTAINOverallHandlingCupholdersExteriorStyling**NVH6.977%CorporateLeveragevs.CustomerSatisfactionNVHCustomerSatisfactionNeedsImprovementat3MIS*IntroductiontoNVH

WhyDesignforNVH23NVHCanBothDissatisfyandDelight+Performance+CustomerSatisfaction-PerformanceDissatisfiersHarleyMustangLexusLoudnessUnusualNoisesTGWSoundQualityTGRKANOModel+DegreeofAchievementBasicQuality(Inhibitors)PerformanceQuality(Attributes)-CustomerSatisfactionExcitingQuality(Surprise&Delight)AxleWhineWindNoiseIntroductiontoNVH

WhyDesignforNVHCustomersplaceahighvalueonNVHperformanceinvehiclesAbout1/3ofallProduct/QualityComplaintsareNVH-related24SummaryofCustomerImportanceIntroductiontoNVH

WhyDesignforNVHAbout1/5ofallWarrantycostsareNVH-relatedDealermayspendmanyhourstodeterminesourceofNVHproblemDealermayhavetorepairorrebuildpartsthathavenotlostfunctionbuthavebecomesourceofNVHissue.NVHcanprovidebothdissatisfactionanddelight25SummaryofCustomerImportance(continued)DesignForNVHIntroductiontoNVHDFNVHHeuristicsDFNVHProcessFlowandTargetCascadeDFNVHDesignProcessFundamentalsKeyDFNVHPrinciplesAirborneNVHRadiated/ShellNoiseTubeInlet/OutletNoiseImpactiveNoiseAirImpingementNoiseStructure-BorneNVHWindNoiseExample2002MercuryMountaineerCaseStudySummary26DesignForNVH

HeuristicsDesignthestructurewithgood"bones"IftheNVHproblemisinherenttothearchitecture,itwillbeverydifficulttotune

itout.Toremaincompetitive,determineandcontrolthekeystothearchitecturefromtheverybeginning.SetaggressiveNVHtargets,selectthebestpossiblearchitecturefromthebeginning,andstickwithit(additionalupfrontNVHresourcesarevaluableinvestmentsthatwillreturnahighyield)27DesignForNVH

Heuristics

CostrulesOncethearchitectureisselected,itwillbeverycostlytore-selectanotherarchitecture.Therefore,anybaddesignwillstayfor

alongtime28DesignForNVH

HeuristicsDon'tconfusethefunctioningofthepartsforthefunctioningofthesystem(JerryOlivieri,1992).WeneedtofollowSystemsEngineeringprinciplestodesignforNVH.Customerswillsee

functionsfromthesystem,butsounddesignsrequiresourabilitytodeveloprequirementsofthepartsbycascading

functionalrequirementsfromthesystem29DesignForNVHIntroductiontoNVHDFNVHHeuristicsDFNVHProcessFlowandTargetCascadeDFNVHDesignProcessFundamentalsKeyDFNVHPrinciplesAirborneNVHRadiated/ShellNoiseTubeInlet/OutletNoiseImpactiveNoiseAirImpingementNoiseStructure-BorneNVHWindNoiseExample2002MercuryMountaineerCaseStudySummary30DesignForNVH

ProcessFlowandTargetCascade

Duringtheearlystagesofavehicleprogram,manydesigntrade-offsmustbemadequicklywithoutdetailedinformation.

Forexample,onthebasisofeconomicsandtiming,powerplants(engines)whichareknowntobenoisyarechosen.Theprogramshouldrealizethatextraweightandcostwillberequiredinthesoundpackage.(HistoricalData)Ifaconvertibleistobeoffered,itshouldberealizedthatanumberofmeasuresmustbetakentostiffenthebodyintorsion,andmostlikelywillincludestiffeningtherockers.(ProgramAssumptions)31DesignForNVH

ProcessFlowandTargetCascade

32DesignForNVH

ProcessFlowandTargetCascade

33NoiseReductionStrategy:Targetsareevensetforthenoisereductioncapabilityofthesoundpackage.DesignForNVH

ProcessFlowandTargetCascade

34SystemsEngineering“V”andPDProcessTiming&IterateDefineReq’s

CascadeTargetsOptimizeVerify&OptimizeConfirmVehicle(VDS-P/TNVHetc)System(SDS-Force,Sensitivity,......)Subsystem(stiffness,....)ComponentsCDSWants/NeedsCustomerSatisfactionSIPACPPRSCKOCustomerJ1

