Ben Bradley wrote:


Bob, I expect you believe the shaker table description, so you
shouldn't have to actually do it.

Ben, you may not have seen it in my posts for the last week
or so but I am no longer disputing that a Doppler distortion
phenomeon exists and that your experiment would show it even
with ideal speakers. It's patently obvious from the thought
experiment of a speaker on a long swing emitting a tone.
Where I remain in divergence from the mainstream is the
cause of it. I do not believe that if you were to do the
two tone experiment with a clean piston in a tube such that
the boundry conditions enforce the creation of a plane wave,
that you would see any Doppler distortion. Mainstream
thinking says you would. The reason it doesn't is that the
coupling of speaker to a distant receiver is a constant,
frequency independant function in that case. I say that
mixing does not occur at the piston/air interface but
further out in the radiated field instead.

What I am disputing at this point is the mechanism. It does
not occur because of little fast waves riding on big slow
ones in the cone but rather under circumstances where the
coupling from speaker to detector is frequency dependant. A
speaker in a box has a very frequency dependant coupling
to the far field and will evidence Doppler distortion.

An ESL in a push-pull configuration is a very low distortion
emitter and has the advantage that the diapragm motion can
be very accurately measured by incuding the capacitance
between the diaphragm an one of the push-pull plates in a
tuned RF modulator. An FM detector on that RF signal will
quite accurately tell what the diaphragm is actually doing
so as to provide a reference signal for any experiment.

I predict that such a system will show no Doppler distortion
in a tube if one can be constructed. The requisite
terminations at the ends is probably too difficult, however.
If it is too difficult, the ESL can be used free standing
for a different experiment. If the principle of my theory
of what causes Doppler distortion is correct, the amount of
it will increase relative to the signal as you distance
yourself from the speaker if the low frequency used in the
experiment is low enough that its coupling to the receiver
decreases much more rapidly with distance than the high
frequency one. The principle I am trying to refute would
make the amount of distortion relative to the signal
independant of the receiver position in space.


I can suggest some sauce for your hat, it's Mezzetta's Habanero
sauce with the appropriate words "Twist and Shout" on the label. It's
definitely up there on the heat scale, but not as concentrated as the
"Hell Hot" sauce which seems to have a lot of radioactive byproducts.
Mezzetta's has a touch of sweet (?) taste along with the hot flavor,
while others of just have the hot flavor piled on top of the hot
flavor. Putting a teaspoon or two on the edge of your plate and adding
a small bit to each bite can add that extra flavor to even the
toughest dishes.

I will definitely save that recipe should either solid
experiment or theory refute the principle on which I think
an accurate theory can be based. :-)

Without a full development of either, I've shown how the
predictions of mine and the popular one will differ with a
fairly easy experiment to set up and do (as experiments go.)
Wish I could do it myself but I have neither the resources
nor the available time.

I still haven't seen any attempt at all to refute the
argument which says it can't exist with a piston in a tube
because of the principle of reciprocity. Several have
hollered that reciprocity doesn't apply to pistons driving
air but without a single detailed reason why not without
appeal to sound pressures that yield a signifigantly
non-linear relationship between pressure and velocity.


Bob
--

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

A. Einstein