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“乘员不应该听到脚下的电池组和电驱动系统运行的声音，而车外的噪音仍然需要感知到。”Saha断言：“在某些时候，这些噪音将成为一项质量问题。”
他说：“看待这个问题的一种角度是，牵引电机或齿轮传动系统发出的噪音如果被客户在车内听到了，那就是问题。路噪和风噪可以在一定程度上掩盖来自EDU(传动系统)的噪声。能被掩盖自然是好的，但你能寄希望于非常糟糕的[路噪和风噪]来掩盖系统噪声，毕竟路噪或风噪太大，也容易让客户觉得这根本不是一辆精致的汽车。”
不断发展的仿真试验
Govindswamy指出，更精致的高端电动车通常在减少进入座舱内的路噪和风噪方面“做得非常好”，但有时也是以暴露高转速电机和齿轮系统的高频噪音为代价的。动力逆变器也会表现出10,000赫兹范围内的高频噪声。
“我们使用所谓的‘多体系统仿真’（对相互关联的多个运动部件如何相互作用的动态系统级分析）和有限元分析的组合，考虑了电磁力以及齿轮传动系统的作用力，从而可预测出噪声水平。FEV正在不断改进其预测结果的置信度和准确性，以确保能满足客户的目标。”Govindswamy说：“当我们导入第一个原型进入测试单元时，我们发现离我们需要达到的目标并不遥远。”
专家断言，仿真试验正在不断改进，但在关联性方面仍有许多工作要做。“我们却非常依赖仿真分析，但我认为许多新公司（汽车初创公司）有些过于信赖仿真结果。”Saha认为：“他们在开发到较晚阶段时才验证仿真结果，或者他们的仿真预测可能不完全正确。我们已经看到了根据测量结果来反调预测的例子。我无法理解他们是如何达到目标的。”
他指出，虽然那些正在进入电动车领域的传统主机厂也在使用预测性仿真模拟，但“他们有更强大的测量经验背景”，并在开发过程中能更早地验证他们的预测。
轻量化设计和仿真
电动卡车、大型公共设施和高性能电动车中的锂离子电池组有着惊人的载荷，这就需要车身工程师用轻量化材料方案来抵消这些重量，在某些情况下，这也导致了座舱层面的NVH问题。
尽可能减少额外的NVH处理装置和声学包的质量是一个重点。“这又回到了从源头上减少噪声的重要性。”Govindswamy说：“大量的仿真工作正在进行中，这是一个挑战。但这也教会了工程师们能更有效地使用更轻的声学材料。”
与汽车开发的所有领域一样，仿真试验越来越成为缓解NVH噪声的组成部分。“我把它看作是一个金字塔，顶端是目标定义签字，下面是大量的具体工作，以实现定义目标。”VI-grade公司产品管理高级主管DaveBogema说。该公司是NVH和车辆动力学工作的仿真工具制造商。NVH分析从桌面开始，工程师们使用最新的、功能越来越强的分析软件快速处理各种想法并剔除那些不可行的想法。下一步是主观评价，如果想让决策具有很高的置信度，就必须真正体验一下NVH状态。
“你可以从电脑界面上得到一定程度的答案。”Bogema说：“但电脑仿真并不能提供在物理模拟器上体验虚拟原型所带来的沉浸感和现实感的全部好处。”
由于物理领域的多样性和这些领域之间复杂的相互作用，预测由电机产生的声学噪音和振动是具有挑战性的。电磁学、热力学和振动声学分析需要以耦合的方式对电机产生的声学噪声进行精确预测。根据Ansys解决方案，准确预测声学噪声有四个基本要素：需要一个高保真仿真解决方案来说明所有涉及的物理学科；一个耦合所有不同的物理学元素的平台；为每个涉及的物理学参数设置和优化的设计能力，以及加速模拟的高性能算力。
还有车辆动力学，在许多方面与NVH密不可分，包括如何影响虚拟样车的评估过程和乘员对车辆精良性的感知等。物理仿真工具也在扩大，以满足电动车改进的各个方面。
“当你驾驶一辆车时，你能体会到周遭的一切。”VI-grade的Bogema说：“如果你在做乘坐舒适性评价，这是一种多感官的运动、振动和声音体验，把NVH和车辆动力学结合在一起，可以提供很好的重复性和管控力，这对提高整体置信度来说至关重要。”他的公司最近在2023年SAE噪声和振动会议上推出了新的紧凑型全频谱模拟器（FSS）。紧凑型FSS能够进行0.5Hz到20kHz的模拟，同时提供主要和次要驱动运动、振动和异响。虽然不是传统的六足式模拟器设计，但FSS的四条腿使它能够准确地再现，在坑洞、鹅卵石或任何其他表面行驶时发生的道路状态。它的振动器通过方向盘和座椅产生高频振动，此外还模拟有来自路面的运动。
VI-grade还提供了一个专用的紧凑型NVH驾驶模拟器，使工程师能够准确地调出汽车在NVH方面的感觉。它的座椅结构允许尝试一系列的虚拟座椅设计，而FSS需要改变座椅的物理形式。专用的NVH模拟器“可以立即改变座椅参数，感受座椅之间的差异”，Bogema指出。“他们是为不同的使用场景而设计的。”他说。FSS在很大程度上是针对乘坐舒适性课题的；而NVH版本则是为了精调设计的。
