William Sommerwerck wrote:

I don't think you can do it. Your prior explanation about using the standard
Doppler Effect formula does not apply because it assumes a constant linear
motion and a single frequency. It does not handle oscillating motion or
multiple frequencies.


It does if you replace the constant velocity with the varying velocity of the
cone, which is a trivial derivation and insertion. Duh!

That's simply wrong.


As for multiple frequencies...

There is a basic law of mathematics called the principle of superposition. It
predicts that it doesn't matter how you move the speaker cone -- bodily, by
moving the driver as a whole, or electrically, by applying a low-frequency
signal. The results will be identical.

That's not what the principle of superposition is about at
all. In systems where the principle applies, it means that
you can add together the results of the system's effect on
two separate signals going through a system or you can
measure the result of adding the two signals first and you
will get the same thing. It only applies to linear systems,
and certainly not to the one we've been considering (other
than the piston in a tube.)


"You people" are amazing. You want an instant answer to a question without
having to reason it through. And if you don't like the answer -- regardless of
how well-reasoned it is -- you reject it.

With all due respect, I'm afraid you are out of your depth
in your reasoning on this problem.


Bob
--

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

A. Einstein

William Sommerwerck wrote:


SPARE ME YOUR STUPID COMPLAINING. DO THE EFFING MATH.


Plonk.


Bob
--

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

A. Einstein

It does if you replace the constant velocity with the varying velocity of
the
cone, which is a trivial derivation and insertion. Duh!

Be careful... If you setup the problem wrong, you'll come to the wrong
conclusion. One radiator is emitting two frequencies coupled to the same air
mass isn't the same as one radiator moving about inside an air mass, which
is what the Doppler formula is about. The vs term in the Doppler formula
isn't radiating energy or coupled to the air mass.

There is a basic law of mathematics called the principle of superposition.
It
predicts that it doesn't matter how you move the speaker cone -- bodily,
by
moving the driver as a whole, or electrically, by applying a low-frequency
signal. The results will be identical.

If the low frequency is coupled to the air mass in such a way that it is
radiating sound as effiently as it is at the higher frequencies, the energy
transfer is different. If the radiator is just "flopping around" at the
lower frequency without creating sound waves, the higher frequency will be
doppler-shifted.

"You people" are amazing. You want an instant answer to a question without
having to reason it through. And if you don't like the answer --
regardless of
how well-reasoned it is -- you reject it.

Regardless of how well reasoned? I think we have two problems. First, it may
not be as well-reasoned as you think. You migh have set up the problem
incorrectly, and that's being rejected.

Now, I make no claims of expertise or training, so don't ridicule me for
asking what if I have a lower frequency of 50 and a higher frequency of
51.
How can I use the standard formula? What's Fs?

This is a valid point. But hold off for a while. We still haven't resolved
the
basic question.

Bingo! I don't think anyone on this thread (at least in rec.audio.tech) has
yet presented the fundamental physics relating to this problem so no one
really knows that they're talking about (including myself -- no offense).

"Ken Plotkin" wrote in message
...
On Sat, 21 Aug 2004 04:26:53 -0700, "Ron Hubbard"
wrote:

You know, you seem to say that to a lot of people as if you've never heard
the expression, "Put up or shut up."
Why don't you try that sometime; I'm sure it'll be a novel experience for
you.

Seems to me that Gary has "put up" plenty of times. Even on this
topic, he's taken the time to perform an experiment and report the
results. I think his posts have come within a hair of handing
everyone the answer on a silver platter.

The OP experiment (a high-frequency radiator mounted on a low-frequency,
non-radiating platform) are not the same conditions as a loudspeaker (a
high-frequency radiator mounted on a low-frequency, *radiating* platform).
You can't separate the two. It's not a silver platter, it's a red herring.

To simplify the problem, try the experiment with just one frequency. The
Doppler shift, if is occurring, should distort a single-frequency waveform
by compressing the slope as the piston moves forward, and stretching the
slope as the piston moves backward. But we know that this does not happen
until the motion is so extreme that the air in front of the piston becomes
inelastic.

By the way, we'll know when we have the right solution when we have a set of
formulas that can accurately predict how much Doppler shift will occcur, and
then you can reliably measure the effect experimentally. The measured and
predicted effect must agree to a reasonable degree of accuracy, otherwise,
you simply don't have the right solution. AFAIK, this hasn't happened yet on
rec.audio.tech, which is the only thread I've been following.

It does if you replace the constant velocity with the varying velocity of the
cone, which is a trivial derivation and insertion. Duh!

That's simply wrong.

