acoustic phonetics

BriefIntroductiontoAcousticPhoneticsHuiqinMaSep15,2010•Acousticparameters•Fundamentalfrequency(F0:Hz)Pitch(auditory)•Amplitude(dB)Loudness(auditory)•Formants:frequenciesaboveF0(Hz)Quality(auditory)•DifferentqualitybetweenvowelAandvowelBdifferentformantpatterns•Length:Duration(s)•Speechsoundconsistsofsmallvariationsinairpressurewhichareaudiblebtw20to20,000perturbations/Hz.•Everytimethevocalcordsopenandclose,thereisapulseofairfromthelungs.•Inthecaseofvoicedsounds,thevibratingvocalcordschopupthestreamoflungairsothatpulsesofhighpressurealternateswithpulsesoflowerpressure.•Whenvariationsinairpressureintheformofsoundwavesreachtheearofthelistener,theycausetheeardrumtovibrate.Soundwave•Soundiscausedbyperturbationofairpressure,itisanalternatingpatternofhighandlowpressureareas.Theredlinerepresentstheaveragebackgroundairpressure--theairpressurethatwouldexistiftherewerenosoundwaves.Pointsabovethislinerepresenthigherpressure(morecrowdedairmolecules);pointsbelowrepresentlowerpressure(lesscrowdedairmolecules).ThewaveformshowsspeechasafunctionofAmplitude(whichismeasuredindecibels(dB),andthefrequencyofthesoundwavesmeasuredinhertz(Hz).PropertiesofSineWave•Thissimplestkindofwaveisoftencalledasinewave.CombiningWaves•Ifyou'relisteningtowavesfromtwosourcesatthesametime:•ahighpressurefromonesourcewilltendtocanceloutalowpressurefromtheother;•twohighpressureswillreinforceeachotherandcreateanevenhigherpressure;•twolowerpressureswillreinforceeachotherandcreateanevenlowerpressure•Anycomplexwavecanbetreatedasacombinationofsimplesinewaves.•Formostpracticalpurposesinphonetics,wedon'tcareabouttheactualcomplexwaveformitself.We'reonlyinterestedinthefrequenciesandamplitudesofthesimplewavesthatit'smadeof.(a),(b),(c)arecomponentfrequencies,and(d)isacomplexwaveform.•Whenthesignal(sound)isperiodic,thesinewavesinthecomplexwavesarewhole-numbermultiples(整倍数)ofthesamefundamentalfrequency(F0).•Whenthesignalisnoise(aperiodic),thefrequenciesofthesinewaveshavenorelationship(无比例关系)tooneanother.•Analysisofacomplexsoundiscalledspectralanalysis.•Wavelength:thelengthofasoundwaveisthedistanceinspacethatonecycleoccupies.•Onecanmeasurefromanypointinonecycletothecorrespondingpointinthenextcycle.•Highfrequencysoundsoccupylessspacepercycle,haveashorterwavelength,thandolowfrequencysounds.PitchandFrequencyFrequencyisthenumberofthecompleterepetitions(cycles)ofwaveforms(orthenumberofvibrations)inasecond.TheunitoffrequencyismeasuredinHz.Ifthevocalcordsmake200completeopeningandclosingmovementsinasecond,thefrequencyis200Hz.Soitispossibletodeterminethefrequencyofasoundbycountingthepeaksofairpressureinarecordofitswaveforms.Frequencydeterminespitch.Whenaspeechsoundgoesupinfrequency,italsogoesupinpitch,therateofspeechalsogoesup.ThepitchofasoundmaybeequatedwithitsfundamentalfrequencyFundamentalfrequency(基频）E1):determinedbyhowmanytimesthevocalfoldsvibrateinonesecond(ifthevocalcordsopenandclose100timespersecond,theglottalperiodequals10millisecond,theF0equals100Hz);E2):firstharmonic,fundamental.•F0(readasFnaughtorFzero)isofparticularimportanceinstudiesofintonation.•F0determinestone.Toneisconnectedwithpitchvariations.Weperceivetones.•Pitch:Vowelshavean‘intrinsic’pitchwhichcorrelateswithvowelheight:•highvowelshavehighpitch•andlowvowelshavelowpitch,•andthedifferencecanbeaslargeas20-25Hz.•Pitchpatternsareeithersteady,risingorfalling,anditischangingpitchthathasagreaterperceptualsalience.•Aspeakertakeslesstimetoproduceafallingpitchthanarisingpitch.•Alllanguagesvarypitchtoconveylinguisticinformation.Amplitude/Intensity/Loudness•Amplitudedeterminesloudness.•Theloudnessofasounddependsonthesizeofthevariationsinairpressure(oramplitude).•Acousticintensityistheappropriatemeasurecorrespondingtoloudness(measuredindB).Spectrogramcantellushowmuchacousticenergyisproduced.•Intensityisaphysicalcharacteristicofasound,andloudnessisthesubjectivepropertyofasoundthatismostdirectlyrelatedtointensity.Resonance(共鸣频率)•Resonance(共鸣频率):Aresonatorissomethingthatissetintoforcedvibrationbyanothervibration.•Inspeech,theresonancesofthevocaltractarecalledformantfrequenciesorsimplyformants.Theresonantfrequenciesdependontheshapeandsizeofthevocaltract.Vocalfoldsvibration-harmonics,H1(F0),H2,H3…-Oral,nasal,andpharyngealcavities-toformresonators-Differentshapes/sizesoftheresonators-resonateandemphasizecertainharmonics-formants(F1,F2,F3)-Formantpatterns-qualityofsounds(vowels/sonorants)Formants(共振峰）•Aformantisaconcentrationofacousticenergy,reflectingthewayairfromthelungsvibratesinthevocaltract.•Inwidebandspectrogram（0.005),formantsshowupasagroupofdarkenergybands;•innarrow-bandspectrogram(0.025),formantsshowupasagroupofadjacentharmonics.•Sowide-bandisbetterinviewingformants,whilenarrow-bandisbetterforviewingharmonics.•Formantsarenumbered.•Vowelsarecharacterizedbythreeformants:F1,F2,F3.•ThechangeofF1andF2meansthechangeofavowel.•Vowelheight-F1,•Thehigheravowel,thelesstheF1•backness-F2-F1•ThelargerthenumberofF2-F1,themoreforwardthevowelStoptransition&placeofarticulation•Eg_a_stop_a/i_stop_i•adjacenttoalabialstop,