Audio Test for ANC & ENC Function

1.ThedevelopmenthistoryofTWSearphones

TWSearphonesarealsoknownasTrueWirelessStereo(TrueWirelessStereo)truewireless stereoTheyaremainlyconnectedtomobilephonesthroughBluetoothmoduleswithoutwires TheearlyBluetoothtechnologywasimmature,resultinginpoorsoundquality,whichwasonly suitableforbusinesscalls.After2008,theBluetoothA2DPprotocolbeganpopularizing,andthefirst batchofconsumer-gradeBluetoothheadsetswasborn(NotTrueWireless) In2014,thefirst"TrueWireless"BluetoothheadsetwaslaunchedStill,themarketresponsewas notgreat,untilafterthereleaseofApple'sAirpodsin2016,accompaniedbythebirthofBluetooth 50and51technology,theaudiotransmissionlosswascompressedtotheminimum,The"True Wireless"Bluetoothsmartheadsethasusheredintheoutbreak.

2.2IntroductiontotheconceptofENC/ANC

2.1ENCConcept

Activenoisecancellationandenvironmentnoisecancellationaredifferentnoisecancellation technologiesActivenoisecancellationistooffsetambientenvironmentnoisetothegreatestextent, allowingpeopleusingheadphonestoenjoyaquietenvironment,whileenvironmentnoise cancellationisanapplicationintheotherdirection,itallowspeopleusingnoise-canceling headphonestomakeacallonthesideofanoisyroad,onaspeedingmotorcycle,inamovingcar withmusicon,orinacarwithwindowsopen.Thepersonontheothersideofthephonecanhear yourspeechclearly,andthenoisebasicallydoesnotpassSimplyitmeans,activenoise cancellationmeansthatpeoplewhouseheadphonesfeelbetter,andenvironmentnoise cancellationmeansthatpeopleontheotherendofthephonefeelbetter

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2.2ANCconcept

WiththedevelopmentofTWStechnology,anotherequallypopulartechnologyisANC(ActiveNoise Cancellation),whichisactivenoisecancellation,akindofnoisereductiontechnologyappliedinthe headphonesfornoisereduction

TheANCnoisereductiontechnologyanalyzesthesoundwavesofthenoise,andthen superimposesandneutralizesthembysendingreversesoundwaves,soastoachievetheeffectof eliminatingnoiseTheadvantageisthatthecontroleffectoflow-frequencynoiseisremarkable,and itcaneffectivelyisolatelow-frequencynoiseandreducetheimpactofnoiseonpeople'shealthIn general,theeffectivefrequencyofANCactivenoisecancellationisbetween50Hzand2kHzFor noiseexceeding2KHz,noise-cancellationheadphonescanreduceitbyusingpassivemethods throughthestructuraldesignandmaterialselectionoftheheadphones

3ENCandANCtestsolutions

Differentnoisecancellationsolutionsbringusersadifferentnoisecancellationexperience,MegaSig canprovidecustomersandpartnerswithacompletetestinstrumentandsystemsolutionsfrom researchanddevelopmenttomassproduction.

3.1ENCtestsolution

Firstlet'stakealookatENC'stestsolutions

Thereare3maintechnologiesfornoisereductionincalls: 1

Uplinkboneconductiontechnology

ThesethreetechnologiesarenotnewOurmobilephoneshavetwomicrophones(oneisnexttothe chargingportandtheotherisnexttothecamera),whichhavebeensilentlyhelpingusmakecalls andnoisereductionformanyyears(so,sometimesweareaccustomedtoturningofftheearphones andusingthemobilephonedirectlywhenmakingaphonecallwithearphonesforfearofbeing unclear.Thisisthemainreason).

Theessenceofuplinkboneconductiontechnologyistotransmitthecallcontentbycollectingthe vibrationsignaloffaceorvocalcordThenoiseconductionmediumisair,andthevibrationofyour faceorvocalcordsaredirectlycollectedbytheaccelerationsensor,whichcanisolatethe environmentalnoise.Thistechnologyiswidelyusedinthemilitary,makingaphonecallinatankor inahelicopter. 3.1.1EnvironmentalNoiseCancellationeffecttestintheResearchand Developmentstage

ThesystemarchitectureisinthefigurebelowWeusetheturntableTT625tomeasuretheHFP transmissionenergyofeachangleoftheearphoneIfweusethefrequencysweepsignal,itcanbe consideredthattheadaptivefilterhasnotconvergedyet,ie,thereceivedsignalcanbeconsidered tobeenhancedbybeam-formingonly

b)AdaptivefilteringalgorithminR&Dstage

DuringR&Dtestingnotonlyneedstoquantifythebeam-formingeffect,butalsoneedstocarryout theconvergenceeffectoftheadaptivefilter,andeventesttheconvergencetime.Bothofthemare supportedbyAudioExpertplatform

c)BoneconductiontechnologyintheR&Dstage

Boneconductioncanbedividedintouplink/downlinkboneconductioncalltechnology,the formeristoallowtheotherpartytohearclearly,andthelatteristoallowyourselftohearclearly.We willfocusontheuplinkboneconductiontechnology

Intheprocessoftalking,thesoundofourownspeechistheusefulsignalwereallywantto transmit,butinaddition,therearevariousnoisesgeneratedbymachineryandequipment,wind noise,surroundingpeople,etc,whichcanbecalledNoisesignals