DesignForNVH

ProcessFlowandTargetCascade

35Trade-OffLoopPerformIterationsUntilAssumptionsComparableSystem/Sub-SystemAssumptionsMcPhersonvs.SLA,etc.RequiresHardwareParametricModelVehicleAssumptionsFixedSLAorMcPhersonStrutSuspensionVehicleLevelTargetRangesSubjective(1-10)andObjectiveProgramSpecificWantsPALS(QFD,VOC,etc.)FunctionalImagesforSegment-R202PreliminaryTargetRangesFutureFunctionalAttributeTargetsObjectiveTargetRanges-VDSAffordableBusinessStructure(ABS)SISystem&Sub-SystemTargetsForceorP/FTargetsDeterminedwithParametricModelsComponentEndItemTargetsComponentResonantFrequencies,etc.DesignOptimizationCAEOptimizationHardwareDevelopmentPATrade-OffsFlowChartIsGrossArchitectureFeasible?DevelopmentDesignForNVH

ProcessFlowandTargetCascade

36NVHFunctionalAttributeSub-AttributesRoadP/TWindBrakeComp.S.Q.S&RPass-byNoise(Reg.)DesignForNVH

ProcessFlowandTargetCascade

37ConvertattributetargetstrategytoobjectivetargetsPOWERTRAINNVHIDLENVHACCELERATIONNVHCRUISENVHDECELERATIONNVHSTEERINGNVHAUTOMATICTRANS.SHIFTNVHTIP-IN/TIPOUTNVHTAKE-OFFDRIVEAWAYNVHENGINESTARTUP/SHUTOFFNVHTRANSIENTSNVHACCELERATIONWOTDesignForNVH

ProcessFlowandTargetCascade

38CUSTOMERPERCEIVEDP/TNVHAIRBORNENOISESTRUCTURE-BORNENOISEP/TRADIATEDNOISEAIRBORNENOISEREDUCTIONBODYACOUSTICSENSITIVTYMOUNTFORCESP/TVIBRATIONMOUNTDYNAMICSTIFFNESSAccelerationNVHTargetCascadeProcessFlowandTargetCascade39

NVHClassificationParametersOperatingCondition(idle,acceleration,cruiseonaroughroad,braking…)Phenomenon(boom,shake,noise…)thisisstronglyaffectedbythefrequencyofthenoiseandvibration.Source(powertrain,road,wind..etc)ClassifyingNVHproblemsprovidesaguidancefordesign,forexample,lowfrequencyproblemssuchasshake,historically,involvesmajorstructuralcomponentssuchascrossmembersandjoints.ProcessFlowandTargetCascade40

OperatingConditionNVHConcernsIdleShakeandboomduetoenginetorque.LuggingShakeandboomduetoenginetorque.WOTNoiseandvibrationduetoengine,exhaustvibration,andradiatednoise.Cruise(smoothroad)Shake,roughness,andboomduetotireandpowertrainimbalanceandtireforcevariation,Windnoise,TireNoiseCruise(roughroad)RoadnoiseandshakeTip-in"Moan"duetopowertrainbending.BrakingSquealduetobrakestick-slip.ProcessFlowandTargetCascade41Thecustomer’sexperienceofNVHproblemsinvolvestwofactors,1)thevehicleoperatingconditions,suchasbrakingorWOT,and2)theverysubjectiveresponsessuchasboom,growl,andgroan.Itiscriticalthatobjectiveandsubjectiveratingsbecorrelatedsothecustomerconcernscanbedirectlyrelatedtoobjectivemeasures.Thisrequiressubjective-objectivecorrelationstudiescomparingcustomerratingsandobjectivevibrationmeasurements.ProcessFlowandTargetCascade42NVHAspectSubjectiveResponseBoomLowfrequencysound20-100hz.DroneLargeamplitudepuretoneintheregion100-200hz

GrowlModulatedlow/mediumfrequencybroadbandnoise100-1000hz

GroanTransientbroadbandnoisewithnoticeabletimevariationandtonecontent,50-250hz

MoanAsoundinthe80to200Hzrange,frequentlyconsistingofoneortwotonesSqueakHighpitchedbroadbandtransientnoise.WhineMid-frequencytohighfrequencypuretone(possiblywithharmonics),200-2000hzProcessFlowandTargetCascade43

