Jim Carr wrote:


With that said, I respectfully disagree with #1. :-)

Respectfully accepted as such. :-)


First, the piston will stop moving at some point and return to its starting
position. The air molecules will keep moving until they run out of energy.

No, I specified that the piston have infinite compliance and
zero mass and I should have added, no friction. If that is
true, it will follow the motion of the air just because
there is no reason for it not to.

Piston motion is in response to the difference in pressure
on each side. Since mass, compliance and friction are not
restraining it, it moves so that the pressure differential
is always zero. To do that, it must move with the air
particles because not doing so is the only way to generate a
pressure differential. This is a key point.

This part is only gendanken to come up with a signal to be
reproduced. If the driven, reproducing piston contains
mass, non-zero compliance or friction, which are all linear,
then the driving signal can be pre-compensated by the
inverse of the resulting mechanical impedence so as to
eliminate their effects and result in the motion required by
the signal. These things are all logically between the
signal and the piston/air interface so have no effect on
what happens there in the sense of a distortion mechanism.


Second, think about there being two pulses. If the second pulse arrives
after the piston returns to its starting position, then the duration between
the pulses will be exactly known. Therefore, the frequency of the pulses is
exactly known. If the second pulse arrives while the piston is still moving
forward with the first pulse, then the second pulse strikes the piston while
it's in a different position than when the first pulse struck it. That pulse
has traveled farther than in our first scenario. If you were to measure the
duration between the pulses in this scenario, it would be greater.
Therefore, a form of distortion is introduced.

If the principle is true for any arbitrary pulse, and that
was a starting propositon, then it is true for the
superpostion of any number of pulses because any
superposition is just another arbitrary pulse.


Bob
--

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

A. Einstein

Jim Carr wrote:

Disclaimer: I am *not* stating anything here as an expert in this field.

You will be when I'm done with you. :-)


Bob
--

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

A. Einstein

"Bob Cain" wrote in message
...
First, the piston will stop moving at some point and return to its
starting
position. The air molecules will keep moving until they run out of
energy.

No, I specified that the piston have infinite compliance and
zero mass and I should have added, no friction. If that is
true, it will follow the motion of the air just because
there is no reason for it not to.

Let's start here. Air is made up of a bunch of loosely packed molecules
constantly and randomly banging into one another. Am I correct?

If so, suppose I manage to start a single pulse by some method that is
hopefully immaterial. Air molecules start banging into each other in
essentially one direction. Now, I grant they spread out, but there is a
pattern when compared to the normal random collisions. Each collision uses
up some energy. Eventually there's not enough energy for any more
collisions. Would you agree or disagree that this happens?

If you agree, then we can say that a sound wave is not really a set of air
molecules going from point A to point B but rather *energy* traveling from
point A to point B through a series of air molecules colliding in an
identifiable pattern we call a wave. Can we agree on that? Again, I want to
repeat that I am simply building up a theory from a relatively small base of
knowledge and what I hope is some sound logic. If I sound condescending,
then I am doing so to myself, not you. I am trying to lay this out so *I*
understand what I'm talking about. :-)

So let's shove your piston in there. By definition the piston is not really
following the motion of the air because the air really isn't moving like a
breeze. It has to react to the energy hitting it just like the air molecules
do. Therefore, to say the piston "follows the motion of the air" is
imprecise.

What I think you are trying to say is that the piston is acted upon by the
energy of the sound wave in the *exact* same way as the air molecules. So,
how far does it move? The exact same distance as one molecule of air moves?
If so, I doubt we could induce a voltage in a coil.

Since we are in fact talking about inducing voltage in a coil and and in the
case of a speaker the subsequent movement of a piston in reaction to that
voltage, we have to include that parameter as part of the discussion.
Doppler distortion wouldn't exist if the piston *only* moved like a single
molecule.

The piston must move the coil to induce a voltage. It has to move a finite
and extremely limited distance compared to distance the energy from a sound
wave travels. The piston also must move backwards at some point otherwise it
would only react to the first pulse.

In my opinion there is no possible way to find a formula to describe Doppler
Distortion without these limiting factors of the piston. Without using any
formula I would say that Doppler Distortion comes about *because* the piston
moves a greater distance and at a slower speed than energy through the air
and because the piston also has a device which pulls it back to center
whereas the air molecules do not.

It sounds like you're trying to say that your imaginary piston (which can
never exist, BTW) would behave exactly as the air molecules do, therefore,
there is no distortion. Of course not. Your constraints on the piston
essentially describe a single molecule of air. There's no way to pick a
molecule of air and say that's distortion. The movement of the molecule as
the energy passes through it is what we're trying to measure in the first
place.

The reality is that the piston does *not* act like an air molecule, so you
need to look for a way to explain the vibration of the piston and contrast
that against the vibration of air molecules. It's that difference that
causes Doppler Distortion as I understand it.

"Bob Cain" wrote in message
...


Jim Carr wrote:

Disclaimer: I am *not* stating anything here as an expert in this field.

You will be when I'm done with you. :-)

LOL! You guys make me think, that's for sure. I contrast this against the
football newsgroup I'm in that spent the off-season arguing the question: If
you were filming Hillary Clinton swimming and you saw she was drowing, what
would you do?

On Fri, 6 Aug 2004 10:54:46 -0400, "Arny Krueger"
wrote:

"Don Pearce" wrote in message

On Fri, 6 Aug 2004 10:18:35 -0400, "Arny Krueger"
wrote:

"Don Pearce" wrote in message

On Fri, 6 Aug 2004 07:47:24 -0400, "Arny Krueger"
wrote:

The only way to verify this is to look at the phase as well as the
amplitude of the sidebands.

That's one way, but it's a very hard row for me to hoe.

So, you decline to believe that the relative amplitudes of the
sidebands are different and relevant, as the frequency has
increased?


No, not at all. But I am not convinced that with the complex
interactions of a speaker you can reach your conclusion as simply as
you have. Non-linearities of various orders can cause a
multiplication function which results in phase modulation. But to
put this down to Doppler effect is a leap too far for me.

I agree that the actual acoustical measurements may or may not show a
Doppler effect. At best the Doppler distortion is relatively small
in the face of the massive AM effects.

If I turn the volume up, the AM effects seem to get stronger, both
overall and proportionately. And, this is a relatively linear driver
being driven over a wider frequency range than it would be used in a
good design.

If I got anything worthwhile out of this, it is the concept of using
3 tones to separate AM distortion from FM distortion. But you still
need an underlying clear instance of FM distortion to make it worth
the trouble. I suspect that a lot of the purported jitter
measurements we've seen are actually pretty suspect because the
common measurements confuse AM and FM distortion.


Certainly in terms of spectrum, narrowband FM is virtually
indistinguishable from AM unless you can get at the relative phase of
the sidebands.

Measuring the phase of acoustical signals, and signals in general, can be a
vale of tears. I've played this game many times, and while I've had some
success, I feel like I earned it! ;-)

It appears that one can differentiate AM and FM based on the amplitudes of
the sidebands for carriers that have significantly different base
frequencies.

