"William Sommerwerck" wrote in message
...
I think there are two simple refutations, one theoretical, the other
practical.

Theoretical -- If the output of a driver accurately follows its input
waveform,
how can there be Doppler distortion?

If the driver converted voltage to air pressure, there could be no Doppler
distortion.
However, the driver, even under the best of circumstances, does not do that.
It converts, approximately, to displacement.

Displacement is not equivalent to air pressure.

Practical -- It should be trivial to compute the sidebands produced by
combining
(say) a 60Hz signal and 6000 Hz signal. By looking at the phase of the
sidebands, it should be possible to determine what part of them is IM
distortion
(AM components) and what part is Doppler (FM components).