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From: cw@vaxwaller.UUCP (Carl Weidling)
Newsgroups: net.audio
Subject: High Frequency sounds being audible
Message-ID: <160@vaxwaller.UUCP>
Date: Wed, 29-Aug-84 16:17:56 EDT
Article-I.D.: vaxwaller.160
Posted: Wed Aug 29 16:17:56 1984
Date-Received: Tue, 4-Sep-84 07:36:04 EDT
Organization: Varian, Walnut Creek, CA
Lines: 29


	At various times discussions have occurred about whether or
not certain "golden eared" people can hear above 20kHz.  I recently
read a book, 'Science and Music', that was written in the late 30's
by Sir James Jeans which I found both readable and informative.  In
one chapter he talks about how assymetrical properties of the human
ear cause it to generate sounds not being produced outside the body,
hence not sounds that a microphone would pick up, unless I've mis-
understood the section.  One of these sounds is a difference frequency
between two frequencies that are being produced.  From what I understand
I think this means that if two sound sources were producing sounds at
frequencies of 30 kHz and 31 kHz, and the recording/playback system
cut off at 20kHz, you would hear nothing in the playback, but if you
were really there, you would hear a 1 kHz tone.  The same applies if
the frequencies were 130 kHz and 131 kHz.  Even if my proposal is
correct I doubt that it has any musical significance, but I wonder
if it explains why some people hear some difference between systems
when one system is faithful up to superaudible frequencies.
	Anyone care to comment?
	BTW I found 'Science & Music' in a bookstore in paperback,
put out by Dover Publications, Inc., New York.  It doesn't require
knowlege of mathematics beyond fractions and covers the physics of
string and wind instruments, acoustics, and origins of musical scales.
I particularly like the section on scales with its exposition
on the origin of the circle of fifths, and the differences between
just intonation, the mean tone system, and equal temperament.
				Regards,
				Carl Weidling