A given AM process will produce sidebands with the same amplitudes over a
wide variety of carrier frequencies. FM processes are very dependent on the
frequency of the carrier.

For a given rate of change in timing, the higher frequency carrier will show
a larger shift in frequency. This increases the Modulation Index, which is
the quotient of the maximum deviation/divided by the modulating frequency.
The higher modulation index increases the size and number of sidebands.
Therefore, higher frequency carriers will produce more sidebands and
sidebands that have a larger amplitude.

My Audition/CoolEdit simulations show this quite clearly.

But as for Doppler distortion. Do the sums, assuming a perfectly
linear driver (which should still show the phenomenon if it exists,
since it needs no non-linearity).

That would be a more complex theoretical exercise.

You will find that the sum of the
tones exactly matches what the trajectory of the cone should be to
prevent such distortion.

I don't see it. And as I've now pointed out several times, the JAES doesn't
seem to see it, either. IOW, there are a goodly number of refereed papers
that give abundant positive evidence that it does exist. I see that train
coming towards me, and I see that cone coming towards me!



OK, the definitive test has just occurred to me, and it is easy. Turn
the speaker through 90 degrees and make the test again. The motion of
the cone is now normal to the measuring axis and there can be no
doppler distortion. Anything that now remains is due to other effects.
What vanishes is possibly doppler.

d

Pearce Consulting
http://www.pearce.uk.com

Jim Carr wrote:

No, I specified that the piston have infinite compliance and
zero mass and I should have added, no friction. If that is
true, it will follow the motion of the air just because
there is no reason for it not to.


Let's start here. Air is made up of a bunch of loosely packed molecules
constantly and randomly banging into one another. Am I correct?

At the lowest level, but for the purposes of acoustics, and
other than in consideration of noise, they can be
statistically treated as a continuous compressible gas from
which the acoustic laws are derived. In brief you need not
consider the molecular compostion in working with its dynamics.

If you agree, then we can say that a sound wave is not really a set of air
molecules going from point A to point B but rather *energy* traveling from
point A to point B through a series of air molecules colliding in an
identifiable pattern we call a wave. Can we agree on that? Again, I want to
repeat that I am simply building up a theory from a relatively small base of
knowledge and what I hope is some sound logic. If I sound condescending,
then I am doing so to myself, not you. I am trying to lay this out so *I*
understand what I'm talking about. :-)

With that, I think you stated what I did above in a
different way. Yes I agree.


So let's shove your piston in there. By definition the piston is not really
following the motion of the air because the air really isn't moving like a
breeze. It has to react to the energy hitting it just like the air molecules
do. Therefore, to say the piston "follows the motion of the air" is
imprecise.

Not so. It is constrained by the condition that no pressure
differential, dP, is allowed across it because of its ideal
definition. If it did, it would accelerate at infinite
rate. A=dP*D/M. A is infinite because M is zero. D is the
diameter. The only way it can maintain that is to move with
the bulk velocity of the air so as to keep dP equal to zero.
Think of it as a compressible fluid. If you think of an
infinitessimal volume of that fluid, the piston will move in
concert with those volumes that are in contact with it. To
do otherwise would create a pressure difference from one
side to the other and it would move to zero it without
delay. That's what it is doing, moving without delay to
keep the pressure differential at zero. Since it is never
at any other value than zero, it is moving precisely with
the bulk velocity of the air.

Since we are in fact talking about inducing voltage in a coil and and in the
case of a speaker the subsequent movement of a piston in reaction to that
voltage, we have to include that parameter as part of the discussion.

What parameter is that?


The piston must move the coil to induce a voltage. It has to move a finite
and extremely limited distance compared to distance the energy from a sound
wave travels. The piston also must move backwards at some point otherwise it
would only react to the first pulse.

We need not consider coils or voltages at the point of
determining the velocity of that ideal piston.


In my opinion there is no possible way to find a formula to describe Doppler
Distortion without these limiting factors of the piston. Without using any
formula I would say that Doppler Distortion comes about *because* the piston
moves a greater distance and at a slower speed than energy through the air
and because the piston also has a device which pulls it back to center
whereas the air molecules do not.

But you can't say that without writing some formula. I say
it can't be written because it would violate the conditions
I described which are due to physical laws.


It sounds like you're trying to say that your imaginary piston (which can
never exist, BTW)

Doesn't matter because if the ideal case can't generate
Doppler distortion then nothing can that contains linear
components of friction, mass and compliance. I showed how
their effects could be eliminated in the reproducer in the
post you are responding to. The ideal measuring device just
tells you what the velocity is without disturbing the
acoustic field it measures.

would behave exactly as the air molecules do, therefore,
there is no distortion. Of course not. Your constraints on the piston
essentially describe a single molecule of air. There's no way to pick a
molecule of air and say that's distortion. The movement of the molecule as
the energy passes through it is what we're trying to measure in the first
place.

To refute my argument you have to show that an ideal passive
piston wouldn't track the bulk velocity of the medium.
You don't need to interact with it in a signifigant way to
measure it's velocity, you could use a laser interferometer,
for example (which has in fact been proposed for a
microphone sensor.) All I've really described is a large,
ideal microphone.


The reality is that the piston does *not* act like an air molecule, so you
need to look for a way to explain the vibration of the piston and contrast
that against the vibration of air molecules. It's that difference that
causes Doppler Distortion as I understand it.

If you followed it, you should be able to see by now why it
would. Remember, we are considering the net effect of a
whole lot of these molecules.

If you won't accept any of these arguments would you accept
that there is some way in principle to measure the bulk
velocity without distrubing what you are measuring, at least
for all practical purposes? How about tracking the motion
of a smoke particle?

If you can then we can move on to the reproduction half of
the problem. It wasn't really necessasary to employ the
piston for measurement but it illustrates the principle of
reciprocity of measurement and transduction which is well known.


Bob
--

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

A. Einstein

Jim Carr wrote:

"Bob Cain" wrote in message
...


Jim Carr wrote:


Disclaimer: I am *not* stating anything here as an expert in this field.

You will be when I'm done with you. :-)


LOL! You guys make me think, that's for sure. I contrast this against the
football newsgroup I'm in that spent the off-season arguing the question: If
you were filming Hillary Clinton swimming and you saw she was drowing, what
would you do?

I give.


Bob
--

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

A. Einstein

"Bob Cain" wrote in message
...

LOL! You guys make me think, that's for sure. I contrast this against
the
football newsgroup I'm in that spent the off-season arguing the
question: If
you were filming Hillary Clinton swimming and you saw she was drowing,
what
would you do?

I give.

The general consensus was to let her drown. A good part of the crowd wanted
to rescue her, then shoot her.

Personal, I wanted to throw her a cigar shaped flotation device.

Jim Carr wrote:

"Bob Cain" wrote in message
...