工程师们也意识到，他们可以在桌面软件上进行声音设计，相应地，模拟出不同的汽车声效。振动也是如此。“你真的需要在声音设计中考虑到车辆的整体运动吗？也许不是所有的时候。”Bogema说。
定制版NVH组件
提高车辆精良性的门槛并不是电动汽车的专利。专家们说，电动车和混合动力车正在推动新的设计和降低NVH的方法，包括那些仍然由内燃发动机汽车主导的产品领域。然而，他们也注意到，成本压力会使复杂的设计变得难以销售，除非其NVH性能十分出众。
全球领先的汽车NVH解决方案供应商Vibracoustic最近推出的用于空气悬架供气装置（ASU）的新型可调支架就是一个注重NVH的例子。简单而复杂的新ASU，如附图所示，具有一个塑料底座（以前是钢），以改善阻尼性能，以及波纹管式橡胶衬套和防撞块。衬套的特殊材料特性恰好满足了所需的刚度水平，同时也对压缩机产生的径向和轴向振动提供避震。
据Vibracoustic称，新的安装支架比传统支架更轻、更坚固，并能在各个方向上就NVH性能进行调整，这是通常用于此类应用的螺旋弹簧所无法做到的。此外，波纹管式衬套设计允许在低应变水平上实现高位移，重现了弹簧的性能。该公司工程师称，橡胶材料还有助于将共振峰值保持在合理的范围内，因为橡胶化合物表现出的动态刚度峰值比螺旋弹簧低60%。
据FEV的Govindswamy介绍，未来电动车NVH技术和工程的关键是取得一种平衡：在不降低车辆续航能力的情况下满足客户的精细化期望。“如果你能保证电动马达的效率并接受稍高的噪音，使其对客户的影响最小化，这就是我们正在努力的挑战，而这要归结为系统优化。”
NVH软件模拟解决方案
在几十家提供NVH仿真软件工具的供应商中，有很多受SAE读者欢迎的产品：
Actran
作为HexagonAB的一部分，Actron是一种基于FE(有限元)的工具，用于对机械系统和部件的声学行为进行建模。其被广泛用于解决中频（400-1500Hz）范围内的NVH问题，这对电动汽车设计至关重要。作为一个"开放"的工具，它利用现有的FE和CFD仿真模型，用于研究电动汽车的传动和辅助系统（泵、压缩机）噪声源。例如，通用汽车工程师使用Actran来优化凯迪拉克Lyric电动车的噪音减震处理。
Altair
Ansys
AVL
Brüel&Kjr
DesktopNVH、SimSound、SourcePathContribution和VSound使工程师能够为任何配置的车辆设计和评估车内和车外声音。Insight+实现了NVH数据的全面体验，直接从CAE模型中创建声音，NVH工程师可以聆听体验。CAE模型数据可以与测试数据结合起来，创造一个身临其境的真实环境。
Dassault
广泛使用的标志性的SIMULIA套件为NVH工作提供了全面的仿真工具集。
Dewesoft
在以NVH为重点的工具中，声音质量测量工具很好地解决了以往按经验评估不同种类机器产生的声音如何被人耳感知的工作。该工具可帮助工程师确定声音是如何被感知的，并调校声音，并使其更容易被客户接受或更具吸引力。
Hexagon
该公司的RomaxSpectrum能够进行机电动力总成NVH仿真，并提供完整的、参数化的动力总成全系统建模，包括齿轮和轴承接触面。Romax套件提供与第三方CAE工具的接口，包括用于声学的Actran;用于多体仿真的Adams；用于电磁模拟的JMAG和Maxwell;用于FE建模的Nastran；用于整车NVH和声音质量的VI-grade。
SiemensDigitalIndustries西门子的Simcenter套件会继续增加NVH分析工具，这些工具受益于数字孪生法，可准确预测车辆内部和外部NVH性能。
Electrificationbringsnewbenchmarks,tools,andchallengestotheongoingbattlewithnoise,vibrationandharshness.NVHtestingatFEV’sAuburnHills,Michigan,techcenterusingHEADAcousticsdigitalartificialheadinstruments.Withtwoparallelanalog-to-digitalconverterstheHEADunitscovertheentireaudibledynamicrange.
