Subject: Re: diaphragm output & phase: HC selectivity ... and the lateral organ of the fish From: Martin Braun <nombraun@xxxxxxxx> Date: Mon, 8 Oct 2007 14:06:24 +0200 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>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 --------------------------------------------------------------------- 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@xxxxxxxx> 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