acoustic-phoneticsPPT课件

-,1,BriefIntroductiontoAcousticPhoneticsHuiqinMaSep15,2010,-,2,AcousticparametersFundamentalfrequency(F0:Hz)Pitch(auditory)Amplitude(dB)Loudness(auditory)Formants:frequenciesaboveF0(Hz)Quality(auditory)DifferentqualitybetweenvowelAandvowelBdifferentformantpatternsLength:Duration(s),-,3,Speechsoundconsistsofsmallvariationsinairpressurewhichareaudiblebtw20to20,000perturbations/Hz.Everytimethevocalcordsopenandclose,thereisapulseofairfromthelungs.Inthecaseofvoicedsounds,thevibratingvocalcordschopupthestreamoflungairsothatpulsesofhighpressurealternateswithpulsesoflowerpressure.Whenvariationsinairpressureintheformofsoundwavesreachtheearofthelistener,theycausetheeardrumtovibrate.,-,4,Soundwave,Soundiscausedbyperturbationofairpressure,itisanalternatingpatternofhighandlowpressureareas.,-,5,Theredlinerepresentstheaveragebackgroundairpressure-theairpressurethatwouldexistiftherewerenosoundwaves.Pointsabovethislinerepresenthigherpressure(morecrowdedairmolecules);pointsbelowrepresentlowerpressure(lesscrowdedairmolecules).,-,6,ThewaveformshowsspeechasafunctionofAmplitude(whichismeasuredindecibels(dB),andthefrequencyofthesoundwavesmeasuredinhertz(Hz).,-,7,PropertiesofSineWave,Thissimplestkindofwaveisoftencalledasinewave.,-,8,CombiningWaves,Ifyourelisteningtowavesfromtwosourcesatthesametime:ahighpressurefromonesourcewilltendtocanceloutalowpressurefromtheother;twohighpressureswillreinforceeachotherandcreateanevenhigherpressure;twolowerpressureswillreinforceeachotherandcreateanevenlowerpressure,-,9,Anycomplexwavecanbetreatedasacombinationofsimplesinewaves.Formostpracticalpurposesinphonetics,wedontcareabouttheactualcomplexwaveformitself.Wereonlyinterestedinthefrequenciesandamplitudesofthesimplewavesthatitsmadeof.,-,10,(a),(b),(c)arecomponentfrequencies,and(d)isacomplexwaveform.,-,11,Whenthesignal(sound)isperiodic,thesinewavesinthecomplexwavesarewhole-numbermultiples(整倍数)ofthesamefundamentalfrequency(F0).Whenthesignalisnoise(aperiodic),thefrequenciesofthesinewaveshavenorelationship(无比例关系)tooneanother.Analysisofacomplexsoundiscalledspectralanalysis.,-,12,Wavelength:thelengthofasoundwaveisthedistanceinspacethatonecycleoccupies.Onecanmeasurefromanypointinonecycletothecorrespondingpointinthenextcycle.Highfrequencysoundsoccupylessspacepercycle,haveashorterwavelength,thandolowfrequencysounds.,-,13,PitchandFrequency,Frequencyisthenumberofthecompleterepetitions(cycles)ofwaveforms(orthenumberofvibrations)inasecond.TheunitoffrequencyismeasuredinHz.Ifthevocalcordsmake200completeopeningandclosingmovementsinasecond,thefrequencyis200Hz.,-,14,Soitispossibletodeterminethefrequencyofasoundbycountingthepeaksofairpressureinarecordofitswaveforms.Frequencydeterminespitch.Whenaspeechsoundgoesupinfrequency,italsogoesupinpitch,therateofspeechalsogoesup.Thepitchofasoundmaybeequatedwithitsfundamentalfrequency,-,15,Fundamentalfrequency(基频）,E1):determinedbyhowmanytimesthevocalfoldsvibrateinonesecond(ifthevocalcordsopenandclose100timespersecond,theglottalperiodequals10millisecond,theF0equals100Hz);E2):firstharmonic,fundamental.,-,16,F0(readasFnaughtorFzero)isofparticularimportanceinstudiesofintonation.F0determinestone.Toneisconnectedwithpitchvariations.Weperceivetones.,-,17,Pitch:Vowelshaveanintrinsicpitchwhichcorrelateswithvowelheight:highvowelshavehighpitchandlowvowelshavelowpitch,andthedifferencecanbeaslargeas20-25Hz.,-,18,Pitchpatternsareeithersteady,risingorfalling,anditischangingpitchthathasagreaterperceptualsalience.Aspeakertakeslesstimetoproduceafallingpitchthanarisingpitch.Alllanguagesvarypitchtoconveylinguisticinformation.,-,19,Amplitude/Intensity/Loudness,Amplitudedeterminesloudness.Theloudnessofasounddependsonthesizeofthevariationsinairpressure(oramplitude).,-,20,Acousticintensityistheappropriatemeasurecorrespondingtoloudness(measuredindB).Spectrogramcantellushowmuchacousticenergyisproduced.Intensityisaphysicalcharacteristicofasound,andloudnessisthesubjectivepropertyofasoundthatismostdirectlyrelatedtointensity.,-,21,Resonance(共鸣频率),Resonance(共鸣频率):Aresonatorissomethingthatissetintoforcedvibrationbyanothervibration.Inspeech,theresonancesofthevocaltractarecalledformantfrequenciesorsimplyformants.Theresonantfrequenciesdependontheshapeandsizeofthevocaltract.,-,22,Vocalfoldsvibration-harmonics,H1(F0),H2,H3-Oral,nasal,andpharyngealcavities-toformresonators-Differentshapes/sizesoftheresonators-resonateandemphasizecertainharmonics-formants(F1,F2,F3)-Formantpatterns-qualityofsounds(vowels/sonorants),-,23,Formants(共振峰）,Aformantisaconcentrationofacousticenergy,reflectingthewayairfromthelungsvibratesinthevocaltract.Inwidebandspectrogram（0.005),formantsshowupasagroupofdarkenergybands;innarrow-bandspectrogram(0.025),formantsshowupasagroupofadjacentharmonics.,-,24,Sowide-bandisbetterinviewingformants,whilenarrow-bandisbetterforviewingharmonics.Formantsarenumbered.,-,25,Vowelsarecharacterizedbythreeformants:F1,F2,F3.ThechangeofF1andF2meansthechangeofavowel.VowelheightF1,Thehigheravowel,thelesstheF1backnessF2-F1ThelargerthenumberofF2-F1,themoreforwardthevowel,-,26,Stoptransitione.g.,ifthefundamentalfrequencyis200,theharmonicswillbeat400Hz,600Hz,800HzInthisexample,400Hzwouldbethefirstharmonic,600Hzwillbethesecondharmonic,800Hzisthethirdharmonic.Harmonicimpliesperiodic,otherwiseitisaperiodic.,-,29,Distinguishharmonicswithformantfrequencies,Ifweknowthefundamentalfrequency,weknowtheharmonics.Varyingthefundamentalfrequencychangesthepitchofthevowel.Suchisnotthecasefortheformantfrequencieswhichresultfromthepositionofthetongueandtheshapeofthemouth.Whenthetongueishighandforwardinthevocaltractsuchasthevowel/i/,/i/hasthehighestF2(about2250)andlowestF1(about220).Whenthebackofthetongueishighsuchasthevowel/u/,ithasthelowerF2(about870)andhigherF1(about310)whencomparedwith/i/.,-,30,VowelNormalization(元音的规整),Men,womenandchildrendifferinvocaltractlength,thesedifferencesresultindifferencesinformantfrequenciesinproducingvowels.Theyalsodifferinthevocalfolds：femaleshaveshortervocalfoldswithlessmassthanmales,sotheytendtohavehigheraveragefundamentalfrequencies.Children,whosevocalfoldsareevenshorter,usuallyhavemuchhigherfundamentalfrequenciesthanadults.Thesephysicaldifferencesinspeakersresultinconsiderabledifferencesintheformantfrequenciesforparticularvowels.,-,31,Vowelnormalizationreferstotheperceptualprocessoffactoringoutdifferencesduetovocaltractdifferences.Infactthereisaconsiderabledegreeofoverlapofvowelspaces(元音空间有很大程度的重叠)）betweenadultsandchildren.Researchwithveryyoungchildrenhasprovidedevidencethattheyarecapableofnormalizingvowelsfordifferentspeakers(Kuhl,1987;Lieberman,1984).,-,32,Infantscanrecognizethesamevowelacrossdifferentspeakersdespitetheacousticdifferences.Researchershavesuggestedthatthiscapacity(vowelnormalization)isinnateandpresentatbirth.,-,33,VOT,Invoicedstopconsonants,thevoicingbeginsalmostsimultaneouslywhentheocclusionoftheairstreamisreleased.Incontrast,thereisadelayintheonsetofvocalfoldvibrationaftertheocclusionoftheairstreamisreleasedinthecaseofvoicelessconsonants.Thedifferencebetweenvoicedandvoicelessconsonantsisactuallyoneoftherelativetimingoftheonsetof