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Audition: Sound, the Ear, the Brain Psyc 351

Functional Utility of Sound. Carries information helpful for locating where things are, where you are (outside, in a large room, on firm ground, etc.)Carries information good for identification (we can identify friends from their footfalls)Travels well in air (not that quickly, and with echoes and reflections, but overall does well).

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Audition: Sound, the Ear, the Brain Psyc 351

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    1. Audition: Sound, the Ear, & the Brain Psyc 351

    2. Functional Utility of Sound Carries information helpful for locating where things are, where you are (outside, in a large room, on firm ground, etc.) Carries information good for identification (we can identify friends from their footfalls) Travels well in air (not that quickly, and with echoes and reflections, but overall does well)

    3. The nature of sound

    4. Amplitude, Frequency, Phase

    5. The nature of sound

    8. Sounds in the natural environment

    9. Fourier analysis

    10. Fourier analysis

    11. Fourier Synthesis

    12. Representations: amplitude waveforms vs. spectrographs

    13. Amplitude: The Decibel scale A ratio scale referenced to the classical threshold of human hearing, nominally .0002 dynes/cm2 (Factoid: dyne = force needed to accelerate 1g to 1cm/sec in 1 sec A logarithmic scale converts multiplicative changes to additive changes Thus, db = 20 x log (P1/P0) in sound pressure level, where P0 = .0002 dynes/cm2

    14. Amplitude Range

    15. Frequency: cycles/sec, or Hertz (Hz, from German physicist Heinrich Hertz) Middle C on piano ~ 261.6 Hz http://en.wikipedia.org/wiki/Piano_key_frequencies

    16. Frequency

    17. Frequency Range for Human Hearing Nominally 20 – 20KHz

    18. Normal vs. Impaired Hearing

    19. Comparative Hearing

    20. Phase The relative positions/timing of two waves matched for db, Hz

    21. Phase Cone: without turning your head, you cannot distinguish well the locations on the cone because they present the same three differences to the two ears.Cone: without turning your head, you cannot distinguish well the locations on the cone because they present the same three differences to the two ears.

    22. The Ear versus the Eye Orientation Attention Speed Sensitivity Echoes Eye: 400 – 700 nm, trichromaticity Ear: 20-20k Hz. “Tri- tonaticity”? No…

    23. Structure of the ear Outer structures (pinna) Inner structures: Auditory canal Tympanic membrane, acoustic reflex Ossicles: Malleus, Incus, Stapes Oval window Cochlea, basilar membrane, Organ of Corti Cilia: inner vs. outer hair cells Mechanism of transduction Impedance matching: 30 db loss

    24. The Ear, starting from the outside

    25. The Ear in cross-section

    26. The Ear in cross-section

    28. Middle Ear

    31. Dynamics of the middle ear http://funsan.biomed.mcgill.ca/~funnell/OpenHouse96/me_anim.html

    32. The Cochlea

    35. Basilar Membrane

    36. Hair Cells, outer and inner

    37. Mouse Organ of Corti (courtesy of Audrey Nath and Jeff Triffo)

    38. Brain Pathways for audition

    39. Auditory Tuning Curves

    40. More Auditory Tuning Curves

    41. Tonotopic Map of Monkey Auditory Cortex

    42. Inner Ear Summary

    43. Coding mechanisms Place theory: coding frequency and amplitude Volley principle: large numbers of detectors Periodicity coding: frequency and amplitude Duplicity theory: 1 KHz to 4 KHz Missing fundamental, masking

    44. Pathways and Brain Mechanisms Cochlear nucleus Superior olive Inferior colliculus Medial geniculate Auditory cortex Tonotopic mapping Tuning curves for "tone detectors" Detectors: tone, onset/offset, sweep

    45. Psychophysics Basic audiogram (repeat from earlier in semester) Masking, critical band

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