Re: Bite-induced pitch shift?

[Martin Braun <nombraun@xxxxxxxxx>]

The most simple explanation would be that Bob heard a level effect instead
of a pitch effect. It is notorious that both are confused easily.

Possibly he triggered his middle ear muscles. The relevant paper on the
issue is this one:

Burns EM, Harrison WA, Bulen JC, Keefe DH (1993) Voluntary contraction of
middle ear muscles: effects on input impedance, energy reflectance and
spontaneous otoacoustic emissions. Hear Res 67, 117-127.

Abstract
Two types of measurements were performed on a subject able to voluntarily
contract her middle ear muscles (MEM). First, wideband measurements (0-11
kHz) of middle ear input impedance and energy reflectance were obtained when
the subject was relaxed and when she contracted her MEM. The changes in
impedance observed with voluntary MEM contraction were similar to those
reported in the literature for acoustically-elicited MEM contractions. The
energy reflectance increased for frequencies below about 4 kHz. Second, the
effects of voluntary MEM contraction on the frequencies and levels of
spontaneous otoacoustic emissions (SOAEs) were measured and compared to
effects evoked by contralateral acoustic stimulation. Effects on SOAEs
appear to be a more sensitive indicator of MEM activity than changes in
impedance, and the effects due to voluntary MEM contraction were
qualitatively similar to those evoked by contralateral acoustic stimulation.
These results suggest that in subjects with normally-functioning middle
ears, only some effects on otoacoustic emissions caused by contralateral
stimuli whose levels are below the contralateral acoustic reflex threshold
can be unequivocally attributed to the action of cochlear efferents. The
temporal aspects of SOAE frequency shifts caused by voluntary contraction of
MEM show that voluntary contraction fatigues rapidly over a time period of
tens of seconds.

Martin

-------------------------------------------
Martin Braun
Neuroscience of Music
S-671 95 Klassbol
Sweden
web site: http://w1.570.telia.com/~u57011259/index.htm


----- Original Message -----
From: "Bob Masta" <masta@UMICH.EDU>
To: <AUDITORY@LISTS.MCGILL.CA>
Sent: Thursday, June 19, 2003 9:45 PM
Subject: Bite-induced pitch shift?


> 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?