LOL! You guys make me think, that's for sure. I contrast this against

the

football newsgroup I'm in that spent the off-season arguing the

question: If

you were filming Hillary Clinton swimming and you saw she was drowing,

what

would you do?

I give.


The general consensus was to let her drown. A good part of the crowd wanted
to rescue her, then shoot her.

Personal, I wanted to throw her a cigar shaped flotation device.

Actually, I'd rescue her and hope it made her horny. I've
always thought she was sorta cute. Of course a few laps on
the old treadmill at this point would help a bit but if
she's swimming maybe she's already made some progress in
that regard. :-)


Bob
--

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

A. Einstein

On Mon, 09 Aug 2004 02:31:20 -0700, Bob Cain
wrote:

Actually, I'd rescue her and hope it made her horny. I've
always thought she was sorta cute. Of course a few laps on
the old treadmill at this point would help a bit but if
she's swimming maybe she's already made some progress in
that regard. :-)

Here in the UK, we're ruled by a man who, 20 years ago, looked at
Cherie Booth across a crowded room and thought: "Now, there's a
good-looking woman!"

Worrying.

CubaseFAQ www.laurencepayne.co.uk/CubaseFAQ.htm
"Possibly the world's least impressive web site": George Perfect

"Don Pearce" wrote in message


OK, the definitive test has just occurred to me, and it is easy. Turn
the speaker through 90 degrees and make the test again. The motion of
the cone is now normal to the measuring axis and there can be no
doppler distortion. Anything that now remains is due to other effects.
What vanishes is possibly doppler.

Care to comment on the polar response of speakers at 90 degrees?

The word messy, comes to mind.

On Mon, 9 Aug 2004 08:00:19 -0400, "Arny Krueger"
wrote:

"Don Pearce" wrote in message


OK, the definitive test has just occurred to me, and it is easy. Turn
the speaker through 90 degrees and make the test again. The motion of
the cone is now normal to the measuring axis and there can be no
doppler distortion. Anything that now remains is due to other effects.
What vanishes is possibly doppler.

Care to comment on the polar response of speakers at 90 degrees?

The word messy, comes to mind.


Doesn't matter - it is what happens to the relative levels of the
distortion products as you shift the low frequency around that
matters.

d

Pearce Consulting
http://www.pearce.uk.com

On Mon, 09 Aug 2004 08:03:09 +0100, Don Pearce
wrote:


OK, the definitive test has just occurred to me, and it is easy. Turn
the speaker through 90 degrees and make the test again. The motion of
the cone is now normal to the measuring axis and there can be no
doppler distortion. Anything that now remains is due to other effects.
What vanishes is possibly doppler.


An interesting idea but taken to its logical conclusion might suggest
that there would be no sound either. If the sound diffracts then the
path taken by the 4kHz has to bend and the path length will change as
the speaker moves at 50 Hz.

On Mon, 09 Aug 2004 12:40:19 GMT, ow
(Goofball_star_dot_etal) wrote:

On Mon, 09 Aug 2004 08:03:09 +0100, Don Pearce
wrote:


OK, the definitive test has just occurred to me, and it is easy. Turn
the speaker through 90 degrees and make the test again. The motion of
the cone is now normal to the measuring axis and there can be no
doppler distortion. Anything that now remains is due to other effects.
What vanishes is possibly doppler.


An interesting idea but taken to its logical conclusion might suggest
that there would be no sound either. If the sound diffracts then the
path taken by the 4kHz has to bend and the path length will change as
the speaker moves at 50 Hz.

No - didn't understand any of that. Can you explain more fully?

d

Pearce Consulting
http://www.pearce.uk.com

On Sun, 08 Aug 2004 18:45:54 -0700, Bob Cain
wrote:


Well, I've asked for help on the general equation for pressure at
a point removed from an ideal piston in an infinite tube as a
function of the force applied to the piston that includes the
effects of Doppler distortion in alt.sci.physicw and on the
moderated group sci.physics.research where the real guns hang
out and there has been no answer.

What I've found is that any attempt to write the expression
from conditions at the interface results in a recursion or
infinite regress unless the term included to account for
the motion of the piston is set to zero. It's really tricky.

So let's look at an argument by reciprocity.

Ah, you are basing your argument on the system being linear with
reciprocity and superposition being applicable.

Assume an
acoustic pulse of any arbitrary shape running down the tube
with an ideal pistion (no mass, stiff, infinite compliance)
in place.

1. The piston will move exactly in step with the motion of
the air molecules as the pulse passes by it.

Now let's measure and record the velocity of that piston as
the pulse passes by. Next let's mount a voltage to velocity
transducer, again ideal with a zero mechanical impedence, on
the side of the piston from which the pulse came when we
measured it.

2. When we drive that piston so as to reproduce the velocity
that was recorded we will get the identical pulse propegating
off of it as originally measured.

3. Because air is air, the resulting pressure pulse will be
in phase with that velocity and given by p(t) = v(t) * Ra,
where Ra is the characteristic impedence or air, and that
pressure pulse will be identical to the one that the
measured pulse had.

Because this should be true with a pulse of any shape it will
be true of a supposition of any such pulses which implies that
it is true of any signal and is thus a linear transducer with
no distortion of any kind.



Circular. . .

"Goofball_star_dot_etal" wrote in message


On Mon, 09 Aug 2004 08:03:09 +0100, Don Pearce
wrote:

OK, the definitive test has just occurred to me, and it is easy. Turn
the speaker through 90 degrees and make the test again. The motion of
the cone is now normal to the measuring axis and there can be no
doppler distortion. Anything that now remains is due to other
effects. What vanishes is possibly Doppler.

An interesting idea but taken to its logical conclusion might suggest
that there would be no sound either. If the sound diffracts then the
path taken by the 4kHz has to bend and the path length will change as
the speaker moves at 50 Hz.

Exactly, and then some.

I think its pretty telling that I'm the only person on this thread who has
actually taken a look at the practical aspects of this problem. I've offered
to collect reasonable amounts of data for others to analyze, per other
people's specs, and post them for others to review and analyze.

I had no idea that $40 speaker drivers, MDF boxes, power amps, mic preamps
and $50 measurement mics were so dear! ;-)

In theory, an ideal piston produces no air pressure changes along its side
because there is no relative motion. Basically, the mic is looking at this
highly polished slab of material that whose perpendicular motion is almost
undetectable, except for real-world surface imperfections and friction.

Of course the mic still picks up some sound, but exactly where does it come
from? Is it being diffracted? It is being reflected by the room? All of the
above and perhaps more!

"Arny Krueger" wrote in message


"Goofball_star_dot_etal" wrote in message


I've got the radio if you get the urge to broadcast the raw data...

Yes Goofball, you do have those specialized programs that look at the phase
of sidebands, right?

Sounds like an idea. I'm going to try to not pull a John Atkinson
hide-the-data trick on you.

I collected the data at 16/44 to keep the data files a little shorter.

