Bekesy model

[Douglas Creelman <creelman@xxxxxxxxxxxxxxxxx>]

Dear Christian,
This is in reply to your search for a demonstration cochlear model.
Another way to go is a purely mechanical model. In the 1950s I was 
fortunate to share a laboratory room at Harvard's Psychoacoustic 
Laboratory with Bekesy. He constructed a cochlear model by hanging 
closely spaced steel(?) balls from string along a 4-metre long beam. 
String lengths changed from "base" to "apex." When the beam was rotated, 
you had a Helmholtz cochlea; one ball would resonate to the frequency of 
rotation.
When adjacent vertical strings were connected with short horizontal 
strings, with a smaller weights in the middle of each connector, you had 
a continuous membrane model, and a Bekesy cochlea. The system could be 
driven by swing the basil (oval window) end pendulum, or by rotating the 
beam. In either case a traveling wave was generated, which settled to 
maximum action at the appropriate point, with a clear effect of critical 
band as adjacent pendulums acted with less amplitude.
Bekesy made a movie of the model, which was quite lovely, with the 
sinuous traveling wave viewed from the end of the model and growing 
activity at one location. I believe the movie was shown at an Acoustical 
Society meeting around 1955 or 56.
I wonder if a copy of that movie exists; it would be great to have it 
available for the kind of demonstration you contemplate.
All the best,
Doug Creelman

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