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In Reply to: Very good questions, only 9 is a bit stupid... posted by Frank on December 29, 2003 at 15:37:10:
This is not the best forum for this since we lack sufficient space and graphics tools. (See the link for one presentation.) In addition, it is hard to know what the background of each read is. Nonetheless, here are some comments on your comments.1)about how many "hair" per freq. group?
At least two.
[Depends on your definition of group. There is 1 inner and 3 outer hair cells (not hairs) per cross-section but their longitudinal spacing along the basilar membrane is fairly continuous so any grouping is not apparent.]2)do these regenerate?
No, but can't be shure as some people have hair growing out of their ear.
[So far as we know but there is evidence in some animals of stimulated regeneration.]3)why do the high freq. "hair" go out 1st with time?
The one's in that range are thin and brittle and susceptable to wear and tare.
[There are several mechanisms but the 'hairs,' themselves, are of similar construction which should make them all equally susceptible. The HF ones are shorter and, thus, stiffer for the higher frequencies such that they can respond better to HF. One possible mechanism is environmental and related to the noises to which one is exposed. Another has to do with the placement of the HF cells at the base of the cochlea where the energy enters.](It seems we live longer these days than nature intended.)
[Mebbe. Or mebbe we live under conditions that make it seem so.]4)whats their bandpass characteristics?
Wide band. Neighboring frequencies also cause the hair to resonate. I don't know if you have ever seen the mechanical indicators used to indicate a generators output frequency, they work in a similar fashion. This bell shaped response curve is also observed in certain measurements to determine noise and distortion
[Resonance properties of the hairs and the local mechanical properties of the basilar membrane are both contributors.]
5)are they located in group or evenly distributed on the surface of their location?
I don't know, my quess it's not evenly distributed since the sensitivity for various frequency regions differs. More hairs for the midrange so it seems.
[Frequency detection preferences are distributed such that 20-5KHz occupies the distal portion of the basilar membrane with 5K-20KHz occupying the proxmimal 1/3. Each octave occupies a similar size interval.]
(The distribution on the eyes retina isn't even either.)
[Yup but the pattern's quite different.]6)how do they couple to the neurons?
Pull out a noisehair and you'll know how.
[Explains nothing. The 'hairs' are extensions, called kinocilia and stereocilia, of the sensory cells. Deflecting them, as when there is relative movement between the basilar and tectorial membranes, opens channels and causes a change in the voltage across the cells membrane. This change modulates the release of a chemical transmitter which is detected by the neurons that transmit the signals to the brain.]7)do they exhibit extended decay/ringing to waves?
Yes, but I'll doubt it matters. Inner ear is filled with fluid to transmit the signal more efficient. It also act as dampening.
[True and there are also active tuning/damping mechanisms, some involving those outer hair cells.]8)how does the inner ear canal resonate and how is that reflected in the "hair" group population/coupling?
Sound is transmitted through the fluid. The complete structure is more or less like a transmissionline curled up. (Seen that shape somewhere in a clossy speaker folder)
[Cute. Take a look at the original B+W Nautilis for a good model of the shape of the cochlea. Or look at any decent Neuroscience text or look up the work of von Bekesy or Hudspeth.]9) why dont i know nothing about this and yet spend 1000s on gear and music?
Different hardwiring in the brain perhaps?
[I appreciate my wife without fundamental understanding......]Kal
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Follow Ups
- Re: Very good questions, only 9 is a bit stupid... - Kal Rubinson 12/29/0318:27:41 12/29/03 (5)
- im surprised a concoction like this works at all... - NonA 10:10:33 12/30/03 (2)
- And the bee flies... - Kal Rubinson 15:51:39 12/30/03 (1)
- Thanks, i started probing the ref's in the link you gave ... - NonA 05:24:45 12/31/03 (0)
- Kal: This is starting to feel like old times... :) [NT] - LarryB 08:42:24 12/30/03 (0)
- Everyday you learn something new. - Frank. 00:30:33 12/30/03 (0)
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