SummaryNoisereductiontargetsshouldbesetforimportantoperatingconditionssuchasWOT(wideopenthrottle).Noisereductiontargetsmustbesetfortheradiatedsoundfromthevarioussources.Thesoundpackagemustbeoptimizedforbarriertransmissibilityandinteriorabsorption.ClassifyingNVHproblemsprovidesguidancefordesignandameanstocommunicationamongengineers.DesignForNVHIntroductiontoNVHDFNVHHeuristicsProcessFlowandTargetCascadeDFNVHDesignProcessFundamentalsKeyDFNVHPrinciplesAirborneNVHRadiated/ShellNoiseTubeInlet/OutletNoiseImpactiveNoiseAirImpingementNoiseStructure-BorneNVHWindNoiseExample2002MercuryMountaineerCaseStudySummary44ProcessFundamentals

Source-Path-Responder45SensitivityExcitationResponseEngineFiringPulsesDriveshaftImbalanceRoughRoadTireImbalanceSpeedBumpGearMeshingBody-ShapeInducedVorticesExcitationSourceExamples:ProcessFundamentals

Source-Path-Responder46SensitivityExcitationResponseTendencyofthepathtotransmitenergyfromthesourcetotheresponder,commonlyreferredtoasthetransferfunctionofthesystemSensitivity:47ProcessFundamentals

Source-Path-ResponderExample:BodySensitivityTactilePointmobility(v/F)(Structuralvelocityinducedbyforce)AcousticAirborne(p/p)(Airbornesoundpressureinducedbypressurewaves)Structureborne(p/F)(Airbornesoundpressureinducedbyforce)F(N)V(mm/s)p(dB)ForceInputatDrivingPointVibrationVelocityatDrivingPointInteriorSoundPressureSTRUCTUREp(dB)p(dB)InteriorSoundPressureSTRUCTUREAirborneNoise48ProcessFundamentals

Source-Path-ResponderBodySensitivityDemonstrationPointMobilityTypicalPointMobilitySpectrumforCompliant&StiffStructuresPointMobility(V/F)MoreCompliantLessCompliantFrequency(f)50140ProcessFundamentals

Source-Path-Responder49Subjective(customerperception)S/WShake(vertical)S/WNibble(rotational)SeatTrack(non-specific)Objective(measurable)S/WShakeS/WNibbleSeatTrack(Triax)SpindleFore/AftTieRodLateralResponse:SensitivityExcitationResponseS/W=SteeringWheelProcessFundamentals

Source-Path-Responder50AirborneP/TNVHStructure-borneP/TNVHTailpipeIntakeOrificeEngineRadiatedSoundActiveEngineVibration(X,Y,Z)ActiveExhaustVibration(X,Y,Z)BodyAcousticAttenuation(dB)BodyAcousticAttenuation(dB)MountStiffness(N/mm)BodyAcousticSensitivityMountStiffness(N/mm)BodyAcousticSensitivityDriverRightEar(dBA)AirborneNVHStructure-borneNVHPowertrainNoiseModelProcessFundamentals

Source-Path-Responder51RoadNoise(P)ChassisForcestoBody(F)NPABody/FrameSensitivity(P/F)+SuspensionForceIsolation

Tire/WheelForcesSuspension/FrameModesSuspension/FrameDesignParametersTire/WheelModes&DesignParametersBodyModesBodyDesignParametersSub-structuringModalAnalysis(MA)MATire/RoadForceTransferFunction+RoadProfileRoadNoiseModelProcessFundamentals

Source-Path-Responder52DrivelineModelProcessFundamentals

SoundQuality53WhatisSoundQuality?Historically,NoiseControlmeantreducingsoundlevelFocuswasonmajorcontributors(P/T,Road,WindNoise)SoundhasmultipleattributesthataffectcustomerperceptionAllvehiclesoundscaninfluencecustomersatisfaction (e.g.,componentSoundQuality)NoiseControlnolongermeanssimplyreducingdBlevelsProcessFundamentals

SoundQuality54WhySoundQuality?Generallynottiedtoanywarrantyissue

ImportanttoCustomerSatisfaction -Purchaseexperience(doorclosing) -Ownershipexperience(powertrain/exhaust)Astrongindicatorofvehiclecraftsmanship -Brandimage(powertrain)ProcessFundamentals

SoundQuality55TheSoundQualityProcess1.Measurement(recording)2.Subjectiveevaluation(listeningstudies)Actualorsurrogatecustomers3.ObjectiveanalysisSoundqualityMetrics4.Subjective/Objectivecorrelation5.ComponentdesignforsoundqualityProcessFundamentals

SoundQuality56BinauralAcoustic“Heads”StereoSoundRecordingrepresentingsoundwaveinteractionw/humantorsoProcessFundamentals

SoundQuality57SoundQualityListeningRoomUsedforCustomerListeningClinics.ProcessFundamentals

SoundQuality58PoorSoundQualityGoodSoundQualityProcessFundamentals

SoundQuality59QuantifyingDoorClosingSoundQuality1.SoundLevel(Loudness)2.FrequencyContent(Sharpness)3.TemporalBehavior

ProcessFundamentals

SoundQuality60WhatMakesAGoodDoorClosingSound?

