Transcript Speech Perception

Speech Perception
4/4/00
1
Basic Issues in Speech Perception
• Speaker Normalization
• Time Normalization
• Integration: Segmental &
Suprasegmental Information
• Defining Units of Speech Perception
• Cross-Modal Aspects of Speech
Perception
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Speaker Normalization
• Normalization needed because of differences in
acoustic measures of speech
• Women & men are biologically and acoustically
different
– How do we perceive these differences?
– This perception is present in infants:
• Can recognize the same phonetic element produced by a woman or a
man
– Word recognition performance is poorer for words from a
mixed group of talkers than for words produced by a single
talker
• Conclusion: Listeners make adjustments for different
talkers
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Speech: 4 Types of Information
• Phonetic Quality
– Linguistic content
• Affective Quality
– Paralinguistic emotional quality that accomplishes the
linguistic message
• Personal Quality
– Extralinguistic information about the talker but not the
message
• Transmittal Quality
– Perspectaval information about the talkers location,
including distance between talker & listener, orientation is
space & presence of background noise
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Time Normalization
• Different talkers speak at different rates &
different rates at different times
• Speaking rates vary because segment durations
are flexible
• Variable acceptance of different duration VOT
• Is speech intelligibility reduced for speakers
who deviate from typical temporal patterns of
normal adult speech?
– Children & disordered speech
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Integrating Segmental & Suprasegmental
Information
• Suprasegmental cues (intonation, rhythm,
& pausing) help the listener segment the
incoming message
• How is suprasegmental information used
with segmental information?
– Acoustic cues (f0, duration & intensity)
signal suprasegmental structure such as
stress & rhythm
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What is the Basic Unit of Perception?
• When we listen to speech, do we analyze it
in terms of features, phonemes, syllables
or words?
– Listeners of different ages and linguistic
competence prefer different size units
• Young children operate with syllable-sized units
• Adults extract phoneme level information
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Cross-Model Speech Perception
• Do listeners with normal hearing attend
to visual cues in speech?
– McGurk effect: This effect was produced by
studying different combinations of visual and
auditory cues
• ex. subjects would view a video tape of a
speaker saying the syllable [ba], but would hear
the acoustic signal [da]
– Subjects identified the sound as [g]: Phonetic decision
was based on a synthesis of auditory & visual cues
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Speech Perception: Infancy & Childhood
• We hear in the womb
– Early auditory experiences biases the
neonate to the mother’s voice
– By the 1st year, infants can specialize sounds
of the mother tongue
• By this age they have lost discrimination for
foreign sounds
• Auditory reorganization
• Children continue to improve basic
discrimination of frequency, intensity &
duration until age 7 years
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Speech Perception, Language,
Learning & Education
• Children are less able to discriminate
speech in noisy or reverberant
environments
• Children are more prone to some diseases
that disrupt speech perception
– Otitis Media
• ex. may not recognize VOT variation (history of
ear infections)
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Speech Perception, Language,
Learning & Education
• Speech perception difficulties contribute
to language disorders in children– Certain grammatical morphemes in English
have low “phonetic substance”
• ex. “s” in dogs or past tense marker in talked
– These morphemes are harder to hear & are difficult
to perceive
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Speech Perception, Language, Learning &
Education
• Speech perception and classroom learning– Environment not ideal:
• teacher’s speech about 6 dB more intense than
background noise
• Teacher turning head away from listener
• Typical classroom has a reverberation time of 0.45
seconds
• Distance of teacher to student
– ex. % of words heard by 5- to 7- year old children
with normal hearing with varied distance
• 89% at 6 feet
• 55% at 12 feet
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• 36% at 24 feet