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简介：Inthispaper,anovelmethodforThreedimensionalactivesoundfieldcancellationisproposed.Theoptimumsoundcancellationsindifferentsituationsmaybeobtained.Anarraywhoseelementslieonasetofringsplacedonthesurfaceofascatteringobjectisconsideredasthedevice.Itisquitepossibletocancelthescatteredsoundfieldtoanyarbitrarylevelovereitherthewholespaceorapartialareaofinterest,aslongasthenumberofthearrayelementsissufficient.

简介：Thisreportdescribesanewmethod,theself-searchingmethod,tofindeigenraysinanoceanwherethereisathree-dimensionalsoundspeedperturbationblobonauniformsoundspeedbackground.Comparedwiththetraditionalshootingmethod,thismethodcanreducethenumberofraycalcula-tionsbyabouttwoordersofmagnitude,andaneigenraycanbefoundbycom-puterprogramwithoutmanualintervention.

简介：Ultrasoundsimulationforcarotidarteriesishelpfultotheperformanceassessmentsofvesselwalldetectionandsignalprocessingmethodsbyusingultrasoundtechniques.Anultrasoundsimulationmethodofcarotidarterywallwithathree-membranestructureisproposedinpresentstudy.Accordingtotheultrasoundspeckledistributionsvaryingwiththeshapesanddensitiesofscattererdistributions,aswellasthestatisticresultsoftheclinicalimages,theparametersofdistributions,densitiesandintensitiesofscatterersfordifferentkindsoftissuesinthecarotidarteryphantomsaredetermined.EachregionisacousticallycharacterizedusingFIELDIIsoftwaretoproducetheradiofrequencyechosignals,fromwhichultrasoundimagesarederived.Theresultsbasedon30simulationsshowthattheechodistributionsoftheintimae,mediae,adventitiasandbloodareconsistentwiththeclinicalones.Moreover,comparedwiththeresultsfromthecentralfrequencyof8MHz,themeanmeasurementsforthicknessesoftheintima,mediaandadventitiamembranes,aswellasthelumendiameterfromthesimulationimagesbasedon12MHzarethesameasthepresetones,andthemaximumrelativeerrorsarethe4.01%,1.25%,0.04%and0.15%,respectively.Thesimulationunderthisconditionismorerealistic.

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简介：Toimprovetheperformanceofsoundsourcelocalizationbasedondistributedmicrophonearraysinnoisyandreverberantenvironments,asoundsourcelocalizationmethodwasproposed.Thismethodexploitedtheinherentspatialsparsitytoconvertthelocalizationproblemintoasparserecoveryproblembasedonthecompressivesensing(CS)theory.Inthismethodtwo-stepdiscretecosinetransform(DCT)-basedfeatureextractionwasutilizedtocoverbothshort-timeandlong-timepropertiesofthesignalandreducethedimensionsofthesparsemodel.Moreover,anonlinedictionarylearning(DL)methodwasusedtodynamicallyadjustthedictionaryformatchingthechangesofaudiosignals,andthenthesparsesolutioncouldbetterrepresentlocationestimations.Inaddition,weproposedanimprovedapproximatel_0normminimizationalgorithmtoenhancereconstructionperformanceforsparsesignalsinlowsignal-noiseratio(SNR).Theeffectivenessoftheproposedschemeisdemonstratedbysimulationresultswherethelocationsofmultiplesourcescanbeobtainedinthenoisyandreverberantconditions.

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简介：双交换边界元素方法(DRBEM)被使用与三维的潜在的流动预言管和silencers的声学的特征，并且基本原则和建议方法的数字过程是到常规边界元素方法(CBEM)的introduced.Compared，DRBEM在声学的管理方程考虑流动马赫数字的第二个顺序术语，它对有更高的马赫数字的状况合适亚声的flow.The四杆的parame