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.
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