Subject: Re: Bite-induced pitch shift? From: David Mountain <dcm(at)BU.EDU> Date: Fri, 20 Jun 2003 09:13:41 -0400The von Bekesy result (compression of veins causing a 2% reduction in pitch) was most evident for low tones of moderate intensity. The perceptual phenomenon of pitch apprears to depend on both the spectral and temporal properties of the stimulus. Therefore, the pitch shift observed by von Bekesy could be the result in a change in some aspect of temporal processing rather than a change in cochlear mechanics. If the effect is, in fact due to a change in temporal processing, then you would not expect t observe it for frequencies above the auditory nerve phase-locking limit (~2 kHz). If the pitch-shift effect is due to pressure changes altering cochlear mechanics, then perhaps the pitch effect is related to the fluctuating low-frequency hearing loss that is commonly associated with Menieres syndrome. This hearing loss is commonly thought to be due to a static displacement of the basilar membrane caused by increased endolymphatic pressure (endolymphatic hydrops). Small static displacements of the basilar membrane would not cause a significant change in stiffness (see Olson and Mountain, 1991, J Acoust Soc Am. 89:1262-75 as well as our other basilar membrane stiffness papers for examples of stiffness-deflection curves). Static deflections would, however, be expected to alter the operating point of the outer hair cells since the sensitive region of the hair cell transducer characteristic spans only a fraction of a micron (Russell et al., 1986, Hear Res. 22:199-216). -------------------------------------------------------------------- David C. Mountain, Ph.D. Professor of Biomedical Engineering Boston University 44 Cummington St. Boston, MA 02215 Email: dcm(at)bu.edu Website: http://earlab.bu.edu/dcm/ Phone: (617) 353-4343 FAX: (617) 353-6766 Office: ERB 413