Klarinet Archive - Posting 000442.txt from 2001/02

From: Tony@-----.uk (Tony Pay)
Subj: Re: [kl] Difference Tones
Date: Mon, 12 Feb 2001 09:53:04 -0500

On Mon, 12 Feb 2001 00:29:52 -0500, kkrive@-----.com said:

> Dear Difference Tone Combatants,
>
> Not being versed in the more esoteric regions of the physics of sound,
> I can relate only empirical evidence that a pitch, in addition to two
> different pitches being sounded, may be heard if it is within the
> range of hearing of a listener. It seems to me that if it is heard, it
> must "exist" to the extent that any other pitch "exists." Exactly
> where it "exists" is, of course, the source of confusion and
> disbelief, as well as the subject of scientifically supported
> assertion.

[snip of intelligent remarks about use of difference tone perception in
teaching]

You write:

> It seems to me that if it is heard, it must "exist" to the extent that
> any other pitch "exists."

No, it exists to the extent of being heard, like other pitches; but not
to the extent of being a real vibration in the air, like other pitches,
independently of your hearing it.

As Mark Charette pointed out with an example, the same thing happens in
vision, too. And when your visual systems are disturbed, so that you're
dizzy, you see the room going round and round. You wouldn't want to
claim that this rotation exists to the extent that any other perceivable
quality of the room exists.

I know Bill Hausmann is worried about the organ stop that makes the
walls of his church 'shake'. But whatever the explanation of this is,
it can't be due to the production of a lower frequency *perception* by
the addition of a higher pipe (as was sometimes done in early pipe
organs).

Perhaps his organ uses a more modern technique. An electronic device
called a ring modulator produces real sum and difference tones from two
inputs, but I don't know whether that technique is ever used in organs.

In order to have any idea at all, I want to know more about the
'shaking'. Is it a space resonance on certain notes, or noticeable at
all pitches? How do you detect it, Bill, with your hand?

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

... Data, I thought you were dead! No, sir, I rebooted

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