Not according to the gentleman who claims he's actually performed the
measurements.


"You people" are amazing. You want an instant answer to a question without
having to reason it through. And if you don't like the answer -- regardless
of
how well-reasoned it is -- you reject it.

With all due respect, I'm afraid you are out of your depth
in your reasoning on this problem.

Tell that to the people who agree with my reasoning.

I have a degree in electrical engineering. Which doesn't prove anything, of
course. But I remain amazed at the number of people who have a degree in XYZ --
and don't understand it worth a damn.

It does if you replace the constant velocity with the varying velocity
of the cone, which is a trivial derivation and insertion. Duh!

Be careful... If you setup the problem wrong, you'll come to the wrong
conclusion. One radiator is emitting two frequencies coupled to the
same air mass isn't the same as one radiator moving about inside an
air mass, which is what the Doppler formula is about. The vs term in
the Doppler formula isn't radiating energy or coupled to the air mass.

You are overanalyzing the obvious.


If the low frequency is coupled to the air mass in such a way that it is
radiating sound as effiently as it is at the higher frequencies, the energy
transfer is different.

The energy transfer produced by the LF movement of the cone has NOTHING to do
with the analysis of the problem, any more than the movement of the surrounding
air that "sticks" to the train.


If the radiator is just "flopping around" at the lower frequency without
creating sound waves, the higher frequency will be Doppler-shifted.

And what does the audibility of the LF movement of the driver have to do with
whether Doppler shift is created? NOTHING WHATEVER.

Are you suggesting that if our hypothetical train started oscillating on the
track at (oh) 100 Hz, at an average linear speed of 100 mph (think of the energy
required to do that!), we would suddenly STOP hearing a Doppler shift from its
whistle? Of course not! We would would hear it, and it would be modulated at 100
Hz.


Bingo! I don't think anyone on this thread (at least in rec.audio.tech) has
yet presented the fundamental physics relating to this problem so no one
really knows that they're talking about (including myself -- no offense).

Agreed. But I'm sticking by my analysis.

My favorite quote of Dr. Edwin H. Land goes as follows -- "We know all the
answers -- we just haven't asked the right questions." That is what science is
all about.

The reason your analysis is wrong is because YOU'RE NOT ASKING THE RIGHT
QUESTIONS.

The OP experiment (a high-frequency radiator mounted on a low-frequency,
non-radiating platform) are not the same conditions as a loudspeaker (a
high-frequency radiator mounted on a low-frequency, *radiating* platform).
You can't separate the two. It's not a silver platter, it's a red herring.

That's precisely the point -- it IS the same thing.

My point about superposition refers the loudspeaker cone itself. Assuming the
mechanism is reasonably linear, the HF movement of the cone has wholly
independent of the LF movement. That's why you can analyze the system as a HF
source "moved" by the low-frequency motion of the cone.


To simplify the problem, try the experiment with just one frequency. The
Doppler shift, if is occurring, should distort a single-frequency waveform
by compressing the slope as the piston moves forward, and stretching the
slope as the piston moves backward. But we know that this does not happen
until the motion is so extreme that the air in front of the piston becomes
inelastic.

Who says this doesn't occur? Has anyone ever measured a single-tone output to
see if there's any phase modulation?


As I said, I hate to appeal to authority. But I'm going to call Dr. Allen Hill
and see if he has any thoughts on the subject. I'm sure he'll have an elegant,
incisive explanation.

"William Sommerwerck" wrote in message
...
It does if you replace the constant velocity with the varying velocity
of the cone, which is a trivial derivation and insertion. Duh!

Be careful... If you setup the problem wrong, you'll come to the wrong
conclusion. One radiator is emitting two frequencies coupled to the
same air mass isn't the same as one radiator moving about inside an
air mass, which is what the Doppler formula is about. The vs term in
the Doppler formula isn't radiating energy or coupled to the air mass.

You are overanalyzing the obvious.

Am I? I think the fact that the lower frequency of a loudspeaker is also
radiating energy into the air as sound completely changes the conditions.
It's a different experiment.

If the low frequency is coupled to the air mass in such a way that it is
radiating sound as effiently as it is at the higher frequencies, the
energy
transfer is different.

The energy transfer produced by the LF movement of the cone has NOTHING to
do
with the analysis of the problem, any more than the movement of the
surrounding
air that "sticks" to the train.


If the radiator is just "flopping around" at the lower frequency without
creating sound waves, the higher frequency will be Doppler-shifted.

And what does the audibility of the LF movement of the driver have to do
with
whether Doppler shift is created? NOTHING WHATEVER.

