简介：Timereversalisappliedtotheunderwaterspreadingspectrumcodingcommunication.Onthebaseofanalyzingthefocusingcharacteristicsofthetimereversalinunderwaterwaveguide,thetimereversalisstudiedtoovercomethewavedistortionoftheencodedsignalcausedbythemulti-patheffect.TheexperimentresearchforunderwatercodingcommunicationiscarriedoutinalabwatertankandthecorrespondingtheoreticalanalysisisalsoconductedbyBinaryPhaseShiftKeying(BPSK)encodingandBarkercodewith7chipsforthespreadingspectrumsignal.Theresultsshowthatthetimereversalcanimprovethefocusinggainandincreasetheratiooftheprincipaltothesecondlobeofthecodingsignal,andcandecreasethebiterrorrateandincreasethecommunicationdistance.

简介：Auditorymodelhasbeenappliedtoseveralaspectsofspeechsignalprocessingfield,andappearstobeeffectiveinperformance.Thispaperpresentstheinversetransformofeachstageofonewidelyusedauditorymodel.Firstofallitisnecessarytoinvertcorrelogramandreconstructphaseinformationbyrepetitiousiterationsinordertogetauditory-nervefiringrate.ThenextstepistoobtainthenegativepartsofthesignalviathereverseprocessoftheHWR(HalfWaveRectification).Finallythefunctionsofinnerhaircell/synapsemodelandGammatonefiltershavetobeinverted.Thusthewholeauditorymodelinversionhasbeenachieved.Anapplicationofnoisyspeechenhancementbasedonauditorymodelinversionalgorithmisproposed.Manyexperimentsshowthatthismethodiseffectiveinreducingnoise.EspeciallywhenSNRofnoisyspeechislowitismoreeffectivethanothermethods.Thusthisauditorymodelinversionmethodgiveninthispaperisapplicabletospeechenhancementfield.

简介：Anumericalmethodofsolvingacousticwavescatteringpnbleminfluidsisdescribed.Radiationboundarycondition(RBC)obtainedbyfactorizationmethodofHelmholtzequationisappliedtotransformingtheexteriorboundaryvalueprobleminunboundedregionintooneinafiniteregion.CombinedwithRBCandscatterersurfaceboundarycondition,Helmholtzequationissolvednumericallybythefinitedifferencemethod.ComputationalresultsforsphereandprolatespheroidalscatterersareinexcellentagreementwitheigenfunctionsolutionsandmuchbetterthantheresultsofOSRCmethod.

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简介：Thereciprocitymeasurementtheoryinanomalousreverberantsoundfieldswasinvestigated.AnimprovedmethodWasproposedduetotheinterrelatederrors.ThesourcevolumevelocityWascorrectedbyspatialaverageofmeasurementresultsandevaluationofthereverberantsoundfieldinfluenceonacousticenergydensity.Theresultwasvalidatedinunderwaterexperiment,correctedreciprocitymeasurementresultswerealmostthesameasdirectmeasurementresults.Itindicatesthatreverberantsoundfielddoesnotaffectthevaliditvoftheprinciple,butinfluencestheobtainmentofsourcevolumevelocity,theninfluencesthemeasurementoftransferfunctionswiththeprinciple.Theproposedmethodissimpleandeffectiveinanomalousreverberantsoundfields.Thestudymavbevaluablefortheapplicationswhicharebasedontheprinciple.

简介：常规MVDR适应beamformer是用真实的声学的地的narrowbandCSDM估计最佳的beamforming重量的高分辨率的narrowbandbeamformer。在实际应用，MVDR算法需要长观察时间估计协变性矩阵。这个固有的性质使本地化移动迅速的目标困难。为宽带信号，MVDR算法需要转换增加计算要求的每CSDM。为相关来源，因为信号将取消对方，MVDR的性能将戏剧性地降级。一个快会聚的MVDR算法基于subbandsubarray处理被建议。完整的频率乐队被划分成subbands的集合，线数组被划分成subarrays的集合。为每subband，减少的尺寸的STCM是计算的。快会聚的MVDR算法和空间光谱评价的然后适应的beamforming重量被获得。同时，空间光谱评价能用两方面的空间变光滑方法为相关来源被做。模拟和试用数据的结果证明建议方法有高分辨率、在即时附近的集中性质，两方面的空间变光滑有decorrelation的令人满意的有效性。

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简介：Withtheincreasingofdetectionabilityofpassivesonar,theweaksignaldetectionprobleminmultipleinterferencesbecomesmoreandmoreimportant.Inthetime/bearingrecord(TBR)displayofsonardetection,whenthereexisttracesofmultipleinterferences,theidentificationofweaksignalisdifficultorimpossible.Theadaptivenoisecancellationtechniqueprovidesthetheoreticalbasisforsuppressingstronginterferences.Butthesolutionforfindingthesteady-stateoptimumfiltermatrixisquitedifficultduetotherealtimecalculationofinversematrixofinputdatacorrelationmatrix.Theiterativeinversebeamforming(IBF)algorithmforsolvingtheoptimumfiltervector,whichisexpressedbyinversematrixoftheoceanenvironmentdata,isderivedinthispaper,bywhich,theoptimumfiltercanbeeventuallyexpressedasasumofseriessimplematricesofconstructedfromsensordata.Basedonthealgorithmproposedinthispaper,someexamplesofatseaexperimentareprovided.Thestronginterferencesarecancelledandtheweaksignalisemerged,evenitdidn'tappearintheconventionalbeamforming(CBF)processing.

简介：Tosolvebladenumbercharacteristicextractionproblemoflownoiseships,phasecharacteristicsofshipradiated-noisedemodulationspectrumharmoniccomponentsusinghigherorderspectrumanalysiswereconsidered.Throughanalyzingalargenumberofshipradiatednoisedata,itpointsouttheexistingphasecouplingrelationshipbetweentwoorthreeharmoniccomponentsofdemodulationspectrum.Thephasedifferencebetweenlinespectrumofbladefrequencyandthesumoflinespectrumatshaftfrequencyanditssomeharmoniccommonlyiszeroorotherconstant.Higher-ordercumulantisgivenandhigher-orderspectrumissimulatedwhenabovephasedifferenceisanon-zeroconstant.Theapplicationofphasecouplingrelationshipisstudied.Accordingtothehigher-orderspectralanalysisofsomeweakmodulatedshipradiatednoise,itisindicatedthatthephasecouplingrelationshipandhigher-orderspectralanalysiscanimprovetheabilitytoextractpropellerparameters,especiallyfortheweakmodulation.

简介：这份报纸在表面上论述一个最佳的图案声学的波浪用模式COM联合的反射延期线当模特儿。SAW设备的思考系数S11被推出评估设备表演。典型的锯反射延期线由沿着声学的繁殖方向放的压电的底层，interdigital变换器IDT和几个反射镜组成。设备的设计参数的影响反射镜例如IDT的结构，打字，设备性能上的等等被调查，并且最佳的设计参数是坚定的。基于这些参数，434MHz看见了反射延期与单个阶段排队单向性的变换器和三个shorted栅栏反射镜在41上被制作

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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