Theessenceoftheuplinkboneconductiontechnologyistocollectthevibrationsignalofthecheek byinsertinganaccelerationsensorchipintotheearphoneandtransmittheeffectivesignalasthe contentofthecallTheconduction(airconduction)oftheambientnoisedependsonthemicrophone, soitwillnotbecollectedbytheaccelerationsensor,whichcanachievetheeffectofairconduction noisefiltering

Whenwespeak,inadditiontothevibrationoftheface,thevibrationofthebridgeofthenoseisalso relativelystrong,sothistechnologyisnotonlyusedinthefieldofheadsets,butalsoinVRorAR smartwearabledevicestoimprovetheeffectofcalls

Fromthetestoftheuplinkboneconductioncalltechnology,itcanbedividedintothreeparts:the incomingIQCchiptest,thesemi-finishedbonevoiceprinttestandthefinishedbonevoiceprinttest ThefollowingthreetestsaresupportedandcompatiblewithourMegaSigsystem

3.1.2Testofcallnoisereductioneffectinmassproduction

Overthepasttwoyears,MegaSighassupportedbatchesofheadsetswithENCfunctionandmass productiontestingofTWSearphoneswithENCfunctionNowwewillintroducetheaccumulated experiencetoyou

Thereare3maintestingmethodsformassproduction: 1,Signal-to-noiseratiotest 2,Looptest 3,Switchtest

Thereareadvantagesanddisadvantagestothesethreemethods,andthesystemofMegaSig supportsthemseamlessly.Theanalysisandintroductionarebelow.

1)Signal-to-NoiseRatiotest

Thismethoddoesnotrequirethesupportofthechipmanufacturer'sinstructions,andbasically,any instrumentcansupportit,andthemeasurementenvironmentissimilartothereal-timeenvironment, andthenoisereductiondatatestedisclosetotherealeffectHowever,becausethealgorithmis alwayson,itiseasytobedisturbedbytheenvironment,andthetestdataisnotverystable. Sometimesitneedstoberetestedtopass,andittakessometimetowaitforconvergence,sothe testefficiencyandyieldarerelativelylow

2)Looptest

Thismethodrequiresthesupportofchipmanufacturersorsolutionprovidersandhavetocontrolthe DUT.Moreover,intheformofTWS,itdoesnotsupporttoomanythimblepoints,soSPPorBLE

protocolisgenerallyused.However,sincethistestmethodstripstheinfluenceofthealgorithm,itis possibletomeasurethequalityandassemblyerrorsofthedualmicrophones.Theconsistencyis veryhigh,thereisnoconvergencetime,andthetestefficiencyisalsohighHigh-endbrandsalso payattentiontoENCquality,basicallywilltendtousethismethodAtpresent,MegaSig’ssystem cansupporttheDUTcontrolofthegeneralBluetoothchipsonthemarket

3)Switchtest

Inthismethod,thepenetrationeffectofnoiseenergyistestedthroughtheswitchoftheDUT. Sincethistesthasonlyoneangle,thenoisesuppressioncapabilityofbeam-formingisbasically ignored,theDUTcommandisalsorequired,andtheconvergencetimeisrequired,sothis methodisleastrecommendedformassproductionHowever,itisrecommendedtouseitinthe researchanddevelopmentstagetotesttheeffectoftheadaptivefilter,andsomemanufacturers choosethismethodintheearlymassproductiontestofsingle-micnoisereduction.

3.2ANCtestsolution

ThenoisereductioneffectofANCnoise-cancelingheadphonesisdeterminedbytwoaspects,oneis thedesignofthefilterchainoftheproduct,andtheotherisaseriesofnoisereductiongainvaluesof theproduct.IntheR&Dstage,thefilterchaindesignhasbeenfinalizedandwillnotbechangedin themassproductionstageHowever,duetothedifferenceinthequalityofincomingmaterialsfor themicrophoneunitandthespeakerunit,aswellasthecavitydifferencegeneratedduringthe assemblyprocess,tomakeupforthesetoleranceandachievethetargetnoisereductioneffectand balancethenoisereductioneffect,duringmassproduction,thenoisereductiongainvalueneedsto befine-tunedandmodified,andthenoisereductioneffectcanbetestedonlineThetraditional methodistomanuallyadjustthegain,manuallyverifyituntilitmeetsthenoisereductioneffect,and thenmanuallyburnit.

AudioExpert'sANCoptionsupportsallmainstreamnoisereductionsolutionsonthemarket,aswell asautomatedtestingandburningsystemsMegaSigcooperateswithfirst-classODM manufacturersandsolutionprovidersandhassuccessfullypushedthissystemtoR&DandMass production,creatingvalueforcustomersstablyandefficiently

Thesystemalsosupportsthemeasurementofkeyelectro-acousticparametersthatareconcerned intheproductionprocessofheadphones,microphones,andothercomponentswhentheANC functionisturnedoffItisaone-stoptestsystem

Thesoftwareparameterconfigurationofthesystemissimpleandfast,thetestingprocessisfast andaccurate,theproductionefficiencyismaximized,theproductqualityisguaranteed,andthe companywinsthetimeandthetrustofthecustomers,andfinallyobtainsalargerorderand achievesawin-winsituation