南郵專業(yè)英語報告-信號處理導論完整版(包含翻譯-原文和單詞)

南京郵電大學專業(yè)英語譯文報告學號學生姓名指導老師指導單位翻譯日期翻譯文獻IntroductiontoSignalProcessing譯文部分S.J.Orfanidis,IntroductiontoSignalProcessing,PrenticeHallInternational,Inc.,2003清華大學出版社有影印版，2003.7，中文書名：《信號處理導論》8.2數(shù)字音效象延時、回聲、回響、梳理濾波、（flanging）凸緣（法蘭）、合唱、pitchshifting(分聲步)、立體聲、變形、壓縮、擴張、噪聲消除、均衡等等這樣一些音響效果在音樂制作和播放時是必不可少的。有些在家庭影院和汽車音響中已經(jīng)使用。大多數(shù)這樣的音響效果是用數(shù)字濾波器來實現(xiàn)的。這種數(shù)字濾波器也許是單獨的一個模塊，也可能是內置在鍵盤或音調生成這樣的器件內部。一般說來數(shù)字音效信號處理器如圖8.2.1所示。圖8.2.1數(shù)字音效信號處理數(shù)字音效處理器的輸入是由鍵盤或紀錄在其他介質上的模擬信號，用一定的抽樣率抽樣。抽樣好的信號用DSP算法處理好以后再模擬重建輸出到下一級音頻通道中，如喇叭、混響器等等。全數(shù)字式系統(tǒng)可以不需要抽樣、重建部分，數(shù)字式輸入音頻信號可以一直在后續(xù)的DSP處理中保持數(shù)字化。本屆中我們將討論一些基本音響效果，如延時、回聲、潤色、合唱、回響、動態(tài)處理。具體的濾波器設計將在第十章和第十一章討論。8.2.1延時、回聲、梳理濾波程序chorus.m演示的是正弦信號經(jīng)合唱處理后的情形。調相(PhaseShifting)對吉他手、鍵盤演奏人員、歌唱家來說是經(jīng)常采用的一種效果。調相是把聲音信號用一個窄帶陷狀濾波器過濾，再把過濾信號的一部分與源信號相加而得到的。陷點的頻率以可控的方式調節(jié)，比如說可以用一個低頻振蕩器，也可以用腳踏板控制。陷點附近的頻率有較強的漂移，與原來的直接聲音結合，使得相位在頻率軸上發(fā)生抵消或加強，整個相位在頻率軸上出現(xiàn)波動。一般說來，典型的單零點陷狀濾波器的幅頻響應和相頻響應如圖所示。notch.m。(seepage252forthereviewofnotchfilter)。注意到相頻響應在相點處等于0，而在相點附近變化極快。§6.4.3中，我們討論了一種構造陷狀濾波器的簡單方法，也就是相設計一個notch多項式N(z)，其零點就是我們要設計的陷點。然后再單位圓以內靠外一點的相同頻率上設置濾波器的極點。這樣的濾波器的傳遞函數(shù)具有以下形式：這樣設計的濾波器可以構造多陷點的相位漂移。選擇ρ接近等于1可以實現(xiàn)非常窄，但是這樣的濾波器不能夠對各個頻率陷點的相位單獨控制。用雙線性變換法(第十一章討論)設計的這種濾波器可以對陷點頻率和3-dB寬度進行精確控制。這樣設計的濾波器單陷點濾波器的傳遞函數(shù)具有以下形式：(8.2.22)其中參數(shù)b用3-dB寬度Δω表示為：(8.2.23)衡量陷狀濾波器的另一個參數(shù)為品質因數(shù)Q，用3-dB寬度表示為：(8.2.24)也就是說，品質因數(shù)越高，陷點寬度越窄。因為處了陷點以外幅頻響應基本上不發(fā)生變化(Flat)，所以可以用多個這樣的濾波器級聯(lián)起來形成多陷點濾波器，各濾波器的陷點頻率和相位可以單獨調節(jié)。舉例來說，要設計一個陷點頻率為ω0=0.35π的陷頻濾波器，品質因數(shù)分別為Q=3.5和Q=35兩種情況下，3-dB寬度為：和有(8.2.3)式計算得到濾波器系數(shù)和傳遞函數(shù)為：幅頻響應和相位響應如圖所示頻率漂移演示程序若陷點頻率隨時間變化，則3-dB寬度也會隨時間變化，濾波器的系數(shù)也是時間變化的。這樣的濾波器的時域實現(xiàn)可以采用規(guī)范形式。比方說，如果陷頻是在ω1±ω2之間以ωSWEEP正弦變化，即ω0(n)=ω1+ω2sin(ωSWEEPn)，可以采用下列樣值處理算法來計算飄動的濾波器系數(shù)，再分別計算每次輸入抽樣的濾波。Flanging、合唱、調相三種效果都是把一個簡單濾波器的系數(shù)設計尾隨輸入抽樣變化而使濾波器成為時變?yōu)V波器。自適應信號處理也是隨時間改變?yōu)V波器的系數(shù)。系數(shù)與時間之間的關系是受某些設計條件的限制，即濾波器系數(shù)相對于輸入抽樣調節(jié)并且優(yōu)化。自適應算法的實施也就是要求濾波器的樣值處理算法當中考慮到隨輸入抽樣的不同系數(shù)有不同的權。自適應濾波應用范圍非常廣，象通道均衡、回聲消除、消噪聲、自適應天線系統(tǒng)、自適應喇叭均衡、自適應系統(tǒng)辨識和控制、神經(jīng)網(wǎng)絡等等8.2.3回響回響回響的時間常數(shù)定義為房間的沖激響應衰減到60dB的時間。一般的影院時間常數(shù)為1.8~2秒。電影院的聲音質量取決于回聲沖激響應，而沖激響應主要是由聲源與觀眾的相對位置決定的。因此數(shù)字上模擬任何一個電影院回響特性幾乎是不可能的事。作為一種簡化，數(shù)字回響濾波器試圖模擬放映大廳具有特征性的回響沖激響應，讓用戶有選擇性的調節(jié)某些參數(shù)，如前期反射的延時時間、或者是總體的回響時間。另一種有趣的回響效果是模擬濾波器無法完成的，這就是截斷IIR響應使其成為FIR而得到gatedreverb(選通回響)并且可以讓用戶調節(jié)截斷的時間。snaredrum(小鼓)的聲音就很適用于這樣處理。逆時間截斷的回響響應在模擬領域是無法做到的。圖示的普通回響濾波器太簡單，難以產生實際的回響效果。Schroeder以依此為基礎來構造復雜的回響器，這種濾波器可以由earlyreflection和latediffuse效果。