I didn't save the data from the two three-tone tests.

But I did this time.

I'm going to do several tests in quick succession so that
the acoustical setup remains the same.

OK, I redid the tests at 3 different levels, picked to be more
standard-like.

I just posted the revised graphic results and links to the raw test data
files at:

http://www.pcavtech.com/techtalk/doppler/

Enjoy!

I'll also try to do it when its acoustically quiet.

I wish.

"Arny Krueger" writes:

"Goofball_star_dot_etal" wrote in message


On Mon, 09 Aug 2004 08:03:09 +0100, Don Pearce
wrote:

OK, the definitive test has just occurred to me, and it is easy. Turn
the speaker through 90 degrees and make the test again. The motion of
the cone is now normal to the measuring axis and there can be no
doppler distortion. Anything that now remains is due to other
effects. What vanishes is possibly Doppler.

An interesting idea but taken to its logical conclusion might suggest
that there would be no sound either. If the sound diffracts then the
path taken by the 4kHz has to bend and the path length will change as
the speaker moves at 50 Hz.

Exactly, and then some.

I think its pretty telling that I'm the only person on this thread who has
actually taken a look at the practical aspects of this problem. I've offered
to collect reasonable amounts of data for others to analyze, per other
people's specs, and post them for others to review and analyze.

I had no idea that $40 speaker drivers, MDF boxes, power amps, mic preamps
and $50 measurement mics were so dear! ;-)

In theory, an ideal piston produces no air pressure changes along its side
because there is no relative motion. Basically, the mic is looking at this
highly polished slab of material that whose perpendicular motion is almost
undetectable, except for real-world surface imperfections and friction.

Of course the mic still picks up some sound, but exactly where does it come
from? Is it being diffracted? It is being reflected by the room? All of the
above and perhaps more!

An anechoic measurement would omit the reflected sources. This could be done
in an anechoic room or using specialized measurements like time-delay
spectrometry. How do they get those polar response curves of loudspeakers in
the magazines (where vertical and horizontal angular plots are usually shown
separately)?
--
Randy Yates
Sony Ericsson Mobile Communications
Research Triangle Park, NC, USA
, 919-472-1124

"Jim Carr" wrote in message news:JvERc.3628$yh.1495@fed1read05...
Let's start here. Air is made up of a bunch of loosely packed molecules
constantly and randomly banging into one another. Am I correct?

Yes, and, in fact, it can be considered NEARLY and ideal gas for
the purpose of most human-tolerable sound pressure levels, that is,
it can be considered a medium consisting of infinitesimally small
point objects engaged in (nearly) perfect elestic collisions,

If so, suppose I manage to start a single pulse by some method that is
hopefully immaterial. Air molecules start banging into each other in
essentially one direction. Now, I grant they spread out, but there is a
pattern when compared to the normal random collisions. Each collision uses
up some energy. Eventually there's not enough energy for any more
collisions. Would you agree or disagree that this happens?

Physics would disagree quite vehemently. The collisions themselves
are damned near perfectly lossless. Thus, the collisions themselves
dissipate essentially NO energy whatseoever.

Now, what DO you think happens to the energy?

If you agree, then we can say that a sound wave is not really a set of air
molecules going from point A to point B but rather *energy* traveling from
point A to point B through a series of air molecules colliding in an
identifiable pattern we call a wave.

WOW! What a neat f*cking idea! Analyzing sound based on the concepts
of the kinetic theory of gasses!

Keep going, gents, and you may well figure out why a substantial
portion of the sacrosanct "principles" of audio, notably a bunch
of religiously held believes by the high-end, is really a big
stinking crock of sh*t.

Okay, let's get back to it.

If you're assertion is that we're adding some energy to a group
of molecules, what do you think that means? What KIND of energy?
Well, according to you, these things are moving around and bumping
into each other. If you add energy to them by bumping into them,
what kind of energy are you adding to them. you have two choices:
kinietic or potential. (hint: it's kinetic because bumping into
makes them move a little faster).

Now, if you guessed "kinetic" then you're probably right. Now,
remeber back to your high-school physics class. By moving the piston
you've added some energy, and the average energy of our gas molecules
has gone up (we talk about the "average" because it makes no sense to
talk about one: one molecule does not propogate sound).

What's another name for the "average kinetic energy" of a gas?
(hint: it's spelled t-e-m-p-e-r-a-t-u-r-e).

So, if you now guessed temperature, you'd probably get a point for
that question. Fine, so pushing the piston in THAT direction raises the
temperature of the air, because it raises the temperature of the air,
because the two are saying EXACTLY the same thing. (and, if you wanted
to, you could say that it raises the average molecular velocity as
well, since, very simply, e = 1/2 mv^2. Given that each m is VERY
small, what do you think v is equal to at room temperature?)

Now, if I raise the temperture of a gas HERE, what do you think happens
to the gas THERE? (hint: think about how something wants to maintain
equilibrium with its surrounding). How do you think it will do this,
and how fast do you think it will do so?

So let's shove your piston in there. By definition the piston is not really
following the motion of the air because the air really isn't moving like a
breeze. It has to react to the energy hitting it just like the air molecules
do. Therefore, to say the piston "follows the motion of the air" is
imprecise.

The piston, if allowed to move, will do so ONLY if there is a net
force on it. Assume the gas currounding the piston is of uniform
composition and density, it can only do so if the average net force
of collisions on one side is gerater than that on the other, and,
given the assumptions of identical composition and density, can only
do so if the average collision velocity is different.

And since the everage kinetic energy of the gas geos as the square
of the average velocity, and since the temperature is a direct measure
of the avergae kinetic energy, guess what: a net force on the diaphragm
means a NET INSTANTANEOUS PRESSURE DIFFERENCE between the two sides.

What I think you are trying to say is that the piston is acted upon by the
energy of the sound wave in the *exact* same way as the air molecules. So,
how far does it move? The exact same distance as one molecule of air moves?

Depends upon how far the higher temperature side must move the diaphragm
such that it imparts enough energy on the other side such that it reaches
mechanical (and, indeed, euivalently) THERMAL equilibrium with it,

OR

it reaches mechanical equilibrium with whatever other force pooses its
motion.

The reality is that the piston does *not* act like an air molecule,

And, in a more precise fashion, there is no analysis of a single
molecule can lead to any clue about the propogation of sound.

need to look for a way to explain the vibration of the piston and contrast
that against the vibration of air molecules. It's that difference that
causes Doppler Distortion as I understand it.

Consider the following analytical tool: instead of a physical diaphragm,
look at the flow of energy past an arbitrary plane at right angles to
the flow of energy: can we consider the bulk proprties of the gas or
must we analyze each individual molecule as it interacts with this
plane? (hint, if you choose the latter, we'll all die before you
come back with an answer).

There's a LOT more lurking under here than you might imagine, but the
power of it is rather immense.

