"Jeff Liebermann" wrote in message
...
An audible beat tone is produced by the constructive and destructive
interference between two sound waves in air. Look at a pictorial
representation (in the time domain) of the sum of sine waves,of similar
amplitudes, one at, say, 1000 Hz and the other at 1005, and you'll
see it.

Bob M.

I beg to differ. There's no mixing happening in the air.

Nor did I say there was. The phenomenon of interference
between two compression waves in a given medium is not
an example of "mixing."

of air is very linear (Boyles Law or PV=constant). If there were
mixing, you would be able to hear the beat note when one generates two
ultrasonic tones. I belch 25KHz and 26KHz from two transducers, by
our logic, air mixing would create a 1KHz beat note. It doesn't and
you hear nothing.

That was exactly my point. Please read ALL responses I've
made re this topic.

What seems to be the problem here is the model of the human ear is not
what one would assume. It is NOT a broadband detector. The cochlea
cilia (hairs) resonate at individual frequencies. Each one resonantes
at only one frequency (and possibly some sub-harmonics). Therefore,
the human ear model is a collection of narrow band filters and
detectors. Unless the two frequencies involved both cause a single
cilia to simultaneously vibrate at both frequencies, there isn't going
to be any mixing. Each detector can be individually quite non-linear,
but as long as it vibrates at only one frequency, there isn't going to
be any mixing.

This is also a point I noted earlier in this thread.

Bob M.