Subject: Re: A new paradigm?(On pitch and periodicity (was "correction to post")) From: Steve beet <steve.beet@xxxxxxxx> Date: Tue, 1 Nov 2011 02:39:18 -0000 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>I'd just like to add my vote to Dick Lyon's interpretation of the laws of physics: in the cochlea the "free-space" speed of propagation in the perilymph / endolymph would be very high but the transverse dimensions of the structures within the cochlea are small. Consequently there should be only one mode of propagation in the normal audio frequency range - although I'm not sure how well the concept of "modes of propagation" fits with non-uniform partially-elastic structures such as those found in the cochlea. >From the evidence I've seen, the speed of propagation within the cochlea is almost entirely determined by the elasticity and dimensions of the basilar membrane, and the density and viscosity of the fluids in the cochlea. The other structures within the cochlea (notably the tectorial membrane and the active effects of the OHCs) also need to be accounted for if you want a truly accurate model, but I can see no reason to suppose that they are even linear, let alone quantifiable in terms of a simple transmission-line model. Steve Beet -----Original Message----- From: AUDITORY - Research in Auditory Perception [mailto:AUDITORY@xxxxxxxx On Behalf Of Richard F. Lyon Sent: 31 October 2011 21:47 To: AUDITORY@xxxxxxxx Subject: Re: A new paradigm?(On pitch and periodicity (was "correction to post")) In the ear, the stapes doesn't couple much energy into this fast pressure-wave mode. A much slower propagating vibration mode is involved in the cochlear traveling waves that use the compliance of the basilar membrane, as opposed to compression of the fluid, as the displacement-based restoring force that leads to the wave equations.