On Mon, 09 Aug 2004 11:25:54 +0100, Laurence Payne
wrote:

Here in the UK, we're ruled by a man who, 20 years ago, looked at
Cherie Booth across a crowded room and thought: "Now, there's a
good-looking woman!"

Worrying.


More likely he thought "You don't look at the mantelpiece when you're
poking the fire"

On Mon, 09 Aug 2004 13:43:01 +0100, Don Pearce
wrote:

On Mon, 09 Aug 2004 12:40:19 GMT, ow
(Goofball_star_dot_etal) wrote:

On Mon, 09 Aug 2004 08:03:09 +0100, Don Pearce
wrote:


OK, the definitive test has just occurred to me, and it is easy. Turn
the speaker through 90 degrees and make the test again. The motion of
the cone is now normal to the measuring axis and there can be no
doppler distortion. Anything that now remains is due to other effects.
What vanishes is possibly doppler.


An interesting idea but taken to its logical conclusion might suggest
that there would be no sound either. If the sound diffracts then the
path taken by the 4kHz has to bend and the path length will change as
the speaker moves at 50 Hz.

No - didn't understand any of that. Can you explain more fully?


I'm sure there must be some Law of Physics that says that at the
surface of the tweeter the velocity componet of souind is normal to
the surface or parallel to the motion of the surface. If not there
ought to be one! If this is the case then the direction of travel at
50Hz of the "tweeter" part of the speaker is the same as the
direction of the sound at 4kHz in exactly that region where the path
length is changing. The direction of the sound may change due to
diffraction (through ninety degrees, say) but by that time the doppler
deed is already done, I think. Anyhow there is little point in
speculating when we can measure.

"Randy Yates" wrote in message


An anechoic measurement would omit the reflected sources.

and if wishes for anechoic chambers were fishes...!!!!

This could be done in an anechoic room or using specialized measurements
like
time-delay spectrometry.

As Goofball points out, eleminate the reflections and you still have
refractions.

As I pointed out, the ideal piston has no radial radiation.

My literature search showed a JAES paper that attempted to correct for the
geometric issues related to cone-shaped diaphragms.

How do they get those polar response curves
of loudspeakers in the magazines (where vertical and horizontal
angular plots are usually shown separately)?

AFAIK, they use Anechoic chambers or TDS or something like it.

BTW, new, more complete test results are posted at
http://www.pcavtech.com/techtalk/doppler/ .

On Mon, 9 Aug 2004 13:21:05 -0400, "Arny Krueger"
wrote:

As I pointed out, the ideal piston has no radial radiation.

No - an ideal piston is one which moves as a single piece, and
possesses a full set of diffraction according to its geometry. That
will include radial radiation.

The ideal piston will have a polar response with a dispersion
inversely related to frequency.

A piston with no radial radiation would be completely unlike an ideal
piston.

d

Pearce Consulting
http://www.pearce.uk.com

"Don Pearce" wrote in message

On Mon, 9 Aug 2004 13:21:05 -0400, "Arny Krueger"
wrote:

As I pointed out, the ideal piston has no radial radiation.

No - an ideal piston is one which moves as a single piece, and
possesses a full set of diffraction according to its geometry. That
will include radial radiation.

The ideal piston will have a polar response with a dispersion
inversely related to frequency.

A piston with no radial radiation would be completely unlike an ideal
piston.

We obviously have different ideals.

;-)

On Sun, 8 Aug 2004 18:47:31 -0400, "Arny Krueger"
wrote:

"Goofball_star_dot_etal" wrote in message


I've got the radio if you get the urge to broadcast the raw data...

Sounds like an idea. I'm going to try to not pull an John Atkinson
hide-the-data trick on you. I didn't save the data from the two three-tone.
I'm going to do several tests in quick succession so that the acoustical
setup remains the same. I'll also try to do it when its acoustically quiet.


Well good data takes time, effort and money to get so I am not
surprised if anybody does not want to give it away so that somebody
else can steal the credit or criticize.

I'm not sure why you decided to trigger the JA alarm. . .

"Goofball_star_dot_etal" wrote in message

On Sun, 8 Aug 2004 18:47:31 -0400, "Arny Krueger"
wrote:

"Goofball_star_dot_etal" wrote in message


I've got the radio if you get the urge to broadcast the raw data...

Sounds like an idea. I'm going to try to not pull an John Atkinson
hide-the-data trick on you. I didn't save the data from the two
three-tone. I'm going to do several tests in quick succession so
that the acoustical setup remains the same. I'll also try to do it
when its acoustically quiet.

Well good data takes time,

I hope you find the 18 or so megabytes of new data posted at
http://www.pcavtech.com/techtalk/doppler/ to be at least good enough to be
interesting. ;-)

effort and money to get so I am not
surprised if anybody does not want to give it away so that somebody
else can steal the credit or criticize.

I surely wasn't surprized, when Atkinson balked. His justification was err,
unique. I think he saw the ground crumbling under his feet.

I'm not sure why you decided to trigger the JA alarm. . .

I think Atkinson needs to know that not everybody plays by his self-serving
rules. Some people just post the data, and let the chips fall where they
will. That's how I often learn interesting new stuff! ;-)

I don't think anyone intended that "superposition" be used
willie-nilly. How about an explanation of why a moving "tweeter"
does not produce doppler.

IM effects, of which doppler summation are a part IMO, are also dependant on
total piston excursion. Thus large diameter woofers suffer less from such
effect at low frequencies. Since cone excursion is reduced inversely with
increasing frequency, IM effects become progressively more negligable.
Arny's 2 different frequency suites seem to show this. Also a two tone test
suite is never free of FM affects because a complete higher frequency cycle
will always originate at different excursion locations within the excursion
pattern governed by the low frequency leading to the lower frequency
modulated phase shifting. Ideally one would want to use a non-harmonic or
randomized stimulus at a low frequency/high excursion and then measure the
effect on the higher signal.


Well, this is all very interesting but it does not address whether The
Pinciple of Linear Superposition is applicable to this case.


Perhaps, I don't understand what is specifically meant by linear vs.
non-linear superposition here. This thread is interesting. Please
Explain.

Don Pearce claims, in effect, to have THE LAWS OF PHYSICS and MATHS on
his side. However, he argues that (he wishes) there is no FM
therefore superposition proves that he is correct in his original wish
that the system is linear, so that superposition applies, and
therefore no FM occurs.


Wessel

I note that you did not take the hint (in the thread "Speaker
transient analysis") that I thought your statement:

"So yes,the acoustical output is directly proportional to the velocity
(not the force applied)" was incorrect.

Acoustic output is directly proportional to both, but your specific
reference to the acceleration in this matter is well noted as that is
what matters as it directly correlates with the acoustic output via
the equation below. The fact that piston acceleration is the link to
acoustic output here is due to the fact that the mechanical model of a
loudspeaker is based on the system being subject to a constant
velocity (movement0 and not a constant applied force.