Thecomplexscienceofanalyzingandabatingnoise,vibration,andharshnesshasentereda“newfrontier”astheindustrytransitionstoelectrifiedvehicles,expertsintheNVHfieldtellSAEMedia.Newdesignandengineeringchallengesatthecomponent,system,andfull-vehiclelevelscontinuetoemergeasEVofferingsexpandbeyondtheinitialwaveofpredominantlypremium-specproducts.EngineersnotethatbenchmarkingactivityandtheintroductionofnewanalysisandtestingtoolsrelatedtoNVHmitigationareat“crazy”levels.
“OurinterestinacousticallyimprovedvehiclesalwaysisgoingtoaccelerateandtheNVHtechnologymustalwaysmeetcustomerexpectations,”observedPranabSaha,whosecompanyKolana&SahaEngineersspecializesinacoustics,noiseandvibrationanalysisandtesting.HenotedthatsomeofthelatestEVdesignsshowprogressinattackingbothNVHsourcesandtheirpropagationpaths.Thereislessrelianceon“patch”materials—urethanefoamsdeployedinbodycavitiesandmasticsbakedintounderbodyareasthataddmass,costandcomplexity.ButSahaandotherexpertsdonotbelievethoseso-called“Band-Aid”sounddamperswillbeeliminatedentirely.
“Occupantsshouldnothearanythinggoingonunderneaththeminthebatterypackandelectricdrivesystem,whileoutsidethevehiclenoiseremains,”Sahaasserted.“Atsomepoint,thosenoisesaregoingtobecomeaqualityissue.”
CustomerexpectationsofrefinementinEVsversustheincumbentIC-enginevehiclesarestillevolving.InICEvehicles,about50%ofNVHissuesarerelatedtothepowertrain.Theotherhalfaregeneratedmainlybyroadandwindnoise.InEVs,thenoisesourcesaremorebalanced;theelectricdriveunit(EDU)noiseisimportantbutroadnoiseatlow-tomid-speedsandwindnoiseathighspeeds“tendtodominate,”explainedKiranGovindswamy,seniorVP-Drivetrain,e-MobilityandVehicle,atFEV.
“Onewaytolookatthisis,noisecomingfromthetractionmotororgeartrainisonlyimportantifthecustomerhearsitinthevehicle,”hesaid.“Sufficientroadandwindnoisecan,toanextent,maskthenoisecomingfromtheEDU.Thismightbebeneficial,butyoudon’twantit[roadandwindnoise]tobesobadthatthecustomerfeelsit’snotarefinedvehicleatall.”
Evolvingsimulation
Govindswamynotedthathigher-endEVsthataremorerefinedtypically“doaverygoodjob”atreducingtheroadandwindnoiseenteringthecabin—butsometimesattheexpenseofexposingthehigher-frequencywhineofthehigh-rpmelectricmachineandgeartrain.Powerinvertersalsoexhibithigh-frequencynoiseintherangeof10,000Hz.
