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Re: mechanical cochlear model

Hello Peter,


Thank you for your protest. The role of the round window is interesting: during a sine-tone of 10 kHz, say, the local wave number of the  travelling surface wave at the base of the human cochlea  is ~0.8 mm^-1; local wavelength = 2pi/k = 8 mm. Width of basilar membrane (BM): w = 0.1 mm; radius of roughly half-circular strong-liquid-motion regions just above and just below BM: r = 0.2 mm. At the round window, there is no liquid motion and no liquid sound pressure. During a sine-tone of lower frequency, 0.5 kHz, say, a (slow) travelling surface wave would require liquid motion and liquid sound pressure in the whole near-base cochlear-channel cross-section, also at the round window. Because of the softness of that window, however, a significant liquid sound pressure on its inside cannot be built up, so at low frequency, there is indeed no significant slow travelling surface wave at the base of the mammalian cochlea, if the round window is not blocked. This can be confirmed, e.g., via Recio and Rhode (2000), "Basilar membrane responses to broad-band stimuli", JASA 108, 2281-2298. 



----Ursprüngliche Nachricht-----------------------
Von: pwj.vanhengel@xxxxxxxxx
Datum: 02.06.2010 12:46
An: <AUDITORY@xxxxxxxxxxxxxxx>
Betreff: Re: mechanical cochlear model

Dear Martin,
interesting results no doubt, but once again I must protest against the conclusions. As I have stated before it is not so easy to abolish or greatly reduce the traveling wave in the cochlea. Any motion of the fluid, in combination with the flexibility of the BM, will cause a traveling wave, even if you severely influence the boundary conditions.
Oversimplification of fluid mechanics in the cochlea has led to erroneous conclusions before...
Just a warning against drawing conclusions too rapidly.
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 .