Arny Krueger wrote:

"Porky" wrote in message



I think you're right, Bob, that certainly seems logical to me. If it
is Doppler distortion, the tone should be vary in a continuous warble
from -50Hz to +50Hz because the woofer's velocity is continuously
changing.


The FFT plots are snapshots of a kind, but they are also time-exposures. 1
million points at 96 KHz is about 11 seconds worth of data. It is all
averaged together in those pictures.

If one uses a low enough modulating frequency, and a small enough sample
set, snapshots with a faster effective exposure times result.

One can then actually can see the carrier warbling. It will show up at
different frequencies at different times in a sucession of snapshots.

However, with a long exposure you see the results averaging of about 550
cycles of the 50 Hz tone.

That's some excellent hand waving, Arny. But it doesn't
explain where all those other frequencies disappear to.
There's nothing in an FFT of one cycle of the low frequency
that would average them away. That's nonsense.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein