Lecture_14 - Auditory Systems The detection of sound Sound...

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The detection of sound Sound waves (fig11.1) -Compressed air: it becomes more dense -Rarefied air: it becomes less dense Measured in frequency (Hz) and intensity fig 11.2 - Frequency = pitch: distance of period - Intensity = volume distance from peak to trough The Ear (fig 11.3) Outer: - Pinna - external portion: acts as a funnel to bounce sound waves into canal - Auditory canal : channels sound waves Middle: - Tympanic membrane and 3 ossicles : connected to nasal cavity (Eustachian tube) Inner: - Cochlea : coiled tube, connected to middle by oval window, also round window is here - Semicircular tubes - Once neural response to sound is generated in the inner ear the signal is transferred to and processed by a series of nuclei. Then the output from these nuclei is sent to a relay in the thalamus MGN which sends it to the primary auditory cortex MIDDLE EAR - 3 Ossicles - Malleus, Incus, Stapes: -take sound waves and turn them into mechanical movement to amplify force of sound waves and concentrate force from big tympanic membrane to small oval window - Attenuation by Muscles : Tensor Tympani muscle and stapedius muscle - Reflex action - muscles retract and resist movement of ossicles, reducing force on the oval window -sound attenuation is greater at lower frequencies than higher frequencies -doesn’t protect against sudden loud noise - Eustacian tube : allows the air in the middle ear to be continuous with the air in he nasal cavity INNER EAR - Cochlea (cross section unrolled fig 11.7 & 11.8) - fluid (perilymph) filled chambers : Scala vestibuli and Scala tympani are connected by hole helicotrema -fluid can pass through each chamber by the helicotrema -Round window bulges as a pressure valve when fluid is disrupted - Basilar membrane is moved up and down when fluid is disrupted. -
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This note was uploaded on 04/28/2008 for the course ZOL 402 taught by Professor Eisthen during the Fall '05 term at Michigan State University.

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Lecture_14 - Auditory Systems The detection of sound Sound...

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