大部分數(shù)字信號處理中，我們感興趣的是穩(wěn)態(tài)響應，而回響是例外，我們感興趣的是濾波器的暫態(tài)響應，因為正是電影院的暫態(tài)響應才形成了回響效果。穩(wěn)態(tài)響應決定了總體聲音質量。普通回響濾波器穩(wěn)態(tài)頻譜的峰值加強了輸入信號峰值頻率附近的那些頻率。為了避免這種輸入聲音的加強程度不一致，Schroeder提出了一種全通濾波器，這種濾波器的幅頻響應特性為一直線。濾波器的傳遞函數(shù)如下：(8.2.25)其I/O方程如下：(8.2.26)用z=ejω代入傳遞函數(shù)得到頻率響應：(8.2.27)因為分子多項式和分母多項式的幅值相同，所以對所有頻率幅頻響應為常數(shù)。盡管穩(wěn)態(tài)響應為常數(shù)，濾波器的暫態(tài)響應像普通的回響濾波器一樣指數(shù)衰減。事實上，將H(z)永部分分式展開得到：(8.2.28)其中，，把后面一項展開乘幾何級數(shù)得到：其沖激響應為：(8.2.29)圖8.2.17是其框圖實現(xiàn)方法：普通回響器與全通回響器結合就可以形成實際的回響器。Schroeder的回響器就是用幾個普通回響單元并聯(lián)，后面在接上幾個級聯(lián)的全通濾波器組成的。(見本書封面上圖形和page372所示圖)。六個單元中不同的延時是回聲的強度增加，形成的沖激響應具有典型的前期回聲和后期回聲效果。圖示為下列參數(shù)是回響器的沖激響應。英文原文8.2DigitalAudioEffectsAudioeffects,suchasdelay,echo,reverberation,combfiltering,flanging,chorusing,pitchshifting,stereoimaging,distortion,compression,expansion,noisegating,andequalization,areindispensableinmusicproductionandperformance[115–151].Somearealsoavailableforhomeandcaraudiosystems.Mostoftheseeffectsareimplementedusingdigitalsignalprocessors,whichmayresideinseparatemodulesormaybebuiltintokeyboardworkstationsandtonegenerators.AtypicalaudioeffectssignalprocessorisshowninFig.8.2.1.Theprocessortakesinthe“dry”analoginput,producedbyaninstrumentsuchasakeyboardorpreviouslyrecordedonsomemedium,andsamplesitatanappropriateFig.8.2.1Audioeffectssignalprocessor.audiorate,suchas44.1kHz(orless,dependingontheeffect).ThesampledaudiosignalisthensubjectedtoaDSPeffectsalgorithmandtheresultingprocessedsignalisreconstructedintoanalogformandsentontothenextunitintheaudiochain,suchasaspeakersystem,arecordingchannel,amixer,oranothereffectsprocessor.Inall-digitalrecordingsystems,thesampling/reconstructionpartscanbeeliminatedandtheoriginalaudioinputcanremainindigitizedformthroughoutthesuccessiveprocessingstagesthatsubjectittovariousDSPeffectsormixitwithsimilarlyprocessedinputsfromotherrecordingtracks.Inthissection,wediscusssomebasiceffects,suchasdelays,echoes,flanging,chorusing,reverberation,anddynamicsprocessors.ThedesignofequalizationfilterswillbediscussedinChapters10and11.8.2.1Delays,Echoes,andCombFiltersPerhapsthemostbasicofalleffectsisthatoftimedelaybecauseitisusedasthebuildingblockofmorecomplicatedeffectssuchasreverb.Inalisteningspacesuchasaroomorconcerthall,thesoundwavesarrivingatourearsconsistofthedirectsoundfromthesoundsourceaswellasthewavesreflectedoffthewallsandobjectsintheroom,arrivingwithvariousamountsoftimedelayandattenuation.Repeatedmultiplereflectionsresultinthereverberationcharacteristicsofthelisteningspacethatweusuallyassociatewitharoom,hall,cathedral,andsoon.Asinglereflectionorechoofasignalcanbeimplementedbythefollowingfilter,whichaddstothedirectsignalanattenuatedanddelayedcopyofitself:y(n)=x(n)+ax(n?D)(echofilter)(8.2.1)ThedelayDrepresentstheround-triptraveltimefromthesourcetoareflectingwallandthecoefficientaisameasureofthereflectionandpropagationlosses,sothat|a|≤1.Thetransferfunctionandimpulseresponseofthisfilterare:H(z)=1+az?D,h(n)=δ(n)+aδ(n?D)(8.2.2)ItsblockdiagramrealizationisshowninFig.8.2.2.ThefrequencyresponseisobtainedfromEq.(8.2.2)bysettingz=ejω:（8.2.3）8.2.2Flanging,Chorusing,andPhasingThevalueofthedelayDinsamples,orinsecondsTD=DT,canhaveadrasticeffectontheperceivedsound[119,120,128].Forexample,ifthedelayisgreaterthanabout100millisecondsintheechoprocessor(8.2.1),thedelayedsignalcanbeheardasaquickrepetition,a“slap”.Ifthedelayislessthanabout10msec,theechoblendswiththedirectsoundandbecauseonlycertainfrequenciesareemphasizedbythecombfilter,theresultingsoundmayhaveahollowqualityinit.Delayscanalsobeusedtoalterthestereoimageofthesoundsourceandareindispensabletoolsinstereomixing.Forexample,adelayofafewmillisecondsappliedtooneofthespeakerscancauseshiftingandspreadingofthestereoimage.Similarly,amonosignalappliedtotwospeakerswithsuchasmalltimedelaywillbeperceivedinstereo.Moreinterestingaudioeffects,suchasflangingandchorusing,canbecreatedbyallowingthedelayDtovaryintime[119,120,128].Forexample,Eq.(8.2.1)maybereplacedby:(flangingprocessor)(8.2.17)Aflangingeffectcanbecreatedbyperiodicallyvaryingthedelayd(n)between0and10msecwithalowfrequencysuchas1Hz.Forexample,adelayvaryingsinusoidallybetweenthelimits0≤d(n)≤Dwillbe:(8.2.18)whereFdisalowfrequency,inunitsof[cycles/sample].ItsrealizationisshowninFig.8.2.8.Thepeaksofthefrequencyresponseoftheresultingtime-varyingcombfilter,occurringatmultiplesoffs/d,anditsnotchesatoddmultiplesoffs/2d,willsweepupanddownthefrequencyaxisresultinginthecharacteristicwhooshingtypesoundcalledflanging.Theparameteracontrolsthedepthofthenotches.Inunitsof[radians/sample],thenotchesoccuratoddmultiplesofπ/d.Intheearlydays,theflangingeffectwascreatedbyplayingthemusicpiecesimultaneouslythroughtwotapeplayersandalternatelyslowingdowneachtapebymanuallypressingtheflangeofthetapereel.Becausethevariabledelaydcantakenon-integervalueswithinitsrange0≤d≤D,theimplementationofEq.