BIOL 2P94 Lecture Notes - Olfactory Tract, Optic Disc, Icecube Neutrino Observatory
4 Feb 2013
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Document Summary
Sound is pressure waves of alternating compressions and rarefactions. Intensity is in decibels sound pressure level: db spl = 20 log [p/p0]. Huge range of sounds are encountered in the world. Human hearing spans 20 10,000 hz, with peak sensitivity at 2 khz. 90db can produce temporary threshold shift, in which sensitivity is reduced. With severe sound exposure, cochlear hair cells can be killed. Most common hearing loss is presbycusis, or loss of high frequency hearing with age. The ear canal resonates frequencies around 4 khz and enhances them. These structures help you locate the source of a sound based on frequency signatures. The middle ear bones muse overcome the acoustic impedance mismatch of air/water. Water has much higher acoustic impedance, and normally sound going from air to water is mostly reflected. The small area of the stapes footplate and lengths of middle ear bones (lever) increase the pressure wave ~26 fold.