GoodSound

PoorSound

Quiet LoudLowFrequency HighFrequency(Solid) (Tinny,Cheap)OneImpact RingsOn(Bell)NoExtraneousNoise Rattles,Chirps,etc. ProcessFundamentals

SoundQuality61Example:QualifyingDoorClosingSoundQualityGoodBadLevel(dBa)(color)Frequency(Hz)(y-axis)Time(sec.)(x-axis)ProcessFundamentals

SoundQuality62DesignforSoundQualityDoorClosingExamplePerceivedSoundStructure-borneAirborneSealTransLossLatchForcesStr.ComplianceInertiaSpringRatesMaterialRadiatedSnd.ProcessFundamentals

SoundQuality63ConclusionsSoundQualityiscriticaltoCustomerSatisfactionUnderstandsoundcharacteristicsthatgovernperceptionUpfrontimplementationisthebiggestchallengeUsecommodityapproachtocomponentsoundqualityGenerictargets,supplierawareness,benchtestsDesignForNVHIntroductiontoNVHDFNVHHeuristicsProcessFlowandTargetCascadeDFNVHDesignProcessFundamentalsKeyDFNVHPrinciplesAirborneNVHRadiated/ShellNoiseTubeInlet/OutletNoiseImpactiveNoiseAirImpingementNoiseStructure-BorneNVHWindNoiseExample2002MercuryMountaineerCaseStudySummary64NVHDesignPrinciplesDynamicSystemNVHModel: SourceXPath=ResponseAlwaysworkonsourcesfirstReducethelevelofALL

sourcesbyusingquietcommoditiesPathisaffectedbysystemarchitecture.Needtoselectthebestarchitectureintheearlydesignphase.EngineerthepathsineachapplicationtotailorthesoundlevelOnlyresorttotuninginthelatestageofdesign6566NVHDesignPrinciplesTubeInlet/OutletNoiseExcitationSource,EnergyInputStructureSensitivityCustomerAirborneNVHStructure-borneNVHAirImpingementNoiseSourcePathResponderImpactiveNoiseRadiated/ShellNoiseAcousticAttenuationAcousticAttenuationAcousticAttenuationAcousticAttenuationEnvironmentSensitivityIsolationStiffnessIsolationDamping67NVHDesignPrinciplesTubeInlet/OutletNoiseExcitationSource,EnergyInputStructureSensitivityCustomerAirborneNVHStructure-borneNVHAirImpingementNoiseSourcePathResponderImpactiveNoiseRadiated/ShellNoiseAcousticAttenuationAcousticAttenuationAcousticAttenuationAcousticAttenuationEnvironmentSensitivityIsolationStiffnessIsolationDampingDesignPrinciples–AirborneNVH

Radiated/ShellNoiseMechanism:

Structuralsurfacevibrationimpartsmechanicalenergyintoadjacentacousticfluidintheformofpressurewavesatsamefrequencycontentasthesurfacevibration.Thesewavespropagatethroughthefluidmediumtothelistener.Examples:powertrainradiatednoise,exhaustpipe/mufflerradiatednoiseDesignprinciple(s):Minimizethevibrationlevelonthesurfaceofthestructure68DesignPrinciples–AirborneNVHRadiated/ShellNoiseDesignAction(s):Stiffen:

Addribbing,increasegaugethickness,changematerialtoonewithhigherelasticmodulus,addinternalstructuralsupportMinimizesurfacearea:

RoundsurfacesDamping:

Applymasticadhesivestosurface,makesurfacesoutofheavyrubberMassloading:

Addnon-structuralmasstoreducevibrationamplitude---(Onlyasalastresort)69DesignPrinciples–AirborneNVH

TubeInlet/OutletAirflowNoiseMechanism:Pressurewavesareproducedinatubefilledwithmovingfluidbyoscillating(open/closed)orifices.Thesewavespropagatedowntubeandemanatefromtheinletoroutlettothelistener.Examples:inductioninletnoise,exhausttailpipenoiseDesignprinciple(s):Reducetheresistanceinthefluidflow70DesignPrinciples–AirborneNVH

