Speech Perception 4/4/00

Basic Issues in Speech Perception Speaker Normalization Time Normalization Integration: Segmental & Suprasegmental Information Defining Units of Speech Perception Cross-Modal Aspects of Speech Perception

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

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

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

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

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

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

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

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)

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

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 36% at 24 feet