The audibility doesn't enter into it. It has to do with whether the motion
is creating sound waves or not. Don't you think conditions will be different
if LF energy is being pumped into the surrounding air as sound, instead of
just creating a gentle breeze?

Are you suggesting that if our hypothetical train started oscillating on
the
track at (oh) 100 Hz, at an average linear speed of 100 mph (think of the
energy
required to do that!), we would suddenly STOP hearing a Doppler shift from
its
whistle? Of course not! We would would hear it, and it would be modulated
at 100
Hz.

I didn't say that. Instead, replace the train with a single piston
(loudspeaker) radiating multiple frequencies, that is what we're talking
about here. The purpose of the speaker is to radiate sounds into the air
over it's usable frequency response. We're trying to prove or disprove the
hypothesis that the any of the radiated frequencies interact in a Doppler
ralationship.

Bingo! I don't think anyone on this thread (at least in rec.audio.tech)
has
yet presented the fundamental physics relating to this problem so no one
really knows that they're talking about (including myself -- no offense).

Agreed. But I'm sticking by my analysis.

I think it's safe to do that until someone presents an alternative theory
that agrees with experimental data. My objection to the OP experiment is
that it's comparing apples & oranges.

My favorite quote of Dr. Edwin H. Land goes as follows -- "We know all the
answers -- we just haven't asked the right questions." That is what
science is
all about.

The reason your analysis is wrong is because YOU'RE NOT ASKING THE RIGHT
QUESTIONS.

We'll know that when we have a set of equations that predict the same amount
of Doppler shift that we can reliably measure experimentally, using a
loudspeaker, not an emitter radiating from a non-radiating platform.

William Sommerwerck wrote:

I don't think you can do it. Your prior explanation about using the standard
Doppler Effect formula does not apply because it assumes a constant linear
motion and a single frequency. It does not handle oscillating motion or
multiple frequencies.


It does if you replace the constant velocity with the varying velocity of the
cone, which is a trivial derivation and insertion. Duh!

I must be a glutton for punishment, but consider this, William.

You have a system in a black box, let's make it an arbitary
network of R, L, and C components, lumped and distributed.

Let that box have two inputs and an output. Run a series of
experiments with one input held at a constant value and
anything you like applied to the other. From this is is not
at all difficult to find an expression that describes the
behavior of the black box for any such signals.

Now instead of holding the one input constant, let's apply a
dynamic signal to it. Will the expression we found for the
cases where it was held constant apply to this case? What
if the first component on the input that is held constant
when determining the behavior were a series capacitor?

This is exactly analogous to the situation we have in trying
to simply plug a time varying parameter into an expression
that describes what happens when that parameter is static.


Bob
--

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

A. Einstein

"William Sommerwerck" wrote in message
...
The OP experiment (a high-frequency radiator mounted on a low-frequency,
non-radiating platform) are not the same conditions as a loudspeaker (a
high-frequency radiator mounted on a low-frequency, *radiating*
platform).
You can't separate the two. It's not a silver platter, it's a red
herring.

That's precisely the point -- it IS the same thing.

You'll have to convince me of that. Predict the effect mathemematically,
then measure the same results with a loudspeaker.

My point about superposition refers the loudspeaker cone itself. Assuming
the
mechanism is reasonably linear, the HF movement of the cone has wholly
independent of the LF movement. That's why you can analyze the system as a
HF
source "moved" by the low-frequency motion of the cone.


To simplify the problem, try the experiment with just one frequency. The
Doppler shift, if is occurring, should distort a single-frequency
waveform
by compressing the slope as the piston moves forward, and stretching the
slope as the piston moves backward. But we know that this does not happen
until the motion is so extreme that the air in front of the piston
becomes
inelastic.

Who says this doesn't occur? Has anyone ever measured a single-tone output
to
see if there's any phase modulation?

Predict the effect mathemematically, then measure the same results with a
loudspeaker.

As I said, I hate to appeal to authority. But I'm going to call Dr. Allen
Hill
and see if he has any thoughts on the subject. I'm sure he'll have an
elegant,
incisive explanation.

Michael W. Ellis wrote:

"William Sommerwerck" wrote in message
...
I can't tell from whence William posts, so I'll continue the cross-posting.

P L E A S E S T O P C R O S S - P O S T I N G TO

ALT....ACOUSTICS.

W E D O N O T N E E D T H I S. ! ! ! ! !

Have a good day,

Angelo Campanella

"Ron Hubbard" wrote in message ...

You know, you seem to say that to a lot of people as if you've never heard
the expression, "Put up or shut up."
Why don't you try that sometime; I'm sure it'll be a novel experience for
you.

