Cochlea -- quality of filtering

DONALD A KAISER dakaiser at WELCHLINK.WELCH.JHU.EDU
Wed Sep 20 14:51:53 EST 1995



Don A. Kaiser
Cell Biology
117 WBSB
Johns Hopkins Univ.
Sch. of Medicine
725 No. Wolfe St.
Baltimore MD 21205
410-955-5672 TEL
410-955-4129 FAX


On 20 Sep 1995, Eric Smith wrote:

> 
> How well does the cochlea divide sound into its frequency components?
> For example, a 100 dB, 6000 Hz, pure tone, stimulates the hair cells
> for 6000 Hz.  But does it avoid stimulating any 5000 Hz hair cells at
> all, or does it stimulate those with a small fraction of the energy it
> applies to the 6000 Hz hair cells?  Can anyone supply any kind of
> formula for estimating how much stimulation there will be at different
> frequencies when a single pure tone is applied?
> 
		My understanding is that the hair cells themselves are not 
very specific or "selective" to particular frequencies.  That is, when a 
particular frequency is sounded, a whole range of hair cells whose natural 
harmonic frequencies are above and below the frequency of the sound, are 
excited.  My recollection is that the band is very broad and fairly well 
centered around the hair cells whose natural frequency matches that of 
the sound.  However, the actual perception of a "frequency" occurs from 
some filtering process in the nervous system.  This, I'm afraid, is very 
poorly understood?  I am sure that a more precise answer to your question 
is known but I can only surmise that the 5000Hz cells will certainly be 
stimulated by the 6000Hz pure tone.  



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