[linux-audio-user] re: sampling at high frequencies

BrbrOfSvl at aol.com BrbrOfSvl at aol.com
Mon Jan 26 10:11:55 EST 2004

->Which membrane? The basilar membrane is responsible for frequency alaysis(AFAIR), but its limited by its geometry. Doesn't it detect resonances inthe narrowing tube? Transients could be detected before the pressure wavereaches the basilar membrane, though I'm just guessing here.<-
Quick review - changes in air pressure cause the eardrum to move.  This causes the three little bones (hammer, anvil, stirrup) to move - these bones are responsible for a great deal of amplification of sound which is needed when you are trying to vibrate liquid from vibrating air.  The last and smallest bone causes a little membrane on the outside of the inner ear to vibrate, which sets up vibrations in the fluid of the inner ear.  That fluid causes the basilar membrane to vibrate (the very very short-story version of this is that the basilar membrane vibrates in different places based on the frequency).  Basilar membrane vibrations, as well as the further amplification gained by active outer-hair-cell vibration causes potentials to fire in inner-haircells which form synapses with neurons which eventually send their information, cleaned up a bit, to pathways to the brain.  Transients are still detected by the basilar membrane, but there are stations in the ascending pathways which deal with transient sounds differently than longer, more periodic sounds.  The moral of the story is that there's still a TON of work to be done just on pitch perception - and of course even more on general auditory perception.

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