"Porky" writes:

"Randy Yates" wrote in message
...
Bob Cain writes:

ruffrecords wrote:

To produce FM there needs to be a non-linearity. If you detect FM
there is a good chance a non-linearity exists. But it is not due to
the doppler effect.

Exactly,

Not. Get a clue, people. Doppler is a *PHYSICAL PHENOMENOM* that
WILL happen whether or not you decide it can WHENEVER a sound wave
source and observer are moving relative to each other. Period. This
isn't open for debate.

This whole argument is based on the wrong assumption that the high
frequency source is "riding on" the low frequency source like a whistle on a
train. It is NOT!

Oh, but it is. That is precisely what is happening.

Both sounds are being produced simultaneously by the
complex electrical waveform driving the speaker cone which moves in
accordance.

True, and how does that refute that there is no Doppler? Before it
ever gets to a speaker, such an electrical signal will have the
characteristic of the high frequency wave "riding" on top of
the low frequency wave. You will see it on a scope. Input that to
a speaker and you will see precisely the same thing if you observed
a plot of speaker cone displacement versus time.

Assuming that the speaker is being driven within its linear
limits, the cone's motion accurately follows the driving signal,

True.

and it is a
linear system.

FALSE! Well, at least if you define "it" to be the entire composite system
from the speaker's electrical input to the acoustic receiver's input. In
that case, it ain't linear. That's the whole point. The physics of what
happens between the speaker cone and the acoustic observer are such that
Doppler will take effect. Now how *much* Dopper is another question, but
the effect will be there for sure, just as two masses will experience an attraction
based on the inverse square law (m1*m2/r^2).

Forget the train/whistle anology, it is not an accurate representation for
what goes on with a speaker, period!

Proof by assertion?
--
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