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Klarinet Archive - Posting 000314.txt from 2001/02

From: Tony@-----.uk (Tony Pay)
Subj: Re: [kl] Combination tones......
Date: Fri, 9 Feb 2001 14:43:21 -0500

On Thu, 8 Feb 2001 17:28:12 -0700, gdgreen@-----.com said:

George Kidder said:

> > You are saying that if you start with two tones (say 1000 and 1001
> > Hz) you will hear a pulsation (a variation in amplitude) at a rate
> > of 1 Hz, and that this 1Hz is a new tone? That is, it is really
> > physically there?

[snip]

> Yes, exactly. The difference tones arise from the cancelation and
> reinforcement of two non-unison frequencies[.]

This is a confusion of levels. Yes, the variation in amplitude is
visible, as you say, on an oscilloscope and in the math. But it isn't
*physically* there, because it doesn't 'waggle' anything real. The
pressure wave itself is already doing that.

A 'waggle' in a concept like amplitude isn't perceivable by an eardrum
-- it's already busy being waggled by something else: namely the forces
involved.

You can see though, as I said in another thread, why the idea is
attractive. In fact, it was put forward by Young in 1784, but
contradicted by Helmholtz in 1877, who explained the picture outlined by
George Kidder here.

This true explanation of why we perceive a difference tone is actually
much more suggestive, even though a bit difficult to approach.

Tony
--
_________ Tony Pay
|ony:-) 79 Southmoor Rd Tony@-----.uk
| |ay Oxford OX2 6RE GMN artist: http://www.gmn.com
tel/fax 01865 553339

... So... Nice weather we've been having...

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