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Exam 1

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Exam 1

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

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

  3. Exam 1 • Matching • Multiple Choice • Select the one best answer

  4. 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”.

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

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

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

  8. The Perception of Speech

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

  10. Acoustic Properties of Speech • Speech can be characterized by a spectrogram

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

  12. 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?…

  13. 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

  14. 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/ followed by different vowels:

  15. 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

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

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

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

  19. 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

  20. 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

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

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

  23. 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

  24. 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...

  25. 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

  26. 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

  27. 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

  28. Categorical Perception • Another example:

  29. 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

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

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

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

  33. 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

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

  35. Cross-modal Integration • The McGurk Effect

  36. 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

  37. Next Time: Taste Smell Touch Balance