Outline Speech Perception - Nazareth College
Transcript of 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