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Re: diaphragm output & phase: HC selectivity ... and the lateral organ of the fish

Dear Steve, Kevin, A.J., and others,

Yes, microphones can teach us quite a bit about hearing. Microphones detect
pressure gradients of propagating sound waves.

The molecules of the medium, air or water, accelerate the microphone
membrane, the so-called diaphragm. Thus the membrane is catapulted, not
carried, by air or water molecules. Therefore the resulting membrane
displacement can be larger than the molecule displacements by several orders
of magnitude. An easy analogue is the shotgun, where the bullet is
accelerated over a distance of < 1 m but then can fly over several 1000 m.

The same thing in hearing. While a basilar membrane (BM) acceleration over a
distance of 1 pm can NOT catapult hair bundles into displacements of
hundreds of pm (because BM and hair cells are solidly coupled), the sound
waves entering the cochlea via the stapes can easily do so.

This is not only the evident method of transduction in vertebrates without
BMs or traveling waves, it also occurs in hundreds of thousands of insect
species. Here it could be observed that air molecules catapult the hearing
antennae into nanometer excursions.

What the hearing antennae of insects do in the air, is what the cilia of
vertebrate hair cells do in the endolymph. Some insects even produce
otoacoustic emissions with their antennae. Apparently for exactly the same
reason as vertebrates do, including humans.

Some years ago, cochlear researchers became aware of these amazing parallels
between insect and vertebrate hearing. And since 2002 they have been
inviting prominent insect researchers to their meetings.

Martin

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Martin Braun
Neuroscience of Music
S-671 95 Klässbol
Sweden
web site: http://w1.570.telia.com/~u57011259/index.htm




----- Original Message ----- From: "Steve Beet" <steve.beet@xxxxxxxx>
To: <AUDITORY@xxxxxxxxxxxxxxx>
Sent: Sunday, October 07, 2007 11:13 PM
Subject: Re: diaphragm output & phase: HC selectivity ... and the lateral
organ of the fish


Ok, I really will keep it short this time!

I may be guilty of over-simplification, but to find more definitive
information about different types of microphone, click, read, and inwardly
digest everything at this URL:

http://en.wikipedia.org/wiki/Microphone

Steve Beet