A truly thoughtful and brilliant assessment, Ron. Take another drink
and go to sleep. When you wake up, take a bath, and put on some
clothes and have a meal consisting of solid food for a change. Then
put that bathrobe that you have been wearing for several months
straight, while watching all those soaps, into the wash. If you don't
have a washing machine, then at least soak it in the toilet for a few
hours before you put it back on. Then, before you hit the bottle
again, and while you are still partially lucid, read the thread which
I initiated entitled "Experimental Evidence for Dynamic Doppler
Shift." Finally, since everyone already knows that you have nothing
to "put up" I suggest that you follow your own advice and just "shut
up."

Karl Uppiano wrote:
"Ken Plotkin" wrote in message
...

On Sat, 21 Aug 2004 04:26:53 -0700, "Ron Hubbard"
wrote:


You know, you seem to say that to a lot of people as if you've never heard
the expression, "Put up or shut up."
Why don't you try that sometime; I'm sure it'll be a novel experience for
you.

Seems to me that Gary has "put up" plenty of times. Even on this
topic, he's taken the time to perform an experiment and report the
results. I think his posts have come within a hair of handing
everyone the answer on a silver platter.


The OP experiment (a high-frequency radiator mounted on a low-frequency,
non-radiating platform) are not the same conditions as a loudspeaker (a
high-frequency radiator mounted on a low-frequency, *radiating* platform).
You can't separate the two. It's not a silver platter, it's a red herring.

To simplify the problem, try the experiment with just one frequency. The
Doppler shift, if is occurring, should distort a single-frequency waveform
by compressing the slope as the piston moves forward, and stretching the
slope as the piston moves backward. But we know that this does not happen
until the motion is so extreme that the air in front of the piston becomes
inelastic.




Exactly.

Ian

That's precisely the point -- it IS the same thing.

You'll have to convince me of that. Predict the effect mathemematically,
then measure the same results with a loudspeaker.

It is not a question of mathematical prediction -- it is a question of
understanding the basic principles involved.

"William Sommerwerck" wrote in message
...
That's precisely the point -- it IS the same thing.

You'll have to convince me of that. Predict the effect mathemematically,
then measure the same results with a loudspeaker.

It is not a question of mathematical prediction -- it is a question of
understanding the basic principles involved.

How can you say you understand the basic physical principles involved if you
cannot describe it with a predictive mathematical model?
What's the point of a hypothesis that doesn't predict what will happen
experimentally by the amount and in the direction you predicted?

It is not a question of mathematical prediction -- it is a
question of understanding the basic principles involved.

How can you say you understand the basic physical principles
involved if you cannot describe it with a predictive mathematical model?

Well, I did supply a model -- which you rejected.

I don't have to have a formula for Doppler shift to understand that it exists,
and the mechanism that produces it.

Maxwell "understood" electromagnetics before he produced the equations that
describe it.

Karl Uppiano wrote:

The reason your analysis is wrong is because YOU'RE NOT ASKING THE RIGHT
QUESTIONS.


We'll know that when we have a set of equations that predict the same amount
of Doppler shift that we can reliably measure experimentally, using a
loudspeaker, not an emitter radiating from a non-radiating platform.

And that's going to be a really good trick and one well
worth working on. Consider for example a piston standing
alone in the air. Surround it by a circular baffle. The
on-axis Doppler distortion (the entire spatial function for
that matter) characteristics are going to change consderably
as we increase the diameter of the baffle from that of the
piston to infinity.

The best we are going to be able to do with this problem is
analyze it for various specific cases. We already know what
happens with a piston in a tube and it is likely that a
quantitative on-axis solution that is a function of the
diameter of the piston, the diameter of the baffle and the
distance from it could be found. A solution that describes
what would be observed with this configuration at any point
in space is probably a _lot_ harder. Either might be a good
undergrad or masters thesis if only for the purpose of
establishing the signifigance of the phenomenon as compared
to other things.

What might occur in a room from a speaker in a cabinet
boggles the mind.


Bob
--

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

A. Einstein

Angelo Campanella wrote:

Michael W. Ellis wrote:

"William Sommerwerck" wrote in message
...
I can't tell from whence William posts, so I'll continue the
cross-posting.


P L E A S E S T O P C R O S S - P O S T I N G TO

ALT....ACOUSTICS.

W E D O N O T N E E D T H I S. ! ! ! ! !

If it doesn't interest you, kill the thread.


Bob
--

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

A. Einstein

"William Sommerwerck" wrote in message
...
It is not a question of mathematical prediction -- it is a
question of understanding the basic principles involved.