TubeInlet/OutletAirflowNoiseDesignaction(s):MaketubesasstraightaspossibleIncludeanin-linesilencerelementwithsufficientvolumeLocateinlet/outletasfarawayfromcustomeraspossibleDesignforsymmetrical(equallength)branches71DesignPrinciples–AirborneNVH

TubeInlet/OutletAirflowNoise72V6IntakeManifoldsDesignPrinciples–AirborneNVH

ImpactiveNoiseMechanism:Twomechanicalsurfacescomingintocontactwitheachothercausesvibrationineachsurface,whichimpartsmechanicalenergyintoadjacentacousticfluidintheformofpressurewavesatthesamefrequencyasthesurfacevibration.

Thesewavespropagatethroughthefluidmediumtothelistener.

-Examples:Tireimpactnoise,doorclosingsound,powerdoorlocksoundPressureswavescausedbyairpumpinginandoutofvoidsbetweencontactingsurfaces

-Examples:Tireimpactnoise73DesignPrinciples–AirborneNVH

ImpactiveNoise74AirPumpingAirforcedinandoutofvoidsiscalled“airpumping”DesignPrinciples–AirborneNVH

ImpactiveNoiseDesignprinciple(s):ReducethestiffnessoftheimpactingsurfacesIncreasedampingofimpactingsurfacesDesignaction(s):Changematerialtoonewithmorecompliance,higherdampingManagementofmodalfrequencies,modeshapesofimpactingsurfaces(tiretreadpattern,tirecavityresonance)75DesignPrinciples–AirborneNVH

AirImpingementNoiseMechanism:Whenanobjectmovesthroughafluid,turbulenceiscreatedwhichcausesthefluidparticlestoimpacteachother.Theseimpactsproducepressurewavesinthefluidwhichpropagatetothelistener.Examples:enginecoolingfan,heaterblower,hairdryerDesignprinciple(s):Reducetheturbulenceinthefluidflow76DesignPrinciples–AirborneNVH

AirImpingementNoiseDesignaction(s):Designfanbladesasymmetrically,withcircumferentialringOptimizefandiameter,flowtoachievelowestbroadbandnoiseUsefanshroudtoguidetheincomingandoutgoingairflow7778NVHDesignPrinciplesTubeInlet/OutletNoiseExcitationSource,EnergyInputStructureSensitivityCustomerAirborneNVHStructure-borneNVHAirImpingementNoiseSourcePathResponderImpactiveNoiseRadiated/ShellNoiseAcousticAttenuationAcousticAttenuationAcousticAttenuationAcousticAttenuationEnvironmentSensitivityIsolationStiffnessIsolationDampingDesignPrinciples–AirborneNVH

AirborneNoisePathTreatment79NoiseReductionEngine

Compartment

AbsorptionBody&

InsulatorBlocking

(Panels)Pass-ThruSealing

(Components)Interior

AbsorptionDesignPrinciples–AirborneNVH

AirborneNoisePathTreatmentDesignprinciple(s):AbsorbnoisefromthesourceBlockthesourcenoisefromcominginAbsorbthenoiseafteritisinDesignaction(s):SurroundsourcewithabsorbingmaterialsMinimizenumberandsizeofpass-throughholesUseHigh-qualitysealsforpass-throughholesAddlayersofabsorptionandbarriermaterialsinnoisepathAdopttargetsetting/cascadingstrategy80DesignPrinciples–AirborneNVH

AirborneNoisePathTreatmentBarrierperformanceiscontrolledmainlybymass3dBimprovementrequires41%higherweightMasticorlaminatedsteelimproveslowfrequencySoftdecoupledlayers(10-30mm)absorbsoundPass-thrupenetrationsealsweakerthansteel81airabsorptionmaterials82NVHDesignPrinciplesTubeInlet/OutletNoiseExcitationSource,EnergyInputStructureSensitivityCustomerAirborneNVHStructure-borneNVHAirImpingementNoiseSourcePathResponderImpactiveNoiseRadiated/ShellNoiseAcousticAttenuationAcousticAttenuationAcousticAttenuationAcousticAttenuationEnvironmentSensitivityIsolationStiffnessIsolationDampingDesignPrinciples–AirborneNVH

AirborneNoiseResponderTreatmentDesignprinciple(s):AbsorbnoiseatlistenerBlocknoiseatlistenerBreakupofacousticwavepatternDesignaction(s):SurroundlistenerwithabsorbingmaterialsEarplugsDe