Wasn't v. Helmholtz right? (Eckard Blumschein )

Subject: Wasn't v. Helmholtz right?
From:    Eckard Blumschein  <Eckard.Blumschein(at)E-TECHNIK.UNI-MAGDEBURG.DE>
Date:    Mon, 22 May 2000 13:54:04 +0200

Dear list,

The recent edition of Auditory Perception by Richard M. Warren provides an
excellent review of Mechanics for Stimulation within the Inner Ear.
Unfortunately, the author preferred to leave some conclusions and possibly
some notorious errors to the reader. He wrote correctly: The speed of sound
in the cochlear liquids is very much faster ((than velocity of the
traveling wave)), about 1,600 m/sec (this difference is of significance in
determining whether the traveling wave or the sound pressure is the
stimulus for receptor cell transduction...). He did not, however, mention
the question whether or not the traveling wave is the result of energy
transmission basilar from base to apex inside basilar membrane or it might
rather be an epi-phenomenon, i.e. an attendant symptom of local resonance.
Referring to Lewis, Leverence, and Bialek (1985), and also to de Boer and
Nutall (1996), Dancer, Avan, and Magnan (1997) tried to belittle this
discrepancy by calling the traveling wave a leitmotiv. Recio, Rich,
Narayan, and Ruggero (1998) rejected this point of view. Can anybody point
me to the final outcome of that discussion? Possibly, I am simply not yet
aware of the latest news since I did neither attend a concerning conference
in Japan last year nor the ARO meeting this year.

It is my gut feeling that v. Helmholtz was pretty right with his idea of
local resonance. Otherwise, I was wrong with my speculations on physiology
of the inner ear of some animals, explanation of equivalence of net latency
and 1/CF, problems with understanding of DPOAE, etc. I also realized
evidence for the longitudinal coupling being fairly weak. Local resonance
does neither exclude the appearance of a traveling wave nor the application
of a modified transmission line model (with a nearly common upper potential
along the whole length). I additionally imagine an additional oscillating
motion back and forth in radial direction due to motility of the outer hair
cells. Radial component of velocity was reported ten times larger than the
longitudinal one.

Once again, may I ask for hints to the ultimate elucidation? As Dancer et
al. stated, the two positions should have implications in signal
processing. Suggesting that psychoacoustics may be the touchstone for
theories, I would be curious if it will really be possible to compensate
for the traveling wave delay.

Thank you very much,

Dr. Eckard Blumschein

Inst. of Electronics, Signal Processing, and Telecommunication
Otto von Guericke Univ. Magdeburg, GERMANY