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Klarinet Archive - Posting 000534.txt from 2001/02

From: Bill Hausmann <>
Subj: Re: [kl] Difference Tones
Date: Wed, 14 Feb 2001 20:46:54 -0500

At 05:34 PM 2/14/2001 +0000, Tony Pay wrote:
(I wrote)
> > In any case, if a difference tone can be generated that makes physical
> > objects shake, including eardrums, microphone diaphragms, walls, etc.,
> > I just have to believe that it exists in space beyond my own head.
>If a physical object encounters two pure sine waves P and Q, and has a
>non-linear response, then instead of just shaking with frequencies P and
>Q combined additively, it shakes at frequencies P, Q and other
>frequencies combined additively too, including (P-Q), as I said above.
>THIS is the case for the middle ear.
>But if the physical object *doesn't* have a nonlinear response, then it
>*doesn't* shake with frequency (P-Q).
>THIS is the case for the eardrum.
>So what sense does it have to say that the frequency (P-Q) is *present*?
>In one case it's generated, in the other not, that's all.
>As well say that you're always saying 'ouch!', just because you *do* say
>'ouch!' when you bang your thumb with a hammer.

I'm not sure if I follow completely, but if the combination of two pipes
causes objects to vibrate at a frequency P-Q (among others), the
transmission of that vibration must happen in one of two ways: direct
conduction or air vibration, that is, sound waves. Suppose you ignore the
possibility of sound waves conducting that vibration TO the object. What
happens when the object(s) itself (eg., the walls) vibrating at that
frequency due to direct conduction excites the air to vibrate at that

Bill Hausmann
451 Old Orchard Drive
Essexville, MI 48732 ICQ UIN 4862265

If you have to mic a saxophone, the rest of the band is TOO LOUD!

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