cw@vaxwaller.UUCP (Carl Weidling) (08/29/84)
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
dave@rocksvax.UUCP (09/05/84)
You would only hear the 1Khz note from the 30 and 31Khz signal if the
signals are applied to a non-linear (mechanical) junction. Then you will
create the sum and difference intermod products that would produce a
1 Khz tone. Chances are they created the 1Khz in the radiator that
produced the tones, and if you use a microphone to record what the
person heard, indeed you would pick up a 1Khz tone. Now on the other
hand if the non-linear mixing joint was in the ear, you probably
would not pick this signal up in a recording.
Dave
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