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Klarinet Archive - Posting 000245.txt from 2001/02

From: Roger Shilcock <roger.shilcock@-----.uk>
Subj: Re: [kl] Organs and combination tones
Date: Thu, 8 Feb 2001 04:32:46 -0500

Dear Tony et al.,
Are you claiming that there is no harmonic component corresponding to a
difference tone which can be detected by any suitable apparatus?
Roger S.

In message <20010207.171924.88@-----.org writes:
> On Wed, 07 Feb 2001 06:50:09 -0500, bhausmann1@-----.com said:
>
> > At 08:20 PM 2/6/2001 -0800, William Wright wrote:
>
> > > So far as I know, the word "hear" is very important because (so far
> > > as I have read) a difference tone is manufactured by flesh in the
> > > human ear, not by interference or summation of sound waves outside
> > > of the ear. (See Arhur Benade, "Horns, Strings, and Harmony, Chapter
> > > IV, pg. 80+ in the Dover paperback edition.)
>
> > > I don't think that the insides of a tuner manufacture a difference
> > > tone, and therefore the tuner won't "hear" a difference tone.....
> > > but I could be wrong.
>
> and later:
>
> > > ....in other words, a difference tone is not the same mechanism ---
> > > is not produced the same way --- as the 'beats' that we use to
> > > verify whether two instruments are in tune with each other. Benade
> > > is quite firm about this, and he discusses this confusion in both of
> > > his books.
>
> > You may be misreading Benade or something, but I don't think things
> > like wall-shaking resultant bass organ notes would work if summation
> > of sound waves was not purely a matter of physics. Nor would standing
> > waves cause any problems. A difference tone does not need to be
> > manufactured; it exists in the air, as surely as two pebbles dropped
> > in a pond will cause interfering waves in the water.
>
> This subject is quite complicated. To the degree I understand it,
> difference tones of frequency (f1 - f2), (as well as other less strong
> combination tones of frequencies (2f1 - f2) and (3f1 - 2f2)) are
> perceived because of the non-linear response of parts of our ear
> (thought to be the cochlea, though not the eardrum itself) to the
> acoustical signal. "They are not present in the original sound
> stimulus." (Roederer, Introduction to the Physics and Psychophysics of
> Music.)
>
> The 'organ' effect mentioned by Grant, which Roederer says is called the
> "periodicity pitch, subjective pitch, residue tone or virtual pitch" is
> even more removed from the physical stimulus, occurring at low
> intensities, and perceivable even if the two tones are fed into separate
> ears (Houtsma and Goldstein, 1972). Thus it "must be the result of
> neural processing at a higher level."
>
> "...repetition rate detection [of the fundamental frequency of the
> combined waveform] has been used in music for many centuries (and
> wrongly attributed to a combination tone effect). For instance, since
> the end of the 16th century, many organs include a stop (the "5 1/3 -
> foot fifth") composed of pipes sounding a fifth higher than the pitch of
> the written note actually played. The purpose is to stimulate or
> reinforce the bass one octave below the written note (ie, to reinforce
> the 16' sound of the organ). Of even older usage is the 10 2/3 - foot
> fifth in the pedals, which, in combination with 16' stops, simulates or
> reinforces the 32' bass (two octaves below the written note)....this
> tone is called the *missing fundamental*.
>
> Tony
> --
> _________ Tony Pay
> |ony:-) 79 Southmoor Rd Tony@-----.uk
> | |ay Oxford OX2 6RE GMN artist: http://www.gmn.com
> tel/fax 01865 553339
>
> .... When everything's coming your way, you're in the wrong lane.
>
>
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............
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In walking naked.
-------------- W. B. Yeats ("A coat")

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