(8.2.17)requiresthecalculationoftheoutputx(n?d)ofadelaylineatsuchnon-integervalues.AswediscussedinSection8.1.3,thiscanbeaccomplishedeasilybytruncation,roundingorlinearinterpolation.Linearinterpolationisthemoreaccuratemethod,andcanbeimplementedwiththehelpofthefollowingroutinetapi.c,whichisageneralizationoftheroutinetaptonon-integervaluesofd.Theinputdmustalwaysberestrictedtotherange0≤d≤D.Notethatifdisoneoftheintegersd=0,1,...,D,theroutine’soutputisthesameastheoutputoftap.Themod-(D+1)operationinthedefinitionofjisrequiredtokeepjwithinthearraybounds0≤j≤D,andiseffectiveonlywhend=D,inwhichcasetheoutputisthecontentofthelastregisterofthetappeddelayline.Thefollowingroutinetapi2.cisageneralizationoftheroutinetap2,whichisimplementedintermsoftheoffsetindexqinsteadofthecircularpointerp,suchthatp=w+q./*tapi2.c-interpolatedtapoutputofadelayline*/Linearinterpolationshouldbeadequateforlow-frequencyinputs,havingmaximumfrequencymuchlessthantheNyquistfrequency.Forfastervaryinginputs,moreaccurateinterpolationmethodscanbeused,designedbythemethodsofChapter12.Asanexampleillustratingtheusageoftapi,considertheflangingofaplainsinusoidalsignaloffrequencyF=0.05cycles/samplewithlengthNtot=200samples,sothatthereareFNtot=10cyclesinthe200samples.Theflangedsignaliscomputedbywithd(n)givenbyEq.(8.2.18),D=20,andFd=0.01cycles/sample,sothatthereareFdNtot=2cyclesinthe200samples.Thefollowingprogramsegmentimplementsthecalculationoftheterms(n)=xandy(n).Adelay-linebufferofmaximaldimensionD+1=21wasused:double*w,*p;w=(double*)calloc(D+1,sizeof(double));p=w;for(n=0;n<Ntot;n++){d=0.5*D*(1-cos(2*pi*Fd*n));time-varyingdelayx=cos(2*pi*F*n);inputx(n)s=tapi(D,w,p,d);delay-lineoutputx(n?d)y=0.5*(x+s);filteroutput*p=x;delay-lineinputcdelay(D,w,&p);updatedelayline}Figure8.2.9showsthesignalsx(n),s(n)=xn?d(n),y(n),aswellasthetime-varyingdelayd(n)normalizedbyD.Recursiveversionsofflangerscanalsobeusedthatarebasedontheall-polecombfilter(8.2.13).ThefeedbackdelayDinFig.8.2.6isreplacednowbyavariabledelayd.TheresultingflangingeffecttendstobesomewhatmorepronouncedthanintheFIRcase,becausethesweepingcombpeaksaresharper,asseeninFig.8.2.7.Chorusingimitatestheeffectofagroupofmusiciansplayingthesamepiecesimultaneously.Themusiciansaremoreorlesssynchronizedwitheachother,exceptforsmallvariationsintheirstrengthandtiming.Thesevariationsproducethechoruseffect.AdigitalimplementationofchorusingisshowninFig.8.2.10,whichimitatesachorusofthreemusicians.Thesmallvariationsinthetimedelaysandamplitudescanbesimulatedbyvaryingthemslowlyandrandomly[119,120].Alow-frequencyrandomtimedelayd(n)intheinterval0≤d(n)≤Dmaybegeneratedby3588.SIGNALPROCESSINGAPPLICATIONSFig.8.2.10Choruseffect,withrandomlyvaryingdelaysandamplitudes.d(n)=D0.5+v(n)(8.2.20)or,ifthedelayistoberestrictedintheintervalD1≤d(n)<D2d(n)=D1+(D2?D1)0.5+v(n)(8.2.21)Thesignalv(n)isazero-meanlow-frequencyrandomsignalvaryingbetween[?0.5,0.5).ItcanbegeneratedbythelinearlyinterpolatedgeneratorroutineranlofAppendixB.2.GivenadesiredrateofvariationFrancycles/sampleforv(n),weobtaintheperiodDran=1/Franofthegeneratorranl.Asanexample,consideragainthesignaly(n)definedbyEq.