ThreemainsourcesofEDUnoiseincludeelectromagneticnoisefromthemotoritselfthatradiatesofftheunit’shousing;geartrainnoise,andoverallmechanicalnoisefrombearings,fluidsandrotatingsystems.Definingthenoisesources,theirtransmissionpaths,andestablishingacceptablelevels,isalmostaclinicalprocessforNVHengineers.FEV,forexample,employssimulation-basedprocessesthatdevelopEDUstomeetcustomeracoustictargets.
Simulationisevolvingandcontinuestoimprove,butit’sstillaworkinprogressintermsofcorrelation,expertsassert.“Werelyalotonsimulation,butIthinkmanynewcompanies[automotivestart-ups]relyonittoomuch,”Sahaopined.“They’renotverifyingthesimulatedresultsuntilverylateindevelopment,ortheirsimulationpredictionsmaynotbetotallycorrect.We’veseenexamplesofpredictionsbeingadjustedbasedonwhatthemeasurementsweretelling.Ican’tunderstandhowtheygettotheirtarget.”
HenotedthatwhiletheestablishedOEMswhoaremovingintoEVsalsoareusingpredictivesim,“theyhaveamuchstrongermeasurementbackground”andverifytheirpredictionsmuchsoonerinthedevelopmentprocess.
LightweightingandSimulation
Thealarmingmassoflithium-ionbatterypacksinelectrictrucks,largeutilitiesandhigh-performanceEVshasledbodyengineerstooffsetthatweightwithlightweightingmaterialsolutionsthat,insomecases,havecausedNVHissuesatthecabinlevel.
“Intheinterestoflightweightingwe’reseeingsteelandothermetalsbeingreplacedbypolymericmaterials,andbarrierdecouplersbeingreplacedbydissipativesystems,”notedSaha.“Therearevibracousticissuesassociatedwithlighterweightbodypanels.Passengerswantaquietercabin,whiletheengineeringteamisfocusedonmassefficiency.Thisisbringingnewanddifferenttypesoflightweightdampingmaterialsandothertechnologiesintothepicture.”
ReducingthemassofalltheadditionalNVHtreatmentsandacousticpackagesisarelatedfocus.“Thiscomesbacktotheimportanceofreducingnoiseatthesource,”saidGovindswamy.“Alotofsimulationworkisgoingintothat,andit’sachallenge.Butit’salsoteachingengineerstouselighterweightacousticalmaterialsmoreefficiently.”
Aswithallareasofvehicledevelopment,simulationisincreasinglyintegraltoNVHmitigation.“Iseeitasapyramidwiththesign-offatthetoptipandanimmenseamountofworkthatgoesonunderneathittogettothesign-offpoint,”observedDaveBogema,seniordirectorofproductmanagementatVI-grade,makerofsimulationtoolsforNVHandvehicledynamicswork.NVHanalysisbeginsatthedesktopwhereengineersusingthelatest,increasinglycapableanalysissoftwarerapidlyworkthroughvariousideasandweedoutthosethatareunfeasible(seesidebar).Thenextstepissubjectiveevaluation,whereNVHreallymustbeexperiencedifdecisionsaretobemadewithconfidence.
“Youcangetacertainlevelofanswersfromthedesktop,”Bogemasaid.“Butdesktopsimulationdoesn’thavethefullbenefitofimmersionandrealitythatexperiencingvirtualprototypesonphysicalsimulatorsdelivers.”
Predictingacousticnoiseandvibrationgeneratedbyelectricmachinesischallengingduetothevarietyofphysicaldomainsandcomplexinteractionsamongthesedomains.Electromagnetics,thermodynamics,andvibro-acousticanalysesarerequiredinacoupledfashionforaprecisepredictionofacousticnoisegeneratedbyelectricmachines.AccordingtoAnsysSolutions,therearefouressentialelementsforaccuratelypredictingacousticnoise:needforahigh-fidelitysimulationsolutiontoaccountforallthephysicsinvolved;aplatformtocoupleallthedifferentphysicselements;abilitytoparameterizeandoptimizemachinedesignparametersforeachofthephysicsinvolved,andhigh-performancecomputingcapabilitytoacceleratethesimulation.
