Re: Bite-induced pitch shift?

[Daniel Rowan <dr@xxxxxxxxxxxxxxxx>]

At the risk of getting a little out of my depth it strikes me that if the pitch of a tone is suggested to change with jaw clenching/ear canal pressure because of an effect on outer ear physiology, e.g. reduction in TM compliance, this requires that the frequency of the tone be changed which implies something highly non-linear and it was my information that this would not occur in the middle ear.  Even if a load of harmonics are generated because of frequency distortion, this would not change the pitch of the tone.  We assumed that if the effect of ear canal pressure on pure tone pitch perception was 'real', and not simply pitch-intensity effect or wandering of binaural diplacusis over time, that the origin was at least intracochlear, although that doesn't narrow it down much!

As the discussion appears also to be drifting towards effects of posture, it may be relevant to note the van den Brink has reported an effect of posture on pitch:

van den Brink, G. (1980) Cochlear mechanics as the possible cause of binaural diplacusis?  In G. van den Brink & F.A. Bilsen (Eds.), Psychophysical, physiological and behavioural studies in hearing (pp.64-67).  Proceedings of the 5th international symposium on hearing.  Delft: Delft University Press.  

There are also a number of articles suggesting that SOAEs and external tones interact to influence pitch perception.  It seems to me that if one can reliably influence the frequency of the SOAE using a manipulation that, at least in some frequency regions, doesn't appear to influence pitch directly i.e. in the absence of SOAE, such as with ear canal pressure, one has a direct way to investiagte SOAE-tone interactions on pitch.

Daniel

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
http://www.isvr.soton.ac.uk/

>>> Eric Clarke <e.f.clarke@SHEFFIELD.AC.UK> 06/20/03 05:36pm >>>
I'm surprised at the puzzlement over this effect.

I've noticed it for years - but it's distinctly a small INCREASE in apparent
pitch - perhaps 1/8 semitone (I've never tried to measure it). And I can get
it by just clenching my teeth hard while listening to a pitch. I just
confirmed it now with a piano note. I've no idea of the explanation - but
I've always assumed that it was a slight stretching (tightening) of the
tympanic membrane caused by the jaw muscle tension, or something like that -
or I suppose the muscles attached to the ossicles. But I'd be astonished if
it was a pitch effect caused by an intensity change. That seems more
'roundabout' than is justified. (Though I admit that my own hunch is quite
possibly completely wrong).


Eric Clarke


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