Exam 1 Monday, Tuesday, Wednesday next week WebCT testing centre Covers everything up to and including hearing (i.e. this lecture)

Exam 1 Karla will host a review session –PE250 –3:00 to 4:00 Friday February 4 –Bring specific questions to ask

Exam 1 Matching Multiple Choice –Select the one best answer

Exam 1 True/False and Yes/No: –be sure to select true or false (or yes or no) for each answer. –Note that “yes” doesn’t mean “true”, it just means “yes”.

Upcoming Reading Assignment Read article by Gregory in your coursepack for February 10 th Read article by Pinker in your coursepack for February 17 th

Seeing Sound with Spectrograms A spectrogram is a 3D plot of sound Time Frequency

Seeing Sound with Spectrograms A spectrogram is a 3D plot of sound Time Frequency Intensity Intensity is often coded by colour such that red or black is high and blue or white is low

The Perception of Speech

Speech is for rapid communication Speech is composed of units of sound called phonemes –examples of phonemes: /ba/ in bat, /pa/ in pat Speech

Speech can be characterized by a spectrogram Acoustic Properties of Speech

Spectrogram reveals differences between phonemes The differences are in the formants and the formant transitions Acoustic Properties of Speech

Perceiving Speech So perceiving (interpreting) speech sounds is simply a matter of matching the spectrotemporal properties (the shape of the spectrogram) of the incoming sound waves to the appropriate phoneme right?…

Perceiving Speech So perceiving (interpreting) speech sounds is simply a matter of matching the spectrotemporal properties (the shape of the spectrogram) of the incoming sound waves to the appropriate phoneme Then specific phonemes must correspond to specific spectrograms - a property called acoustic-phonetic invariance

Acoustic - Phonetic invariance says that phonemes should match one and only one pattern in the spectrogram –This is not the case! For example /d/ followed by different vowels: Perceiving Speech

Acoustic - Phonetic invariance says that phonemes should match one and only one pattern in the spectrogram –This is not the case! For example /d/ Clearly perception and understanding of speech sounds is more elaborate than simply interpreting an internal spectrogram Perceiving Speech

The phrase “Peter buttered the burnt toast” has five /t/ phonemes. There are not 5 identical sweeps in the spectrogram Perceiving Speech

The Segmentation Problem Segmentation is the perception of silence between words Often illusory Perceiving Speech

The phrase “I owe you a Yo-Yo” has no silence in it ! Perceiving Speech

Spoken Input The Segmentation Problem: –The stream of acoustic input is not physically segmented into discrete phonemes, words, phrases, etc. –Silent gaps don’t always indicate (aren’t perceived as) interruptions in speech

Spoken Input The Segmentation Problem: –The stream of acoustic input is not physically segmented into discrete phonemes, words, phrases, etc. –Continuous speech stream is sometimes perceived as having gaps

Perceiving Speech So how do you perceive speech? Some of the “strategies”: 1. reduce the data 2. use context clues 3. use vision

Categorical Perception is a phenomenon in which the brain assigns a stimulus into one or another category but never into an intermediate category Categorical Perception

For example, /ba/ and /pa/ differ in their formant transitions –/ba/ is formed by stopping the flow of air from the lungs and releasing it after about 10 milliseconds (called voice onset time) –/pa/ is similar except that voice onset time is about 50 ms Categorical Perception

Voice onset time can range from zero to >50 ms. For example, you could synthesize a sound with a voice onset time of 30 ms but... Categorical Perception

Voice onset time can range from zero to >50 ms. For example, you could synthesize a sound with a voice onset time of 30 ms but... English speakers will hear either /ba/ or /pa/ but never something in between Categorical Perception

Categorical Perception is Part of Learning a Language Babies can discriminate /ba/ from /pa/ and can discriminate these from phonemes with intermediate voice onset times! By 10 to 12 months, babies (learning English) stop discriminating intermediate voice onset times

Categorical Perception is Part of Learning a Language Once category boundaries are learned it is impossible to unlearn them –non-native speakers of any language often cannot hear certain phonemes the way native speakers do –as a consequence they will always have at least some slight accent

Another example: Categorical Perception

Perception (of all types) Makes Use of Context The stream of information contained in speech is usually ambiguous and incomplete Your brain makes a “best guess” based on the circumstances

Perception (of all types) Makes Use of Context Consider the following example: “The __eel fell of the cough shoe”. car”.

Perception (of all types) Makes Use of Context Consider the following example: Listeners report hearing the “appropriate” phoneme during the cough “The __eel fell of the cough shoe”. car”.

Why rely on only one sensory system when there is information in two !? Much of Speech Perception isn’t Auditory !

Why rely on only one sensory system when there is information in two !? The brain seamlessly integrates any information it is given - this is called cross- modal integration Much of Speech Perception isn’t Auditory !

Speech perception involves the synthesis of vision and hearing The McGurk effect demonstrates the critical role of vision on speech perception Cross-modal Integration

The McGurk Effect Cross-modal Integration

The McGurk Effect - suggests that visual and auditory information are combined to enhance speech perception under normal circumstances When visual and auditory information are incongruous the resulting perception is unpredictable and often wrong Cross-modal Integration

Next Time: Taste Smell Touch Balance