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Re: MCM: Q.1

Hello once more !

In a well-known ironical style manual, it says "Don't use abbrevs!".
In the subject line above, "MCM" means "Mechanical Cochlear Model",
and "Q.1" presumably means "Question One" (?).

There was a misprint in my posting of March 13 (see below).
In its last paragraph, please read:
"[...] Between 2.2 and 3.8 mm from base, the 20-dB real part of the 
basilar-membrane impedance is negative. [...]".


----Ursprüngliche Nachricht----
Von: andrew.bell@xxxxxxxxxx
Datum: 15.03.2010 04:35
An: <AUDITORY@xxxxxxxxxxxxxxx>
Betreff: Re: MCM: Q.1

Dear Reinhart:

Let me be brief. I'm not wanting to become involved in something like a
beauty contest, where we each pass comment on appealing features of
particular entrants. They are all unique and beautiful in their own way!
What I'm asking is to please just look at Fig. 7 of Lonsbury-Martin et al.
1987 (JASA 81, 1507), with mind open, and WONDER. 

Are you sure it's not resonance?


P.S. Have you read my on-line thesis? It would save a lot of needless
repetition if you have. 

Andrew Bell
Research School of Biology (RSB)
The Australian National University
Canberra, ACT 0200, Australia
T: +61 2 6125 5145
Mob:  0410 403 341

> -----Original Message-----
> From: reinifrosch@xxxxxxxxxx [mailto:reinifrosch@xxxxxxxxxx] 
> Sent: Saturday, 13 March 2010 11:30 PM
> To: andrew.bell@xxxxxxxxxx; AUDITORY@xxxxxxxxxxxxxxx
> Subject: Re: mechanical cochlear model
> Hello Andrew,
> In order to keep the length of my postings reasonable, I 
> shall try to comment on the five points raised in your 
> posting of March 7 one by one, starting with point 1:
> >In addition to Martin's 2 pieces of evidence against the 
> >traveling wave model, we can add:
> >
> >1. The peak of the traveling wave is unrealistically sharp.
> The cochlear travelling wave (TW) at sound-pressure levels 
> >100 dB SPL is about equal to a purely passive wave, since 
> the cochlear amplifier in that case is too weak to make a 
> significant difference. Such a 100-dB wave is shown, e.g., 
> in Fig. 2 of de Boer (2006), "Cochlear Activity in Perspective", 
> in "Auditory Mechanisms"  (Portland Proceedings), World 
> Scientific, New Jersey, pp. > 393-409. 17 kHz, guinea pig. 
> The peak is very wide; amplitude at the base: 22 dB; 
> amplitude at the "passive peak", ~2.8 mm from base: 29 dB; 
> at ~4.1 mm from base, the amplitude has fallen to 19 dB.
> In the same Fig. 2, one sees that, at 20 dB SPL, the TW is 
> very different from that at 100 dB. Between 2.2 and 3.8 mm 
> from base, the 20-dB imaginary part of the basilar-membrane 
> impedance is negative. Mechanical energy is fed into the 
> 20-dB TW, so the amplitude rises in that spatial region. The 
> "active" peak is reached near the apical end of the mentioned 
> negative-impedance-realpart zone. Its -10 dB width is indeed 
> quite small, namely ~1.1 mm.
> Reinhart.
> Reinhart Frosch,
> Dr. phil. nat.,
> r. PSI and ETH Zurich,
> Sommerhaldenstr. 5B,
> CH-5200 Brugg.
> Phone: 0041 56 441 77 72.
> Mobile: 0041 79 754 30 32.
> E-mail: reinifrosch@xxxxxxxxxx .