How can you say you understand the basic physical principles
involved if you cannot describe it with a predictive mathematical model?

Well, I did supply a model -- which you rejected.

I questioned it -- I didn't reject it, but I will reject it if it cannot be
relied upon to experimentally produce the predicted effects in the amounts
predicted.

I don't have to have a formula for Doppler shift to understand that it
exists,
and the mechanism that produces it.

Well, I do. Otherwise, it's just someone's unsubstantiated claim. Mind you,
I'm not denying the Doppler effect, or the equations that describe it,
because the fact that the equations can be used to predict experimental
results with good accuracy prove the understanding and the mathematical
model are correct.

I'm waiting for experimental proof that a *loudspeaker* exhibits the same
phenomenon for the same reasons in the predicted amounts. If that doesn't
happen, the model and thus the hypothesis is flawed, and need to be
revisited.

Maxwell "understood" electromagnetics before he produced the equations
that
describe it.

I wouldn't say he had a complete understanding until he had the equations.
Before that, it was just a guess, and he had no way to prove correctness. We
didn't get radio and practical electric motors until we had the equations.

I saw a good description of the scientific method today, and I think it's
quite appropriate in this discussion:

==========

The Scientific Method

There is no canonical representation of the scientific method. Different
sources will explain it in different ways, but they are all referring to the
same logical process. For the purposes of this discussion, I will define the
scientific method as comprising the following activities repeated in a
cyclic manner:

Model - Form a simplified model of a system by drawing general conclusions
from existing data.

Predict - Use the simplified model to make a specific prediction about how
the system will behave when subject to particular conditions.

Test - Test the prediction by conducting an experiment.

If the test confirms our prediction, we return to step 2 and make a new
prediction based upon the same model. Otherwise, we return to step 1 and
revise our model so that it accounts for the results of our most recent test
(and all preceding tests).

==========

Full text and attribution he
http://www.hacknot.info/hacknot/action/showEntry?eid=64

"William Sommerwerck" wrote in message


To simplify the problem, try the experiment with just one frequency.
The Doppler shift, if is occurring, should distort a
single-frequency waveform by compressing the slope as the piston
moves forward, and stretching the slope as the piston moves
backward. But we know that this does not happen until the motion is
so extreme that the air in front of the piston becomes inelastic.

Who says this doesn't occur? Has anyone ever measured a single-tone
output to see if there's any phase modulation?

IME a nasty experiment because the usual means of eliminating AM distortion
(bandpass, then limit or clip) aren't effective.

Take a 50 Hz wave modulating itself. The first set of sidebands are at 0
(DC) and 100 Hz. The 100 Hz sideband and others above the carrier coincides
with the harmonics created by limiting or clipping. The DC offset would be a
pulse that might be detectable if the signal were gated at a regular rate,
but the experimental data at hand was not made that way.

Bob Cain wrote:

Let that box have two inputs and an output. Run a series of experiments
with one input held at a constant value

For the course of a set of measurements. It can then be
changed to another constant value for the next set of
measurements.

and anything you like applied to
the other. From this is is not at all difficult to find an expression
that describes the behavior of the black box for any such signals.


Bob
--

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

A. Einstein

"Karl Uppiano" writes:
[...]
Maxwell "understood" electromagnetics before he produced the equations
that
describe it.

I wouldn't say he had a complete understanding until he had the equations.
Before that, it was just a guess, and he had no way to prove correctness. We
didn't get radio and practical electric motors until we had the equations.

I agree 1000 percent. Mathematics is discovered, not invented.
--
% Randy Yates % "I met someone who looks alot like you,
%% Fuquay-Varina, NC % she does the things you do,
%%% 919-577-9882 % but she is an IBM."
%%%% % 'Yours Truly, 2095', *Time*, ELO
http://home.earthlink.net/~yatescr

On Sat, 21 Aug 2004 17:38:01 GMT, "Karl Uppiano"
wrote:

The OP experiment (a high-frequency radiator mounted on a low-frequency,
non-radiating platform) are not the same conditions as a loudspeaker (a
[snip]

And the shaft in Gary's experiment does not radiate because...?

To simplify the problem, try the experiment with just one frequency. The
[snip]

I look forward to seeing you post your results.

Ken Plotkin

"Ken Plotkin" wrote in message
...
On Sat, 21 Aug 2004 17:38:01 GMT, "Karl Uppiano"
wrote:

The OP experiment (a high-frequency radiator mounted on a low-frequency,
non-radiating platform) are not the same conditions as a loudspeaker (a
[snip]

And the shaft in Gary's experiment does not radiate because...?