Svante wrote:

p=U*rho0*w/(4*pi*r)

where U is the volume flow in m3/s (=surface*velocity), rho0=1.2kg/m3,
w is the angular frequency, and r is the distance.
After some thinking about this equation, one can realise that sound
pressure is roportional to the piston *acceleration* (comes from w*U,
ie derivative of the flow).

Nobody else seemed to notice that these two statements were different.
. .




So this is simple, stright-forward intermodulation between the two
tones.

d

Pearce Consulting
http://www.pearce.uk.com

On 9 Aug 2004 14:06:30 -0700, (Wessel Dirksen)
wrote:

I don't think anyone intended that "superposition" be used
willie-nilly. How about an explanation of why a moving "tweeter"
does not produce doppler.

IM effects, of which doppler summation are a part IMO, are also dependant on
total piston excursion. Thus large diameter woofers suffer less from such
effect at low frequencies. Since cone excursion is reduced inversely with
increasing frequency, IM effects become progressively more negligable.
Arny's 2 different frequency suites seem to show this. Also a two tone test
suite is never free of FM affects because a complete higher frequency cycle
will always originate at different excursion locations within the excursion
pattern governed by the low frequency leading to the lower frequency
modulated phase shifting. Ideally one would want to use a non-harmonic or
randomized stimulus at a low frequency/high excursion and then measure the
effect on the higher signal.


Well, this is all very interesting but it does not address whether The
Pinciple of Linear Superposition is applicable to this case.


Perhaps, I don't understand what is specifically meant by linear vs.
non-linear superposition here. This thread is interesting. Please
Explain.

If a system is linear you can add and "special arithmetic, O level" is
more than enough maths for the job. If a system is non-linear it
involves some multiplication in if you use the principle of linear
superposition you are "****ed". I don't know of "non-linear
superposition". In the case of doppler modulation, as far as I can
see, you modulate (multiply) the wavelength which is related to phase
and frequency. If the path length changes while the velocity of sound
remains constant then you modulate linear displacement, phase,
frequency etc. and linear superposition will not help you since it is
not applicable to multiplication. I am no expert in this, you will
note, but am quite welll endowed with common sense. (usually) I have a
slight problem with the fact that the air next to the cone is
stationary with respect to the cone, in the case in point, but my
common sense tells me that it will all come out in the wash ( to a
first approximation)- if the overall path length is changed, then you
will get doppler. I can confirm that I have measured it in Arnie's
data but I don't yet know whether it is the same magnitude as would be
calculated by a simple model of a tweeter moving in "free" space, (We
don't know the displacement of the voice coil.)


Don Pearce claims, in effect, to have THE LAWS OF PHYSICS and MATHS on
his side. However, he argues that (he wishes) there is no FM
therefore superposition proves that he is correct in his original wish
that the system is linear, so that superposition applies, and
therefore no FM occurs.


Wessel

I note that you did not take the hint (in the thread "Speaker
transient analysis") that I thought your statement:

"So yes,the acoustical output is directly proportional to the velocity
(not the force applied)" was incorrect.

Acoustic output is directly proportional to both, but your specific
reference to the acceleration in this matter is well noted as that is
what matters as it directly correlates with the acoustic output via
the equation below. The fact that piston acceleration is the link to
acoustic output here is due to the fact that the mechanical model of a
loudspeaker is based on the system being subject to a constant
velocity (movement0 and not a constant applied force.


Svante wrote:

p=U*rho0*w/(4*pi*r)

where U is the volume flow in m3/s (=surface*velocity), rho0=1.2kg/m3,
w is the angular frequency, and r is the distance.
After some thinking about this equation, one can realise that sound
pressure is roportional to the piston *acceleration* (comes from w*U,
ie derivative of the flow).

Nobody else seemed to notice that these two statements were different.
. .




So this is simple, stright-forward intermodulation between the two
tones.

d

Pearce Consulting
http://www.pearce.uk.com

On Mon, 9 Aug 2004 14:10:04 -0400, "Arny Krueger"
wrote:

I think Atkinson needs to know that not everybody plays by his self-serving
rules. Some people just post the data, and let the chips fall where they
will. That's how I often learn interesting new stuff! ;-)


You should consider whether the experiment is worth publishing
formally in a journal. I think it may be good enough if it has not
been published before. I have my name on plenty of papers but an audio
one might would be a first and so would actually writing one. . . If
you want to publish then it is time to shut up.

ow (Goofball_star_dot_etal) writes:
[...]
If a system is linear you can add and "special arithmetic, O level" is
more than enough maths for the job. If a system is non-linear it
involves some multiplication in if you use the principle of linear
superposition you are "****ed".

Wow, that's eloquent! Hey, any way you can get the idea across!

Actually the idea of superposition goes all the way out to abstract
mathematics. You can consider a "system" a mapping, call it f(.), from
one domain (the input), call it X, to another domain (the output),
call it Y. Thus Y = f(X). In abstract algebra, a mapping is
"homomorphic" if, for two inputs x1 and x2, f(x1 + x2) = f(x1) +
f(x2). Note that the operation "+" on the left side of the "=" is in
the domain X, while on the right side it is in the domain Y. A
"system" (in the engineering sense) obeys the superposition principle
if and only if the mapping corresponding to that system is
homomorphic. In other words, "homorphism" and "superposition" are the
same thing.
--
% Randy Yates % "My Shangri-la has gone away, fading like
%% Fuquay-Varina, NC % the Beatles on 'Hey Jude'"
%%% 919-577-9882 %
%%%% % 'Shangri-La', *A New World Record*, ELO
http://home.earthlink.net/~yatescr

Dick Pierce wrote:


WOW! What a neat f*cking idea! Analyzing sound based on the concepts
of the kinetic theory of gasses!

Dick, things work better here when we keep discussion at a
friendly level and recognize that all are not at the
technical depth that we have chosen to be.

From what you wrote, I get the impression that you agree
with my analysis. Is that correct or just wishfull
thinking? :-)


Bob
--

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

A. Einstein

On Mon, 9 Aug 2004 11:43:13 -0400, "Arny Krueger"
wrote:

"Arny Krueger" wrote in message


"Goofball_star_dot_etal" wrote in message


I've got the radio if you get the urge to broadcast the raw data...

Yes Goofball, you do have those specialized programs that look at the phase
of sidebands, right?

I think it must do so in order to demodulate but it can certainly tell
the difference between AM and FM.

Sounds like an idea. I'm going to try to not pull a John Atkinson
hide-the-data trick on you.

I collected the data at 16/44 to keep the data files a little shorter.


I'll have a go tonight.

I didn't save the data from the two three-tone tests.

But I did this time.


I'm not sure what I can do with three tones except maybe tune into one
or the other under the same conditions and see what changes.

I'm going to do several tests in quick succession so that
the acoustical setup remains the same.

OK, I redid the tests at 3 different levels, picked to be more
standard-like.

I just posted the revised graphic results and links to the raw test data
files at:

http://www.pcavtech.com/techtalk/doppler/

Enjoy!

