最新acoustic-phonetics教学讲义ppt课件.ppt

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1、acoustic-phoneticsAcousticparametersFundamentalfrequency(F0:Hz)Pitch(auditory)Amplitude(dB)Loudness(auditory)Formants:frequenciesaboveF0(Hz)Quality(auditory)DifferentqualitybetweenvowelAandvowelBdifferentformantpatternsLength:Duration(s)Speechsoundconsists

2、ofsmallvariationsinairpressurewhichareaudiblebtw20to20,000perturbations/Hz.Everytimethevocalcordsopenandclose,thereisapulseofairfromthelungs.Inthecaseofvoicedsounds,thevibratingvocalcordschopupthestreamoflungairsothatpulsesofhighpressurealternateswithpulsesof

3、lowerpressure.Whenvariationsinairpressureintheformofsoundwavesreachtheearofthelistener,theycausetheeardrumtovibrate.PropertiesofSineWaveThissimplestkindofwaveisoftencalledasinewave.CombiningWavesIfyou'relisteningtowavesfromtwosourcesatthesametime:ahighpressur

4、efromonesourcewilltendtocanceloutalowpressurefromtheother;twohighpressureswillreinforceeachotherandcreateanevenhigherpressure;twolowerpressureswillreinforceeachotherandcreateanevenlowerpressureAnycomplexwavecanbetreatedasacombinationofsimplesinewaves.Formostp

5、racticalpurposesinphonetics,wedon'tcareabouttheactualcomplexwaveformitself.We'reonlyinterestedinthefrequenciesandamplitudesofthesimplewavesthatit'smadeof.(a),(b),(c)arecomponentfrequencies,and(d)isacomplexwaveform.Whenthesignal(sound)isperiodic,thesinewavesi

6、nthecomplexwavesarewhole-numbermultiples(整倍数)ofthesamefundamentalfrequency(F0).Whenthesignalisnoise(aperiodic),thefrequenciesofthesinewaveshavenorelationship(无比例关系)tooneanother.Analysisofacomplexsoundiscalledspectralanalysis.Wavelength:thelengthofasoundwaveis

7、thedistanceinspacethatonecycleoccupies.Onecanmeasurefromanypointinonecycletothecorrespondingpointinthenextcycle.Highfrequencysoundsoccupylessspacepercycle,haveashorterwavelength,thandolowfrequencysounds.PitchandFrequencyFrequencyisthenumberofthecompleterepeti

8、tions(cycles)ofwaveforms(orthenumberofvibrations)inasecond.TheunitoffrequencyismeasuredinHz.Ifthevocalcordsmake200completeopeningandclosingmovementsinasecond,thefrequencyis200Hz.Soitispos