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Download Sound Waves Characteristics of Sound Waves The Outer, Middle
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11/2/2011 Book Fig. 7.3 Sound Waves Characteristics of Sound Waves Book Fig. 7.2 The Outer, Middle & Inner Ear Air Pressure Balanced for Normal Hearing Book Fig. 7.2 Book Fig. 7.2 http://www.youtube.com/watch?v=rc5GpoD8wI Sound Triggered Movements in Ear “Ossicles” Inner ear Cross section of Cochlea Auditory Auditory Nerve fibers Basilar Membrane Outer ear http://www.youtube.com/watch?v=8wgfowbbTz0 Middle ear 1 11/2/2011 Book Fig. 7.2 Organ of Corti Auditory Hair Cells Lined up on Basilar Membrane Tectorial Membrane Basilar Membrane ~ 12,000 Outer hair cells Friction on tips of hair cells opens K+ ion channels K+ enters hair cells causing depolarization & transmitter release! “Tonotopic” Relationship Between Place in Cochlea and Pitch If our inner ear is working perfectly we can hear frequencies between 20-20,000 cps “Place theory” best explains pitch perception of upper 80% of our range. ~ 4,000 Inner Hair cells Fluid Waves Traveling Thru Cochlea Cause Basilar Membrane Movement Georg von Bekesy – 1961 Nobel Prize for his research on the traveling waves in the cochlea. Where the wave peaks varies with pitch. http://www.youtube.com/watch?v=dyenMluFaUw&feature=related http://www.youtube.com/watch?v=WO84KJyH5k8&feature=related Sound Localization • Brain processes time & intensity differences in what the right & left ears hear. • Sound from right arrives sooner and louder in the right ear. 2 11/2/2011 Book Fig. 7.7 Localization • Relies on differences in what 2 ears hear to locate sounds – Intensity differences (hi freqs) – Time of onset differences (any sudden onset sound) – Phase differences (low freqs) Note: Input from each ear goes to both sides of brain but more strongly to contralateral side. Brainstem areas involved in quick sound localization and auditory reflexes. • Tell front sounds from back sounds because of pinna-related differences (sounds from front clearer and louder than sounds from back) VIII VIII (Located in superior temporal gyrus) Book Fig. 7.6 “Tonotopic” Map in cortex & cochlea Primary auditory cortex surrounded by higher level processing areas, analyzing more complex sequences or combinations of sounds. Seems to be regions devoted to what the stimulus is &where the stimulus came from. Normal & “Trampled” Hair Cells Exposed to Loud Sounds • http://www.youtube.com/watch?v=Xo9bwQuYrR o (dancing hair cell) • http://www.youtube.com/watch?v=ulAISCEQzRo • (stereocilia) 3 ERROR: undefined OFFENDING COMMAND: f‘~ STACK:
