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Auditory Physiology 1

Auditory Physiology 1. PSY 295 – Sensation & Perception Christopher DiMattina , PhD. Hearing. What is hearing good for?. Sound. Sound. What is sound?. What is sound?. Tuning fork. Tuning fork. Sound. Any time-varying sound pressure waveform The simplest kind of sound is a pure tone.

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Auditory Physiology 1

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  1. Auditory Physiology 1 PSY 295 – Sensation & Perception Christopher DiMattina, PhD

  2. Hearing PSY 295 - Grinnell College - Fall 2012

  3. What is hearing good for? PSY 295 - Grinnell College - Fall 2012

  4. Sound PSY 295 - Grinnell College - Fall 2012

  5. Sound • What is sound? PSY 295 - Grinnell College - Fall 2012

  6. What is sound? PSY 295 - Grinnell College - Fall 2012

  7. Tuning fork PSY 295 - Grinnell College - Fall 2012

  8. Tuning fork PSY 295 - Grinnell College - Fall 2012

  9. Sound • Any time-varying sound pressure waveform • The simplest kind of sound is a pure tone 300 Hz 5000 Hz 1000 Hz PSY 295 - Grinnell College - Fall 2012

  10. Fourier analysis • Every sound can be represented as a sum of pure tones • A pure tone contains only one frequency • White noise contains all possible frequencies PSY 295 - Grinnell College - Fall 2012

  11. Fourier analysis PSY 295 - Grinnell College - Fall 2012

  12. Harmonics PSY 295 - Grinnell College - Fall 2012

  13. Measuring loudness • Loudness of a sound is measured in decibels or dB • A 10:1 SPL ratio is 20 dB, a 100:1 SPL ratio is 40 dB dB = 20 log10 (P/P0) PSY 295 - Grinnell College - Fall 2012

  14. Sound pressure ratios PSY 295 - Grinnell College - Fall 2012

  15. Intuitive loudness scale PSY 295 - Grinnell College - Fall 2012

  16. Frequency and amplitude ranges PSY 295 - Grinnell College - Fall 2012

  17. Transduction of sound PSY 295 - Grinnell College - Fall 2012

  18. Pinna • Sound is collected by the pinna of the outer ear • Acts to filter sound PSY 295 - Grinnell College - Fall 2012

  19. Many different pinna PSY 295 - Grinnell College - Fall 2012

  20. Outer ear • Pinna and ear canal gather and focus sound on tympanic membrane PSY 295 - Grinnell College - Fall 2012

  21. Middle ear • Air filled chamber with three bones connecting the tympanic membrane to the cochlea of the inner ear PSY 295 - Grinnell College - Fall 2012

  22. Ossicles • The ossicles amplify sound • Transform vibrations from large to small surface: Tympanic membrane is 18 times larger than the oval window PSY 295 - Grinnell College - Fall 2012

  23. Tensor Tympani • Muscles connected to the ossicles tense when sounds are too loud, impeding sound transmission to sensitive inner ear • Acoustic reflex (200 msec delay) PSY 295 - Grinnell College - Fall 2012

  24. Inner ear PSY 295 - Grinnell College - Fall 2012

  25. Cochlea PSY 295 - Grinnell College - Fall 2012

  26. Greek word for snail PSY 295 - Grinnell College - Fall 2012

  27. Cochlea • Spiral structure containing three fluid-filled canals • Vestibular canal and tympanic canal are contiguous and wrapped around the middle canal PSY 295 - Grinnell College - Fall 2012

  28. Basilar membrane • Basilar membrane separates tympanic from middle canal • Reissner’s membrane separates vestibular from middle canal PSY 295 - Grinnell College - Fall 2012

  29. Cochlear partition • Basilar membrane, tectorial membrane and organ of corti • Organ of corti = hair cells and auditory nerve fibers PSY 295 - Grinnell College - Fall 2012

  30. Organ of corti PSY 295 - Grinnell College - Fall 2012

  31. Basilar membrane vibrations • Vibration of oval window by the ossiclesinduces vibrations of the fluid in the tympanic canal of the cochlea • Causes vibration of the basilar membrane • Hair cells experience shear force from tectorial membrane • Opens ion channels and depolarizes hair cells PSY 295 - Grinnell College - Fall 2012

  32. Basilar membrane vibrations PSY 295 - Grinnell College - Fall 2012

  33. Hair cells PSY 295 - Grinnell College - Fall 2012

  34. Video on hair cells • http://www.youtube.com/watch?v=1VmwHiRTdVc PSY 295 - Grinnell College - Fall 2012

  35. Hair cells • Retina has 100 million photoreceptors • Cochlea has only 14,000 hair cells PSY 295 - Grinnell College - Fall 2012

  36. Hair cells • Hair cells have spiky projections called stereocilia which project into the tectorial membrane • When sterocilia bend due to shear force from tectorial membrane, ion channels open and the hair cell depolarizes PSY 295 - Grinnell College - Fall 2012

  37. Hair cells PSY 295 - Grinnell College - Fall 2012

  38. Tip links PSY 295 - Grinnell College - Fall 2012

  39. Hair cells synapse onto auditory nerve PSY 295 - Grinnell College - Fall 2012

  40. Tonotopic organization PSY 295 - Grinnell College - Fall 2012

  41. Tonotopic organization PSY 295 - Grinnell College - Fall 2012

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