source file: m1461.txt Date: Mon, 29 Jun 1998 10:23:21 -0400 (EDT) Subject: Re: Basilar membrane From: "Ewan A. Macpherson" > Date: Sun, 28 Jun 1998 01:44:54 -0700 > From: Carl Lumma > My question is: Does anybody know how the basilar membrane works? I > thought that a given spot on it was sensitive to a particular > frequency, and that these spots were arranged in order of decending > frequency along its length. Now what stumps me is how a given > frequency only vibrates an isolated part of the membrane. You're right, a point on the BM can't respond to only a single frequency. Instead each point acts like a bandpass filter. Excitation causes a travelling wave to move down the BM, and different frequency components of the wave peak at different places as it progresses. The portion of the BM nearest the middle ear is stiffest and responds best to high frequencies, and the membrane becomes increasingly floppy along its length, lowering the "best frequency" of the bandpass filters. For some nice animations see: http://www.neurophys.wisc.edu/animations/ or download the whole "Auditory tour" (20MB): http://www.neurophys.wisc.edu/ftp/pub/aud-tour/ -- Ewan Macpherson Central Systems Laboratory Kresge Hearing Research Institute http://www-personal.umich.edu/~emacpher ------------------------------ End of TUNING Digest 1461 *************************