7. Auditory - Sound pressure waves generated by vibrating...

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Sound –pressure waves generated by vibrating air molecules Amplitude (Db) = loudness Frequency or cycles/second (Hz) = pitch Humans can detect sounds in the frequency range from ~20Hz to 20kHz Most sounds consist of acoustically complex waveforms –inner ear acts like an acoustical prism, decomposing complex sounds into a myriad of constituent tones -speech is concentrated ~3kHz -some species of bats 100kHz
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Sound Acquisition
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Functions to match the low-impedance airborne sounds to the higher-impedance fluid of the inner ear. Boosts the pressure measured at the tympanic membrane ~200- fold by the time it reaches the inner ear. ( P = F/A )
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The Cochlea Energy from sonically generated pressure waves is transformed into neural impulses Organ of Corti sits on basilar membrane contains the auditory receptor neurons Scala vestibuli and scala tympani –perilymph, similar to CSF low K + , High Na + Scala media –endolymph, ionic concentration similar to intracellular fluid, low Na + , High K +
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Cochlear Physiology Helicotrema –hole in the apex basilar membrane that connects the two scala Basilar membrane widens towards the apex Stiffness of membrane decreases from base to apex Base 100x stiffer The fluid movement bends basilar membrane at base that sets up a wave that travels toward the apex Sound frequency determines the distance the wave travels up the basilar membrane
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Cochlear Physiology
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