Re: A new paradigm?(On pitch and periodicity (was "correction to post"))

[Steve beet <steve.beet@xxxxxxxx>]

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@xxxxxxxxxxxxxxx] On Behalf Of Richard F. Lyon
Sent: 31 October 2011 21:47
To: AUDITORY@xxxxxxxxxxxxxxx
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.