Because it isn't efficiently coupled to the air at the frequency involved.
Any actual acoustical radiation due to the linear motor at the low frequency
would be negligible.

To simplify the problem, try the experiment with just one frequency. The
[snip]

I look forward to seeing you post your results.

Don't hold your breath. I have a day job. The suggestion was rhetorical,
since I think either effect would be based on the same physical processes,
and you could remove a frequency term from the equations.

"Randy Yates" wrote in message


"Karl Uppiano" writes:
[...]
Maxwell "understood" electromagnetics before he produced the
equations that describe it.

Yes, but we had electricity and some proficiency with it, well before
Maxwell.

I wouldn't say he had a complete understanding until he had the
equations. Before that, it was just a guess, and he had no way to
prove correctness.

But, you don't need a lot of correctness to get many technologies to work.

We didn't get radio

Arguably, we had radio transmission and reception the first time someone
noticed a symathetic reaction to an electrical discharge someplace else,
even just the other side of the table.

and practical electric motors until we had the equations.

Now we can argue about how practical an electrical motor has to be, to be
truely practical.

I agree 1000 percent. Mathematics is discovered, not invented.

But technology seems to grow in only rough parallel with the application of
math to it. But not necessarily in perfect synch.

Maxwell "understood" electromagnetics before
he produced the equations that describe it.

I wouldn't say he had a complete understanding until he had the equations.
Before that, it was just a guess, and he had no way to prove correctness.
We didn't get radio and practical electric motors until we had the equations.

I agree 1000 percent. Mathematics is discovered, not invented.

With whom?

Scientists often have intuitions about what is or is not the correct explanation
or model of something, before they develop a mathematical model.

Newton's discovery of universal gravitation was an insight that had nothing to
do with mathematics. The same is true of Einsteinian relativity.

Many other examples in math, science, and engineering can be given.

There is nothing wrong with intuition or "guessing."

In rec.audio.pro,
rec.audio.tech,
alt.music.home-studio and
alt.sci.physics.acoustics,

{ is it just me or is the number of group in this thread growing? }

"William Sommerwerck" wrote:

...

{ lots of back-and-forth with Arny snipped }

The idea that a pure sine wave signal Doppler-phase-modulates ITSELF is one that
I'm trying to digest at the moment.

Here's my description: At the positive peak of the waveform the
cone is closer to the receiver (we're of course presuming the receiver
is in front of the driver, not to the side or back) than at the
negative peak of the waveform. Due to the speed of sound, the receiver
must 'hear' the positive peak earlier than it would from a cone
reproducing the same sine at a lower volume (shorter cone excursion),
and likewise the negative peak takes longer to get to the receiver
than of it were at a lower volume.

For visualization of the waveshape, it helps to have played around
with a Yamaha DX-7 (oscillator at f=1, FM modulator also f=1, and vary
the amount of modulation) and a Casio CZ-101 (uses phase modulation,
which is similar to the FM case with osc and mod at 1), looking at the
output with an oscilloscope.

It would be interesting to calculate what a sine wave of a couple
of kHz and a peak-to-peak cone excursion of a couple of inches would
'sound like' at a fixed receiver. Of course, since the cone movement
is a substantial fraction of the speed of sound, a voice coil and
paper cone wouldn't work at that frequency and excursion, but as I've
suggested before, if you took the head of a gas engine and drove the
crank 120,000RPM (drive it with a running engine or high-power
electric motor, geared up appropriately), probably the piston would
stay connected long enough to demonstrate the effect. For extended
engine life, make sure there's adequate oil in the oilpan.

-----
http://mindspring.com/~benbradley

On Sat, 21 Aug 2004 18:03:40 -0400, Bob Cain wrote
(in article ):



Angelo Campanella wrote:

Michael W. Ellis wrote:

"William Sommerwerck" wrote in message
...
I can't tell from whence William posts, so I'll continue the
cross-posting.


P L E A S E S T O P C R O S S - P O S T I N G TO

ALT....ACOUSTICS.

W E D O N O T N E E D T H I S. ! ! ! ! !

If it doesn't interest you, kill the thread.


Bob


Hey,

Isn't it on topic? You Go Bob.

Ty Ford



-- Ty Ford's equipment reviews, audio samples, rates and other audiocentric
stuff are at www.tyford.com

Ty Ford wrote:


Hey,

Isn't it on topic?

Seems like an audio/acoustic topic to me.

You Go Bob.

Huh?


Bob
--

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

A. Einstein

Karl Uppiano wrote:

"Ken Plotkin" wrote in message
...

On Sat, 21 Aug 2004 17:38:01 GMT, "Karl Uppiano"
wrote:


The OP experiment (a high-frequency radiator mounted on a low-frequency,
non-radiating platform) are not the same conditions as a loudspeaker (a

[snip]

And the shaft in Gary's experiment does not radiate because...?


Because it isn't efficiently coupled to the air at the frequency involved.
Any actual acoustical radiation due to the linear motor at the low frequency
would be negligible.

What he said.


Bob
--

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

A. Einstein

On Sun, 22 Aug 2004 04:14:44 GMT, "Karl Uppiano"
wrote:


Because it isn't efficiently coupled to the air at the frequency involved.
Any actual acoustical radiation due to the linear motor at the low frequency
would be negligible.
[snip]

Let's say someone with more than a rhetorical interest were to
calculate the flow field around the piston and around the speaker
cone, and showed there was a larger flow field around the cone.

That flow field is moving in the same direction as the cone. Any
Doppler effect would therefore be enhanced: the convection speed of
the local flow field is added to the speed of the piston or cone.
Thus, not only does Gary's experiment demonstrate the doppler shift,
but it shows the minumum potential shift.

I am really puzzled as to why people are arguing that this Doppler
shift does not occur. If you view things one dimensionally (as
everyone has), it's straight high school geometry to figure it. If
the local flow of a speaker cone somehow defeats it, then why doesn't
the local flow around a train defeat the Doppler shift of a train
whistle?

Ken Plotkin

"Arny Krueger" wrote in message
...
"Randy Yates" wrote in message


"Karl Uppiano" writes:
[...]
Maxwell "understood" electromagnetics before he produced the
equations that describe it.

Yes, but we had electricity and some proficiency with it, well before
Maxwell.

I wouldn't say he had a complete understanding until he had the
equations. Before that, it was just a guess, and he had no way to
prove correctness.

But, you don't need a lot of correctness to get many technologies to work.

But if we're trying to get at the truth about a hypothesis, we must prove
its correctness. If we just want some sub-optimal gadget to work, I guess
there's room for a lot of fudging. If we're trying to put a communications
satellite in orbit and use it for GPS, we need a very high degree of
correctness.

We didn't get radio

Arguably, we had radio transmission and reception the first time someone
noticed a symathetic reaction to an electrical discharge someplace else,
even just the other side of the table.

We had the beginnings of knowledge. We had "wireless" communication. We
didn't have efficient transmitters, decent antenna designs. Those things
didn't come along until we really understood what Maxwell's equations were
telling us, so we could design something we knew would work without a lot of
trial and error.

and practical electric motors until we had the equations.

Now we can argue about how practical an electrical motor has to be, to be
truely practical.

Compare at the difference in size of a 1HP electric motor from the early
20th to one built today. When we have the correct tools and mathematical
models, things get much more practical.

I agree 1000 percent. Mathematics is discovered, not invented.

But technology seems to grow in only rough parallel with the application
of math to it. But not necessarily in perfect synch.

By the way, my reply wants to cross-post to about 5 different news groups.
Is this really necessary? Which one is the most appropriate?

"Ken Plotkin" wrote in message
...
On Sun, 22 Aug 2004 04:14:44 GMT, "Karl Uppiano"
wrote:


Because it isn't efficiently coupled to the air at the frequency involved.
Any actual acoustical radiation due to the linear motor at the low
frequency
would be negligible.
[snip]

Let's say someone with more than a rhetorical interest were to
calculate the flow field around the piston and around the speaker
cone, and showed there was a larger flow field around the cone.

Let's just do the experiment using a real loudspeaker that is efficiently
radiating the two frequencies in question. Then repeat the experiment with
the loudspeaker not radiating the lower frequency (i.e., take the speaker
out of its baffle, or use a much lower frequency).

That flow field is moving in the same direction as the cone. Any
Doppler effect would therefore be enhanced: the convection speed of
the local flow field is added to the speed of the piston or cone.
Thus, not only does Gary's experiment demonstrate the doppler shift,
but it shows the minumum potential shift.

A flow field (gentle breeze) is not the same thing as propagating audio
energy into the air (sound).

I am really puzzled as to why people are arguing that this Doppler
shift does not occur. If you view things one dimensionally (as
everyone has), it's straight high school geometry to figure it. If
the local flow of a speaker cone somehow defeats it, then why doesn't
the local flow around a train defeat the Doppler shift of a train
whistle?

Because a flow field isn't sound. It's just wind.