(8.2.19),butwithd(n)varyingaccordingtoEq.(8.2.20).TheinputisthesamesinusoidoffrequencyF=0.05andlengthNtot=200.Thefrequencyoftherandomsignalv(n)wastakentobeFran=0.025cycles/sample,correspondingtoNtotFran=5randomvariationsinthe200samples.TheperiodoftheperiodicgeneratorranlwasDran=1/Fran=40samples.Thesameprogramsegmentapplieshere,butwiththechange:d=D*(0.5+ranl(Dran,u,&q,&iseed));wheretheroutineparametersu,q,iseedaredescribedinAppendixB.2.Figure8.2.11showsthesignalsx(n),s(n)=xn?d(n),y(n),aswellasthequantityd(n)/D.Phasingorphaseshiftingisapopulareffectamongguitarists,keyboardists,andvocalists.Itisproducedbypassingthesoundsignalthroughanarrownotchfilterandcombiningaproportionofthefilter’soutputwiththedirectsound.Thefrequencyofthenotchisthenvariedinacontrolledmanner,forexample,usingalow-frequencyoscillator,ormanuallywithafootcontrol.Thestrongphaseshiftsthatexistaroundthenotchfrequencycombinewiththephasesofthedirectsignalandcausephasecancellationsorenhancementsthatsweepupanddownthefrequencyaxis.AtypicaloverallrealizationofthiseffectisshowninFig.8.2.12.Multi-notchfilterscanalsobeused.Theeffectissimilartoflanging,exceptthatinflangingthesweepingnotchesareequallyspacedalongthefrequencyaxis,whereasinphasingthenotchescanbeunequallyspacedandindependentlycontrolled,intermsoftheirlocationandwidth.Themagnitudeandphaseresponsesofatypicalsingle-notchfilterareshowninFig.8.2.13.NotethatthephaseresponseargH(ω)remainsessentiallyzero,exceptinthevicinityofthenotchwhereithasrapidvariations.InSection6.4.3,wediscussedsimplemethodsofconstructingnotchfilters.ThebasicideawastostartwiththenotchpolynomialN(z),whosezerosareatthedesirednotchfrequencies,andplacepolesbehindthesezerosinsidetheunitcircle,atsomeradialdistanceρ.Theresultingpole/zeronotchfilterwasthenH(z)=N(z)/N(ρ?1z).Suchdesignsaresimpleandeffective,andcanbeusedtoconstructthemulti-notchfilterofaphaseshifter.Choosingρtobenearunitygivesverynarrownotches.However,wecannothavecompleteandseparatecontrolofthewidthsofthedifferentnotches. Adesignmethodthatgivesprecisecontroloverthenotchfrequencyandits3-dBwidthisthebilineartransformationmethod,tobediscussedindetailinChapter11.Usingthismethod,asecond-ordersingle-notchfiltercanbedesignedasfollows:(8.2.22)wherethefilterparameterbisexpressibleintermsofthe3-dBwidthΔω(inunitsofradianspersample)asfollows:(8.2.23)TheQ-factorofanotchfilterisanotherwayofexpressingthenarrownessofthefilter.Itisrelatedtothe3-dBwidthandnotchfrequencyby:(8.2.24)Thus,thehighertheQ,thenarrowerthenotch.Thetransferfunction(8.2.22)isnormalizedtounitygainatDC.ThebasicshapeofH(z)isthatofFig.8.2.13.Because|H(ω)|isessentiallyflatexceptinthevicinityofthenotch,severalsuchfilterscanbecascadedtogethertocreateamulti-notchfilter,withindependentlycontrollednotchesandwidths.Asanexample,considerthedesignofanotchfilterwithnotchfrequencyω0=0.35π,forthetwocasesofQ=3.5andQ=35.Thecorresponding3-dBwidthsareinthetwocases:和ThefiltercoefficientsarethencomputedfromEq.(8.2.23),givingthetransferfunctionsinthetwocases:Thesubjectofadaptivesignalprocessing[27]isalsobasedonfilterswithtimevaryingcoefficients.Thetimedependenceofthecoefficientsisdeterminedbycertaindesigncriteriathatforcethefiltertoadjustandoptimizeitselfwithrespecttoitsinputs.Theimplementationofanadaptivealgorithmisobtainedbyaugmentingthesampleprocessingalgorithmofthefilterbyaddingtoitthepartthatadjuststhefilterweightsfromonetimeinstanttothenext[28].Adaptivesignalprocessinghaswidespreadapplications,suchaschannelequalization,echocancellation,noisecancellation,adaptiveantennasystems,adaptiveloudspeakerequalization,adaptivesystemidentificationandcontrol,neuralnetworks,andmanyothers.8.2.3DigitalReverberationThereverberationofalisteningspaceistypicallycharacterizedbythreedistincttimeperiods:thedirectsound,theearlyreflections,andthelatereflections[115–151],asillustratedinFig.8.2.15.Thesoundqualityofaconcerthalldependsonthedetailsofitsreverberationimpulseresponse,whichdependsontherelativelocationsofthesoundsourceandthelistener.Therefore,simulatingdigitallythereverbcharacteristicsofanygivenhallisanalmostimpossibletask.Asacompromise,digitalreverbprocessorsattempttosimulateatypicalreverberationimpulseresponseofahall,andgivetheusertheoptionoftweakingsomeoftheparameters,suchasthedurationoftheearlyreflections(thepredelaytime),ortheoverallreverberationtime.Otherinterestingreverbeffectscanbeaccomplisheddigitallythataredifficultorimpossibletodobyanalogmeans.Forexample,gatedreverbisobtainedbytruncatingtheIIRresponsetoanFIRone,asshowninFig.8.2.16,withauser-selectablegatetime.TheplainreverbfiltershowninFig.8.2.6istoosimpletoproducearealisticreverberationresponse.However,assuggestedbySchroeder[143],itcanbeusedasthebuildingblockofmorerealisticreverbprocessorsthatexhibitthediscreteearlyreflectionsandthediffuselateones.InmostapplicationsofDSP,weareinterestedinthesteadystateresponseofourfilters.Reverberationisanexception.Here,itisthetransientresponseofahallthatgivesititsparticularreverberationcharacteristics.Thesteady-stateproperties,however,dohaveaneffectontheoverallperceivedsound.Thepeaksinthesteady-statespectrumoftheplainreverbfilterofEq.