Subject: Re: mechanical cochlear model From: "reinifrosch@xxxxxxxx" <reinifrosch@xxxxxxxx> Date: Thu, 18 Mar 2010 10:05:21 +0000 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>Hello ! I, too, would be glad if the cochlear-mechanics discussion on the Auditory List could continue. If possible, the postings should be kept short. Today I would like to continue my point-by-point comments on the posting of March 7 by Andrew Bell: >In addition to Martin's 2 pieces of evidence against the traveling wave >model, we can add: >[...] >2. The variation in stiffness is inadequate to tune the cochlea from 20 to >20000 Hz. Three decades of frequency calls for a million times variation in >stiffness (more than between foam rubber and tungsten), and this is in >contrast to measurements of 2 or 3 orders at most. See Naidu & Mountain >1998, Hear Res 124, 124. Bekesy found the value to be about a hundred-fold >(p. 476 of Exp in Hearing). The human BM resonance frequency, f_BMR = (1 / 2pi) * sqrt(S / M) at the base appears to be about 20 kHz. At the apex, however, that resonance frequency may well be considerably greater than 20 Hz. Both in post-mortem and healthy cochleae, the travelling wave does not reach the BM resonance place. At given frequency >1 kHz the passive (active) response peak is basal of the BM resonance place by about 1.0 (0.5) octave distance. In homo, that distance is ~5mm. 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@xxxxxxxx .