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Re: Bite-induced pitch shift?

Dear Bob

Interestingly, I recall there was a discussion on a similar issue by the list a year or two ago.  Hartmann in his book (Signals, sounds and sensation) refers to Corey, V.B. (1950) Change in pitch of a sustained musical note by clenching of the jaws of the observer.  J. Acoust. Soc. Am.;22:640.  As an MSc student I did a modest project a couple of years ago that may be relevant and will be published in Acta Otolaryngol some point this year (should be available online now).  It aimed to replicate a study by Fritze, W. (1995) Acta. Otolaryngol. (Stockh.);115:359-362 who reported upward pitch shifts of as much as 1% at 1000 Hz with changes in static ear canal pressure of +/-4000 daPa.  Fritze (1995) interpreted his findings as indicating an effect of ear canal pressure on place coding.  We figured that 1000 Hz was a slightly ambiguous frequency to try a work out if a pitch shift was due to changes to place or temporal coding.  We essentially measured binaural diplacusis but with changes in static ear canal pressure in one ear.  We found no evidence of a pitch shifts with -300 daPa, 100 daPa less than Fritze, vs. ambient pressure at 4000 Hz and a small but stat signif downward pitch shift (~0.4%) in only 2/7 listeners at 500 Hz.  While we were a little cautious in the interpretation of the data at 500 Hz due to the small effect in only 2 listeners (one of which was me), we certainly found nothing at 4000 Hz.  Hope this helps.

Daniel Rowan
(Rm 1023, Building 19)
Institute of Sound and Vibration Research
University of Southampton
Southampton SO17 1BJ, UK
Phone: +44 (0)23 80592842
Email: dr@isvr.soton.ac.uk

>>> Bob Masta <masta@UMICH.EDU> 06/19/03 08:45pm >>>
Dear List:

In the June 9 issue of  Electronic Design <www.elecdesign.com>
analog electronics guru Bob Pease mentions that when he bites down
hard "on some tough nuts or a popcorn cake, the pitch seems to
dip momentarily by about half a note".

Has anyone heard of a phenomenon like this?  (The effect doesn't
seem to work for me, at least not when biting down on a plastic
toothbrush handle.)  He wonders what can cause this.  If this is
truly a pitch shift and not a resonance envelope (formant) shift
due to distorting the ear canal, could it be deforming the cochlea
such that the stiffness of the basilar membrane is changed?
Seems pretty extreme!  Any ideas?

Robert Masta

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