There’salsovehicledynamics,inmanywaysinseparablefromNVHincludinghowtheyinfluencethevirtual-prototypeevaluationprocessandtheoccupant’sperceptionofvehiclerefinement.PhysicalsimulationtoolsareexpandingtomeetthemanyfacetsofEVrefinement.
“Whenyoudriveavehicle,youfeeleverythingatthesametime,”VI-grade’sBogemasaid.“Ifyou’redoingridecomfort,whichisamulti-sensorymotion,vibration,andsoundexperience,puttingNVHandvehicledynamicstogetherdeliverstherepeatabilityandcontrolthatarevitaltooverallfidelity.”HiscompanyrecentlylauncheditsnewCompactFull-SpectrumSimulator(FSS)atthe2023SAENoiseandVibrationConference.Capableofsimulationsfrom0.5Hzto20kHz,theCompactFSSdeliversbothprimaryandsecondarydrivingmotion,vibration,andsound,simultaneously.Whilenotatraditionalhexapod-typesimulatordesign,theFSS’sfourlegsenableittoaccuratelyreplicatethemotionoftheroadasgeneratedwhendrivingoverpotholes,cobblestones,oranyothersurface.Itsvibrationshakersproducehigh-frequencyvibrationthroughthesteeringwheelandtheseat,inadditiontothemotionfromtheroad.
VI-gradealsooffersadedicatedCompactNVHdrivingsimulatorthatallowsengineerstodialinexactlywhatthecarisgoingtofeellikeforNVH.Itsseatstructureallowsanarrayofvirtualseatdesignstobetried,wheretheFSSrequiresaphysicalseatchange.ThededicatedNVHsimulator“caninstantlychangetheseatparametersandfeelthedifferencebetweenseats,”Bogemanoted.“They’redesignedfordifferentusecases,”hesaid—theFSSisverymuchaimedatridecomfort;theNVHversionisfordialinginrefinement.”
Engineersalsoarerealizingtheycandosounddesignatthedesktop,interactively,andcomeupwithdifferentsoundscapesforthecar.Vibrationplaysintothat.“DoyoureallyneedthewholemotionofthecarinthesounddesignMaybenotallthetime,”Bogemasaid.
BespokeNVHComponents
RaisingthethresholdsofvehiclerefinementisnotexclusivetoEVs.ExpertssayEVsandhybridsaredrivingnewdesignsandNVH-reductionapproachesacrossproductsegmentsincludingthosestilldominatedbyIC-enginevehicles.Theynote,however,thatcostpressurescanmakesophisticateddesignsatoughsellunlesstheirNVHperformanceisexceptional.
AnexampleofanewNVH-focusedcomponentisanewtunablebracketforairsuspensionair-supplyunits(ASU)recentlylaunchedbyVibracoustic,aleadingglobalautomotiveNVHsolutionssupplier.ThesimpleyetsophisticatednewASU,shownintheaccompanyingimage,featuresaplasticbase(previouslysteel)forimproveddamping,andbellow-stylerubberbushingsandbumpstops.Thebushings’specialmaterialpropertiesgivetherequiredstiffnesslevelswhilealsodampingbothradialandaxialexcitationsgeneratedbythecompressor.
Thenewmountingbracketislighterandmorerobustthantraditionalbrackets,accordingtoVibracoustic,andenablesNVHtuninginalldirections—somethingnotpossiblewithcoilspringstypicallyusedinsuchapplications,thecompanyclaims.Additionally,thebellow-typebushingdesignallowsforhighdisplacementatlowstrainlevels,replicatingtheperformanceofsprings.Therubbermaterialalsohelpsmaintainresonancepeakswithinareasonablerange,becausetherubbercompounddemonstratesadynamicstiffnesspeakthatisupto60%lowerthanofacoilspring,companyengineersclaim.
ThekeytoNVHscienceandengineeringinEVsgoingforward,accordingtoGovindswamyatFEV,isstrikingabalance:meetingcustomerrefinementexpectationswithoutdegradingvehiclerange.“Ifyoucansecuretheelectricmotor’sefficiencyandacceptaslightlyhighernoisebutimprovethetraditionalvehicletominimizetheeffecttothecustomer—that’sthechallengewe’reworkingon.Anditcomesdowntosystemsoptimization.”
