Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re[2]: Electric Beats?

On Wed, 15 May 1996, Cherie Lehman wrote:

While using a couple of tuning forks to demonstrate beats to some of my
students, I decided to hold the 128 Hz fork near one ear and the 125 Hz
fork near the other ear to check for beats. Pleasantly, I heard 3 beats per
second. I don't think that these could be the result of superposition of
the two compression waves (don't even start with the airhead blonde jokes!)
It is my hypothesis that these beats result from superposition of the
resulting electrical signals which the auditory nerves send to the brain.
Has anyone else observed this phenomenon? It is pretty cool. I would like
to try this with an audiologist's equipment. Just wanted to know what the
phys-l folk thought. It's probably not really new at all -- jut new to me.

Cherie,

The phenomenon you stumbled upon is called "binaural beats" and it is,
indeed, produced within the neural system. One difference between
binaural beats and the ordinary beats produced by superposition of
acoustic waves is that it tends only to occur at low frequencies because
the neural system does not preserve the phase structure of high frequency
waves very well.

This phenomenon and many more are beautifully presented on a CD called
"Auditory Demonstrations" that was prepared at the Institute for
Perception Research at Eindhoven in The Netherlands. I got a copy
through the Acoustical Society of America. I'm sorry that I cannot find
any ordering information in the package.

John
----------------------------------------------------------------
A. John Mallinckrodt email: mallinckrodt@csupomona.edu
Professor of Physics voice: 909-869-4054
Cal Poly Pomona fax: 909-869-5090
Pomona, CA 91768 office: Building 8, Room 223
web: http://www.sci.csupomona.edu/~mallinckrodt/

********************************************************************



The CD was put out by Philips, number 1126-061.

jaskill@mail.millikin.edu