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Speech Perception

demonstrations -speech synthesis & analysiscategorical perception

discrimination functionsidentification functions

discriminability = identifiability

speech production -- source-filter theoryspectrum & spectrogram

harmonicsformants

infant & infrahuman perception of speechhabituation & dishabituation

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speech demos:

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source

filter

Instrumentsto changeshape of filter

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speech stream:

vowels: monophthongs: /i/ /a/ /u/, etc.diphthongs: /ei/ /oi/, etc.

consonants:

stops: prevoiced: --

voiced: /b/ /d/ /g/

voiceless: /p/ /t/ /k/ /?/

liquids:voiced /l/ /r/ voiceless: --

fricatives: voiced: /v/ /z/// , etc.voiceless: /f/ /s/// //, etc.

clicks: -- /!/

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modified from text

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harmonic structurefrom source,sawtoothwaveform

vocal folds/glottis

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Upper harmonics are integermultiples of the fundamentalfrequency

schematization of malesource

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testosteronetarget inpuberty

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schematization of femalesource, sawtooth wave of higherfrequency

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Chas. Hockett:

The speech stream is like smashed Eastereggs

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demo

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categorical perception:

two types of results (for adults)

identification task

discrimination task

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method ofconstant

stimuli:identification

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discrimination task:

stimuli correct response| analog to 2x2cellsresponse stimuli

1-1 same

same|same correct rejection

3-3 samedifferent|same false alarm

1-3 different

different|different hit

3-1 different

same|different miss

same for pairs 2-4, 3-5, 4-6, and 5-7

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same-differentdiscrimination:

signaldetection task

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Peak of discriminationfunction at the cross-over point of theidentification functions

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baseline

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/ba/

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habituation

to /ba/change in

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habituation

habituation to /ba/

control

condition #1

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dishabituationto /da/

experimentalcondition

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lack ofdishabituation to a

different /ba/

control

condition #2

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infants discriminate /ba/-/da/ like adults do

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[b][d] [g][k] [r][l]

adults w/ yes

adults w/o ---infants yes

rhesus

chinchilla

categorical perception tally

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[b][d] [g][k] [r][l]

adults w/ yes yes yes

adults w/o --- yes noinfants yes yes yes

rhesus yes ~yes no

chinchilla ~yes no no

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Human speech perception takes advantage of what arelikely to have been pre-existing, anisomorphic notches

in the auditory systems capacity to discriminate

information.

Our own evolution may also have created new notches

Why is this a good thing?

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speech perception has to be fast.

speaking rate up to ~300 wpm

at 4 phonemes/word~20 phonemes/sec

categorical perception is a way of making rapid

decisions, throwing away unneeded (withinphoneme category) information

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lips, jaw, tongue,and pharynx foreating, etc.

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for speechproduction

Left

hemisphere

for speechandlanguageperception

Speech Perception

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Speech Perception

demonstrations -

speech synthesis & analysiscategorical perception ---> speed

& cortical areas

discrimination functionsidentification functions

discriminability = identifiability

speech production -- source-filter theory -->corticalareas

spectrum & spectrogramharmonicsformants

infant & infrahuman perception of speech

h bi i & di h bi i i f t d t