Last time I used the program ( for your friend JA) I split it into two
parts. The first part demodulated and outputted a file. You can
have.these files of your data . It was either in speadsheet form or
wav which can be converted to text via CoolEdit and then plotted
using Excel. I can't remember which. The second part was a viewer
which did the FFTs and polar plots. I could not get hold of the terms
of the license so I must keep the software to myself at this stage.



I'll also try to do it when its acoustically quiet.

I wish.



It would be useful to have an estimate or crude measurement of the
cone excursion so that people have a chance to calculate or speculate
first so that they can place their bets before the race is run. . .

On Tue, 10 Aug 2004 02:39:51 GMT, Randy Yates wrote:


Wow, that's eloquent! Hey, any way you can get the idea across!

Actually the idea of superposition goes all the way out to abstract
mathematics. You can consider a "system" a mapping, call it f(.), from
one domain (the input), call it X, to another domain (the output),
call it Y. Thus Y = f(X). In abstract algebra, a mapping is
"homomorphic" if, for two inputs x1 and x2, f(x1 + x2) = f(x1) +
f(x2). Note that the operation "+" on the left side of the "=" is in
the domain X, while on the right side it is in the domain Y. A
"system" (in the engineering sense) obeys the superposition principle
if and only if the mapping corresponding to that system is
homomorphic. In other words, "homorphism" and "superposition" are the
same thing.
--

So I take it that you are not a fan of plain english. . .

"Goofball_star_dot_etal" wrote in message

On Tue, 10 Aug 2004 02:39:51 GMT, Randy Yates wrote:


Wow, that's eloquent! Hey, any way you can get the idea across!

Actually the idea of superposition goes all the way out to abstract
mathematics. You can consider a "system" a mapping, call it f(.),
from one domain (the input), call it X, to another domain (the
output), call it Y. Thus Y = f(X). In abstract algebra, a mapping is
"homomorphic" if, for two inputs x1 and x2, f(x1 + x2) = f(x1) +
f(x2). Note that the operation "+" on the left side of the "=" is in
the domain X, while on the right side it is in the domain Y. A
"system" (in the engineering sense) obeys the superposition principle
if and only if the mapping corresponding to that system is
homomorphic. In other words, "homorphism" and "superposition" are the
same thing.
--

So I take it that you are not a fan of plain english. . .

I guess he's trying to keep up with those who are not fans of train
whistles. ;-)

"Goofball_star_dot_etal" wrote in message

On Mon, 9 Aug 2004 11:43:13 -0400, "Arny Krueger"
wrote:

"Arny Krueger" wrote in message


"Goofball_star_dot_etal" wrote in message


I've got the radio if you get the urge to broadcast the raw data...

Yes Goofball, you do have those specialized programs that look at
the phase of sidebands, right?

I think it must do so in order to demodulate but it can certainly tell
the difference between AM and FM.

That's the key.

I'm not sure what I can do with three tones except maybe tune into one
or the other under the same conditions and see what changes.

Tuning into the two upper tones seems to be of the essence.

I just posted the revised graphic results and links to the raw test
data files at:

http://www.pcavtech.com/techtalk/doppler/

Last time I used the program ( for your friend JA) I split it into two
parts. The first part demodulated and outputted a file. You can
have.these files of your data .

I would love to have them.

It was either in speadsheet form or
wav which can be converted to text via CoolEdit and then plotted
using Excel. I can't remember which.

I have both, no sweat.

The second part was a viewer
which did the FFTs and polar plots. I could not get hold of the terms
of the license so I must keep the software to myself at this stage.

How about graphic files representing the output of the program?


It would be useful to have an estimate or crude measurement of the
cone excursion so that people have a chance to calculate or speculate
first so that they can place their bets before the race is run. . .

The cone excursion is sufficiently small that I can't accurately
characterize it. I just did a run at +20 ( 10 vrms applied to the voice
coil) hoping that I would have some sort of an idea - maybe 1/8" or less.
BTW, the data has been uploaded.

BTW, my proper email address is arnyk, at my isp's domain which is
comcast.net.

ow (Goofball_star_dot_etal) writes:

On Tue, 10 Aug 2004 02:39:51 GMT, Randy Yates wrote:


Wow, that's eloquent! Hey, any way you can get the idea across!

Actually the idea of superposition goes all the way out to abstract
mathematics. You can consider a "system" a mapping, call it f(.), from
one domain (the input), call it X, to another domain (the output),
call it Y. Thus Y = f(X). In abstract algebra, a mapping is
"homomorphic" if, for two inputs x1 and x2, f(x1 + x2) = f(x1) +
f(x2). Note that the operation "+" on the left side of the "=" is in
the domain X, while on the right side it is in the domain Y. A
"system" (in the engineering sense) obeys the superposition principle
if and only if the mapping corresponding to that system is
homomorphic. In other words, "homorphism" and "superposition" are the
same thing.
--

So I take it that you are not a fan of plain english. . .

If the concepts involved were just a matter of "plain english" then it
probably wouldn't have taken mathematicians, physicists, and engineers
centuries to formalize them.

Also, I have found that, while intuition (which is what I call the
level of explanation you were attempting) can be helpful at certain
stages of understanding, over-relying on it can lead to errors in
analysis. It is necessary, if you want to do more than blow smoke in
front of mirrors, to formally derive the results one is asserting.
--
Randy Yates
Sony Ericsson Mobile Communications
Research Triangle Park, NC, USA
, 919-472-1124

On 10 Aug 2004 10:19:38 -0400, Randy Yates
wrote:

(Goofball_star_dot_etal) writes:

On Tue, 10 Aug 2004 02:39:51 GMT, Randy Yates wrote:


Wow, that's eloquent! Hey, any way you can get the idea across!

Actually the idea of superposition goes all the way out to abstract
mathematics. You can consider a "system" a mapping, call it f(.), from
one domain (the input), call it X, to another domain (the output),
call it Y. Thus Y = f(X). In abstract algebra, a mapping is
"homomorphic" if, for two inputs x1 and x2, f(x1 + x2) = f(x1) +
f(x2). Note that the operation "+" on the left side of the "=" is in
the domain X, while on the right side it is in the domain Y. A
"system" (in the engineering sense) obeys the superposition principle
if and only if the mapping corresponding to that system is
homomorphic. In other words, "homorphism" and "superposition" are the
same thing.
--

So I take it that you are not a fan of plain english. . .

If the concepts involved were just a matter of "plain english" then it
probably wouldn't have taken mathematicians, physicists, and engineers
centuries to formalize them.


I always thought they were slow.. .

Also, I have found that, while intuition (which is what I call the
level of explanation you were attempting) can be helpful at certain
stages of understanding, over-relying on it can lead to errors in
analysis.

Agreed but lean about intuition:
http://www.amazon.co.uk/exec/obidos/...293460-4259040


:It is necessary, if you want to do more than blow smoke in
front of mirrors, to formally derive the results one is asserting.
--

Feel free to imply that I am an uncouth blowhard.

