Re: Laws of physics and old history; BM stiffness.

```Dear list,

just a word of caution: the stiffness term used in cochlea models
(transmission line models) should not be confused with the stiffness of
the BM fibers. The stiffness term in these models represents an overall
stiffness of the cochlear partition, and thus includes more than the
stiffness of the BM fibers. Relating the two directly, or even asssuming
they are the same, may lead to misinterpretation.

I do, however support the remark by dr Frosch that depending on the way
in which the beams are fixed at their ends, the stiffness of the BM may
decrease by several orders of magnitude from base to apex.

All the best,
Peter van Hengel

Op 11-11-2011 12:35, reinifrosch@xxxxxxxxxx schreef:
> Hello!
>
> The following is a reaction to an earlier post of this thread:
>
> As already posted some years ago, it appears possible to me that the
> stiffness S [Newtons per m^3] of the mammalian cochlear basilar membrane
> (BM) decreases by several orders of magnitude from base to apex. If the
> elements of the BM are treated as elastic beams, then the following
> formula for S is obtained:
>
> S = n * Y * (delta-z)^3 / w^4,
>
> where delta-z is the beam thickness, w is the beam length (equal to the
> BM width), and Y is Young's modulus of the beam material (elasticity
> modulus, Newtons per m^2); the integer n depends on the way in which the
> beams are fixed, at their ends, to the walls of the cochlear channel. If
> the beams are clamped, then n = 60, if not, then n = 10.
>
> Fig. 11-73 of von Bekesy's book "Experiments in Hearing" (1960) yields a
> human BM stiffness decrease of only two orders of magnitude from base to
> apex. Has that experiment been re-done?
>
>
> Reinhart Frosch,
> Dr. phil. nat.,
> CH-5200 Brugg.
> reinifrosch@xxxxxxxxxx .
>
>     ----UrsprÃngliche Nachricht----
>     Von: rsran@xxxxxxxxxxx
>     Datum: 09.11.2011 20:17
>     An: <AUDITORY@xxxxxxxxxxxxxxx>
>     Betreff: Re: Laws of physics and old history (A new paradigm?(On
>     pitch and periodicity (was &quot;correction to post&quot;)))
>

```