Ken Plotkin

Ken Plotkin wrote:

I am really puzzled as to why people are arguing that this Doppler
shift does not occur.

I'm no longer arguing that in a general sense and haven't
for a week or so. Yes, I started there because it doesn't
exist for a piston in a tube (or the infinite vibrating
plane) but I was dead wrong in my initial take that that
proved it's general non-existance. All it showed was the
falacy of the standard description of its cause.

If you view things one dimensionally (as
everyone has), it's straight high school geometry to figure it. If
the local flow of a speaker cone somehow defeats it, then why doesn't
the local flow around a train defeat the Doppler shift of a train
whistle?

Local flow around is one of the things that will exacerbate
it, not defeat it.


Bob
--

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

A. Einstein

"Karl Uppiano" wrote in message

"Arny Krueger" wrote in message
...
"Randy Yates" wrote in message


"Karl Uppiano" writes:
[...]
Maxwell "understood" electromagnetics before he produced the
equations that describe it.

Yes, but we had electricity and some proficiency with it, well before
Maxwell.

I wouldn't say he had a complete understanding until he had the
equations. Before that, it was just a guess, and he had no way to
prove correctness.

But, you don't need a lot of correctness to get many technologies to
work.

But if we're trying to get at the truth about a hypothesis, we must
prove its correctness.

Agreed. However, in the real world of times past, the most important
hypothesis was "I think it works!"

If we just want some sub-optimal gadget to
work, I guess there's room for a lot of fudging.

Most new gadgets start out pretty suboptimal.

If we're trying to
put a communications satellite in orbit and use it for GPS, we need a
very high degree of correctness.

True, but the correctness is in the area of orbital mechanics, which is
simple tech and old tech.

We didn't get radio

Arguably, we had radio transmission and reception the first time
someone noticed a symathetic reaction to an electrical discharge
someplace else, even just the other side of the table.

We had the beginnings of knowledge. We had "wireless" communication.
We didn't have efficient transmitters, decent antenna designs. Those
things didn't come along until we really understood what Maxwell's
equations were telling us, so we could design something we knew would
work without a lot of trial and error.

That was some distance down the line from the first time it worked.

and practical electric motors until we had the equations.

Now we can argue about how practical an electrical motor has to be,
to be truely practical.

Compare at the difference in size of a 1HP electric motor from the
early 20th to one built today. When we have the correct tools and
mathematical models, things get much more practical.

Frankly, materials science, not Maxwell's equations dominated progress in
that area.

I agree 1000 percent. Mathematics is discovered, not invented.

But technology seems to grow in only rough parallel with the
application of math to it. But not necessarily in perfect synch.

By the way, my reply wants to cross-post to about 5 different news
groups. Is this really necessary? Which one is the most appropriate?

If we change it at this point, we break a lot of threads.

On Sun, 22 Aug 2004 18:40:49 GMT, "Karl Uppiano"
wrote:

Because a flow field isn't sound. It's just wind.

If you want to look at it that way, sure. But either way there is a
velocity and sound on it is convected.

Bob Cain wrote:



Ken Plotkin wrote:

I am really puzzled as to why people are arguing that this Doppler
shift does not occur.


I'm no longer arguing that in a general sense and haven't for a week or
so. Yes, I started there because it doesn't exist for a piston in a
tube (or the infinite vibrating plane) but I was dead wrong in my
initial take that that proved it's general non-existance. All it showed
was the falacy of the standard description of its cause.

If you view things one dimensionally (as
everyone has), it's straight high school geometry to figure it. If
the local flow of a speaker cone somehow defeats it, then why doesn't
the local flow around a train defeat the Doppler shift of a train
whistle?


Local flow around is one of the things that will exacerbate it, not
defeat it.

That assumes local flow of sound energy, not air.


Bob
--

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

A. Einstein

On Sun, 22 Aug 2004 16:09:25 -0700, Bob Cain
wrote:


That assumes local flow of sound energy, not air.

Don't look now, but when sound energy is flowing the air is moving
back and forth. Surprisingly enough, it moves back and forth in phase
with the sound.

Ken Plotkin wrote:

On Sun, 22 Aug 2004 16:09:25 -0700, Bob Cain
wrote:



That assumes local flow of sound energy, not air.


Don't look now, but when sound energy is flowing the air is moving
back and forth. Surprisingly enough, it moves back and forth in phase
with the sound.

Really?! Amazing, that. Whoda thunk it.

I was distinguishing radiation flow from bulk flow and if
you call the "sound" the pressure then it is only really in
phase with the motion in some special circumstances, like
the piston in a terminated or infinite tube.


Bob
--

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

A. Einstein