I've done the analysis, calculations and analysed the experimental
results, spotted some circular arguments and other errors. It ain't
"rocket science" but where were you during this time with your faultly
BS detector? I want some numbers from you now.

On Tue, 10 Aug 2004 08:38:27 -0400, "Arny Krueger"
wrote:

"Goofball_star_dot_etal" wrote in message

On Mon, 9 Aug 2004 11:43:13 -0400, "Arny Krueger"
wrote:

"Arny Krueger" wrote in message


"Goofball_star_dot_etal" wrote in message


I've got the radio if you get the urge to broadcast the raw data...

Yes Goofball, you do have those specialized programs that look at
the phase of sidebands, right?

I think it must do so in order to demodulate but it can certainly tell
the difference between AM and FM.

That's the key.

I'm not sure what I can do with three tones except maybe tune into one
or the other under the same conditions and see what changes.

Tuning into the two upper tones seems to be of the essence.

I just posted the revised graphic results and links to the raw test
data files at:

http://www.pcavtech.com/techtalk/doppler/

Last time I used the program ( for your friend JA) I split it into two
parts. The first part demodulated and outputted a file. You can
have.these files of your data .

I would love to have them.


They won't be long coming. The output files are ascii speadsheet , the
sampling is decimated /20 so if you feed it to CoolEdit, tell it it is
sampled at 22050 and drop a zero of the frequency scale. The numbers
are generally 1 so need to be read into floating point format and
amplified by a few tens of k to be visible.

The 4025 Hz at 0, +10, +20dB is clean enough without averaging but
the rest needs further processing to improve the signal to noise,
which I have not done yet. The sample I sent you shows more than a
hundred revs at 50Hz on top of eachother.

It was either in speadsheet form or
wav which can be converted to text via CoolEdit and then plotted
using Excel. I can't remember which.

I have both, no sweat.

The second part was a viewer
which did the FFTs and polar plots. I could not get hold of the terms
of the license so I must keep the software to myself at this stage.

How about graphic files representing the output of the program?

Sure. Private or public?


It would be useful to have an estimate or crude measurement of the
cone excursion so that people have a chance to calculate or speculate
first so that they can place their bets before the race is run. . .

The cone excursion is sufficiently small that I can't accurately
characterize it. I just did a run at +20 ( 10 vrms applied to the voice
coil) hoping that I would have some sort of an idea - maybe 1/8" or less.
BTW, the data has been uploaded.


If that was 1/8" total, not +/- 1/8 you would make an old man very
happy!

BTW, my proper email address is arnyk, at my isp's domain which is
comcast.net.

I took your web site at its word. . .

"Goofball_star_dot_etal" wrote in message


On Tue, 10 Aug 2004 08:38:27 -0400, "Arny Krueger"
wrote:

"Goofball_star_dot_etal" wrote in message



Last time I used the program ( for your friend JA) I split it into
two parts. The first part demodulated and outputted a file. You can
have.these files of your data .

I would love to have them.


They won't be long coming. The output files are ascii speadsheet , the
sampling is decimated /20 so if you feed it to CoolEdit, tell it it is
sampled at 22050 and drop a zero of the frequency scale. The numbers
are generally 1 so need to be read into floating point format and
amplified by a few tens of k to be visible.

The 4025 Hz at 0, +10, +20dB is clean enough without averaging but
the rest needs further processing to improve the signal to noise,
which I have not done yet. The sample I sent you shows more than a
hundred revs at 50Hz on top of eachother.

What does it mean?

The second part was a viewer
which did the FFTs and polar plots. I could not get hold of the
terms of the license so I must keep the software to myself at this
stage.

How about graphic files representing the output of the program?

Sure. Private or public?

Private for now.

It would be useful to have an estimate or crude measurement of the
cone excursion so that people have a chance to calculate or
speculate first so that they can place their bets before the race
is run. . .

The cone excursion is sufficiently small that I can't accurately
characterize it. I just did a run at +20 ( 10 vrms applied to the
voice coil) hoping that I would have some sort of an idea - maybe
1/8" or less. BTW, the data has been uploaded.

If that was 1/8" total, not +/- 1/8 you would make an old man very
happy!

Be happy, I was thinking 1/8" total.

On Tue, 10 Aug 2004 14:17:57 -0400, "Arny Krueger"
wrote:

"Goofball_star_dot_etal" wrote in message


On Tue, 10 Aug 2004 08:38:27 -0400, "Arny Krueger"
wrote:

"Goofball_star_dot_etal" wrote in message



Last time I used the program ( for your friend JA) I split it into
two parts. The first part demodulated and outputted a file. You can
have.these files of your data .

I would love to have them.


They won't be long coming. The output files are ascii speadsheet , the
sampling is decimated /20 so if you feed it to CoolEdit, tell it it is
sampled at 22050 and drop a zero of the frequency scale. The numbers
are generally 1 so need to be read into floating point format and
amplified by a few tens of k to be visible.

The 4025 Hz at 0, +10, +20dB is clean enough without averaging but
the rest needs further processing to improve the signal to noise,
which I have not done yet. The sample I sent you shows more than a
hundred revs at 50Hz on top of eachother.

What does it mean?


Much the same as the LP stuff.Frequency ("4025 carrier") is the
radial component. Theta (degrees) is the angle, 360 degrees represents
one cycle at 50Hz. As I said it goes round many times and any
(asyncronous) noise would blur it The frequency scale is the reference
frequency, in this case exactly 4025 Hz plus the frequency deviation
at any point in the 50Hz cycle. It looks vaguely circular but in fact
it is not. It is like a cam so that if the modulation is a pure sine
wave at 50Hz the radius is a sine wave v angle. I rather like the case
where I set the minimum to 4025 Hz and the negative part "folds back"
to form two circles, for a pure sine wave. (not shown yet). A similar
plot of amplitude shows an approximate 90 degree shift wrt the
frequency plot. (not shown yet) The starting point is an arbitary
phase which depends upon when the recording was started during a 50Hz
cycle, so that data taken at different times have their maximum
deviations at different angular positions (with the present program)

The second part was a viewer
which did the FFTs and polar plots. I could not get hold of the
terms of the license so I must keep the software to myself at this
stage.

How about graphic files representing the output of the program?

Sure. Private or public?

Private for now.

Fine.

It would be useful to have an estimate or crude measurement of the
cone excursion so that people have a chance to calculate or
speculate first so that they can place their bets before the race
is run. . .

The cone excursion is sufficiently small that I can't accurately
characterize it. I just did a run at +20 ( 10 vrms applied to the
voice coil) hoping that I would have some sort of an idea - maybe
1/8" or less. BTW, the data has been uploaded.

If that was 1/8" total, not +/- 1/8 you would make an old man very
happy!

Be happy, I was thinking 1/8" total.


Well s**t, (plain english, note) the agreement between my simple-simon
model and experiment is about 20%.. I should worry about blowing
smoke!