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Klarinet Archive - Posting 000280.txt from 2001/02

From: Tony@-----.uk (Tony Pay)
Subj: Re: [kl] Combination tones......
Date: Thu, 8 Feb 2001 19:01:24 -0500

On Thu, 08 Feb 2001 18:43:28 -0500, bhausmann1@-----.com said:

> I think what happens is that when these beats occur at a frequency
> within hearing range (i.e., greater than 20 Hz) that frequency is
> ITSELF heard (or, if lower, FELT) as a separate tone, rather than
> being identified as individual beats.

Tempting of course to think that, and I thought it for many years -- but
apparently not so.

One of the things about the 'approach' to the 'organ' effect (eg,
combination tones at an 'octave approximation', or a 'fifth
approximation' rather than a unison approximation) that I didn't mention
previously -- though Roederer does -- is that the summed waveform
exhibits a periodic change of *form*, but not of *amplitude*, so there
is no 'amplitude beat', but simply what you might call a 'form' beat,
that you can see on the oscilloscope.

In this approach to precision, if the slightly tones that constitute the
approximation are presented to separate ears, the perceptual beating
experience remains, but is a curious one -- the sound, he says, seems to
'rotate' periodically. And at octave or fifth precision, we still
perceive the difference tone.

As Roederer points out, all this must be due to later neural processing
of the signal.

Tony
--
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|ony:-) 79 Southmoor Rd Tony@-----.uk
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