Outline Speech Perception - Nazareth College

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1 11/16/11 1 Speech Perception Chapter 13 Review session Thursday 11/17 5:30-6:30pm S249 11/16/11 2 Outline Speech stimulus / Acoustic signal Relationship between stimulus & perception Stimulus dimensions of speech perception Cognitive dimensions of speech perception Speech perception & the brain 11/16/11 3 Speech stimulus Phonemes – English: 37 phonemes 13 vowel sounds 24 consonant sounds – Hawaiian: 11 phonemes – Some African dialects: 60 phonemes Phonemes (IPA – Int’l phonemic alphabet) 11/16/11 4

Transcript of Outline Speech Perception - Nazareth College

Page 1: Outline Speech Perception - Nazareth College

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Speech Perception

Chapter 13

Review session Thursday 11/17

5:30-6:30pm S249

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Outline

•  Speech stimulus / Acoustic signal

•  Relationship between stimulus & perception

•  Stimulus dimensions of speech perception

•  Cognitive dimensions of speech perception

•  Speech perception & the brain

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Speech stimulus

•  Phonemes –  English: 37 phonemes

•  13 vowel sounds •  24 consonant sounds

– Hawaiian: 11 phonemes

–  Some African dialects: 60 phonemes

Phonemes (IPA – Int’l phonemic alphabet)

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Speech production

Air from lungs

Constriction of air flow

Vibration�of vocal folds

Speech emerges

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Speech production

Why did Ken set the soggy net on top of the deck?

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Acoustic signal

•  Vowels – vibration of vocal cords and change to shape of vocal tract

–  FORMANTS - peaks in pressure at different frequencies

•  Each vowel has characteristic formants

Sound spectrogram

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Acoustic signal

•  Consonants - produced by a constriction of the vocal tract

•  Formant transitions - rapid changes in frequency preceding or following vowels

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Outline

•  Speech stimulus / Acoustic signal

•  Relationship between stimulus & perception

•  Stimulus dimensions of speech perception

•  Cognitive dimensions of speech perception

•  Speech perception & the brain

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Speech stimulus & speech perception

•  Segmentation problem

•  Variability problem – acoustic signal is so variable – Phoneme context (coarticulation) – Different speakers

Segmentation problem

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Phoneme context

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Speech stimulus & speech perception

•  Speaker variability – differ in pitch, accent, speed in speaking,

and pronunciation

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Outline

•  The speech stimulus

•  Relationship between stimulus & perception

•  Stimulus dimensions of speech perception

•  Cognitive dimensions of speech perception

•  Speech perception & the brain

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Stimulus dimensions of speech perception

•  Categorical perception – VOT (voice-onset time) & phonemic boundary

•  Speech perception is multimodal – McGurk effect

Voice onset time

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Categorical perception

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McGurk effect

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Cognitive dimensions of speech perception

•  Top-down processing

•  Segmentation affected by context & meaning

‘I scream you scream we all scream for ice cream’

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Ganong effect

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Ganong effect

Subjects shift their phoneme boundaries to favor phoneme that

makes a legal word:

peach

petal “bettle”

“pash” bash

beach 1 2 3 4 5 6 7 8

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Speech perception & the brain

•  Broca’s aphasia - frontal lobe damage –  Labored, stilted speech, and short sentences but

good comprehension

•  Wernicke’s aphasia - temporal lobe damage –  Speak fluently, but content is disorganized and not

meaningful

–  Difficulty understanding others

Speech perception & the brain

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Experience-dependent plasticity

•  < 1y.o. - infants can differentiate all phonemes

•  Brain becomes “tuned” to speech sounds in environment

•  Other sound differentiation disappears when there is no reinforcement from environment