[Cochlea-amp.] mechanical cochlear model

Martin Braun nombraun at telia.com
Thu Mar 18 08:32:10 EST 2010

Continuation of thread of same name from the Auditory List:

Dear Dick and others,

> .......  What you've pointed out is that the
> community knows that the traveling wave involves both localized
> displacements and localized pressure differences across the BM.  We
> agree on that part.
> [.......]
> At least we can all agree with what Robles and Ruggero wrote.

We agree ON what they wrote, not WITH what they wrote! I cited plenty of 
evidence that hearing occurs without membrane displacements.

> .......  None of this suggests
> that the system under test has a threshold inherent in it.

Of course there are inherent thresholds in physics. Just take 0 and 100 
degrees C for water. In biology almost anything has an inherent threshold. 
As to pressure propagation in the cochlear fluids, there is of course a 
threshold between adiabatic and diabatic propagation. If everything in our 
world was diabatic, we surely would not have the term "adiabatic".

> .....  What you
> say is physically impossible is what most of us think is going on:
> amplification of a by-passing basilar membrane traveling wave by
> OHCs.

It is possible for steady state signals, such as tones, but not for 
transients. You have not considered the latency of OHC motility. And please 
recall that in nature almost all sounds are transients. For these sounds a 
traveling wave amplification by OHCs is not possible because of their 


Martin Braun
Neuroscience of Music
S-671 95 Klässbol
email: nombraun at telia.com
web site: http://www.neuroscience-of-music.se/index.htm 

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