NVHsoftwaresimulationsolutions
AmongdozensofsuppliersofferingNVHsimulationsoftwaretoolsarethesepopularproductsusedbySAEreaders:
PartofHexagonAB(seebelow),ActronisanFE-basedtoolformodelingacousticbehaviorofmechanicalsystemsandcomponents.ItiswidelyusedtosolveNVHproblemsinthemid-frequency(400-1500Hz)rangethatarecriticalforEVdesign.An‘open’tool,itleveragesexistingFEandCFDsimmodelsandisusedtostudyEVtransmissionandancillary(pumps,compressors)noisesources.GMengineersusedActrantooptimizenoise-dampingtreatmentsintheCadillacLyricEV.
AltairTheHyperWorkssimulationsuitecontainsabroadrangeofsolutionsforNVHmodelbuild,assembly,diagnostics,analysisandoptimization.Thesuite’scustomizableNVHDirectorautomatesthetasksinvolvedinNVHanalysisbyintegratingtheentireprocessofmeshing,assembly,loadcasesetup,andpost-processing,toreducefull-vehicleNVHsimulationtime.
AnsysRapidNVHworkflowfortheconceptdesignstagecomparesnoiselevelsfordifferente-motordesigns/topologiestopredictthenoiseoverafullspeedsweep.Itcanidentifythecauseofmotornoiseearlyonandhelpmakerelevantdesignchangesintrade-offwithothermotorperformancetargets,allowingtheNVH,thermal,andelectromagneticbehaviortobeinvestigatedatthesametime.TheNVHworkflowisintegratedintoAnsysMotor-CADtoprovidedesignerswithvariousrepresentationsofforce,displacement,andacousticpower.2Dand3DmodelscanthenbegeneratedinAnsysMaxwellandvibroacousticanalysisperformedinAnsysMechanical.
AVLTheX-FEMNVHisa4-channelacquisitionmodulesuitableforusewithallcommonacousticsensoroutputtypessuchasvoltage,chargeandICP/IEPE.Eachchannelcanbeindividuallyconfiguredandrawsignalsarestoredinacompressedfileathighresolutionandintime-synchronizedformats.AnoptionalNVHTOOLBOXforAVLIndiComorAVLConcertoincludesthemostcommonNVHanalysistoolsandonlineNVHmacros.
Brüel&KjrDesktopNVH,SimSound,SourcePathContribution,andVSoundallowengineerstodesignandevaluateinteriorandexteriorvehiclesoundsforvehiclesofanyconfiguration.Insight+enablesthetotalexperienceofNVHdata–creatingsoundsdirectlyfromCAEmodelsthatNVHengineerscanlistentoandexperience.TheCAEmodeldatacanbecombinedwithtestdatatocreateanimmersive,realisticenvironment.
DassaultThewidelyused,iconicSIMULIAsuiteoffersacomprehensivesimulationtoolsetforNVHwork.
DewesoftAmongtheNVH-focusedtoolsisSoundQualityMeasurement,whichaddressestheneedtoempiricallyevaluatehowsoundproducedbydifferentkindsofmachinesisperceivedbythehumanear.Thetoolhelpsengineersdeterminehowthesoundisperceived,tunethesound,andmakeitappealingtothecustomer.
HexagonThecompany’sRomaxSpectrumenableselectro-mechanicalpowertrainNVHsimulationandofferscomplete,parametricwhole-systemmodellingofthepowertrainincludinggearandbearingcontactsurfaces.TheRomaxsuiteoffersinterfacestothird-partyCAEtools,includingActranforacoustics:Adamsformultibodysim;JMAGandMaxwellforelectromagneticsimulationNastranforFEmodeling,andVI-gradeforvehicleNVHandsoundquality.
SiemensDigitalIndustriesSiemens’SimcentersuitecontinuestoaddNVHanalysistoolsthatbenefitfromthedigitaltwinapproachtoaccuratelypredictingvehicleinteriorandexteriorNVHperformance.