Strange Noises

Not long ago I put up a post about driving an H-Bridge..
Well..
I hooked it up to a PIC16F84 and was using the PWM command from the PicBasic
Pro compiler The PWM Command is: PWM pin, duty, cycles 1 cycle=5ms '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' For sp0 TO 255 STEP 1 PWM 1, sp, 10 Next sp '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' I was just foolin with it, expecting to see the motor slowly accelerate. That I saw, what I heard was what resembles a music scale..with changing frequency. the frequency was going upward..i assume its the freq of the loop I have no speaker or mic connected I'm not complaining I think its cool. How is this Possible???? Anyone ever have anything like this before?
Thanks, Rick-
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Rick Cassidy wrote:

If you didn't hear this something would be wrong with your ears!
Relax, it's normal. The PWM you're using is well within audible range, and the motors are acting as resonators in response to the frequency of the PWM.
-- Gordon Author: Constructing Robot Bases (Forthcoming) Robot Builder's Sourcebook, Robot Builder's Bonanza
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Gordon McComb wrote:

Imagine what the Gramophone would look like today, if Edison went down this path.
--
Don McKenzie
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