(8.2.12),showninFig.8.2.7,tendtoaccentuatethosefrequenciesoftheinputsignalthatarenearthepeakfrequencies.Topreventsuchcolorationoftheinputsound,Schroederalsoproposed[143]anallpassversionoftheplainreverberatorthathasaflatmagnituderesponseforallfrequencies:(8.2.25)IthasI/Odifferenceequation:(8.2.26)Itsfrequencyandmagnituderesponsesareobtainedbysettingz=ejω:(8.2.27)ThemagnituderesponseisconstantinωbecausethenumeratoranddenominatorofH(ω)havethesamemagnitude,ascanbeseenfromthesimpleidentity:Figure8.2.17showsthecanonicalrealizationofEq.(8.2.25)realizedbyacommondelayz?D.ItalsoshowstheparallelrealizationofEq.(8.2.28),whichwasSchroeder’soriginalrealization[143].Theplainandallpassreverberatorunitscanbecombinedtoformmorerealisticreverbprocessors.Schroeder’sreverberator[143,115,119,137,127,139]consistsofseveralplainunitsconnectedinparallel,whicharefollowedbyallpassunitsincascade,asshowninFig.8.2.18.Theinputsignalcanalsohaveadirectconnectiontotheoutput,butthisisnotshowninthefigure.專業(yè)名詞術語總結flanging凸緣compression壓縮equalization均衡instrument儀器timedelay延時linearinterpolation線性插值relativesidelobelevel相對旁瓣水平physicalfrequencyresolution物理頻率分辨率computationalfrequencyresolution計算頻率分辨率resolvabilitycondition可分辨條件computationaloverhead額外的計算開銷PhaseShifting調相Narrownotchfilter窄帶陷狀濾波器Directsound源信號Single-notchfilter單陷點濾波器Magnitudesquared幅頻響應Phaseresponses相位響應prototype原型linearphase線性相位guaranteesability保證穩(wěn)定性lowpass低通highpass高通bandpass帶通bandstop帶阻transitionband過渡帶passband通帶zeropadding補零biasingerror偏移誤差roundingerror舍入誤差matrixform矩陣形式twiddlefactor旋轉因子modulo-N模NFFT(fastFouriertransform)快速傅立葉變換shuffling重排bitreversal碼位倒置fastconvolution快速卷積zero-meanwhiteGaussiannoise零均值高斯白噪聲minimizing最小化attenuation衰減transferfunction傳遞函數(shù)impulse沖激alter改變maximizing最大化piece-wiselinear分段線性time-windowing時域加窗finite-duration有限長samplingrate采樣率samplingtimeinterval采樣間隔rectangularwindow矩形窗hammingwindow漢明窗windowfunction窗函數(shù)frequencyleakage頻率泄露mainlobe主瓣sidelobe旁瓣mainlobewidth主瓣寬度relativesidelobelevel相對旁瓣水平physicalfrequencyresolution物理頻率分辨率computationalfrequencyresolution計算頻率分辨率resolvabilitycondition可分辨條件computationaloverhead額外的計算開銷exponentiallydecayingsinusoid包絡按指數(shù)衰減的正弦波wavetablesynthesis波表合成periodicsequence周期序列periodicwaveformgenerator周期波形產生器