Randy Yates wrote:

Bob Cain writes:

[...]

Why
WOULDN'T a speaker act as a moving platform?

I've given numerous physical reasons the behavior you expect can't and
won't happen [...]


1) It is not the behavior I "expect" - it is the behavior predicted by
a well-known physical law.

And that basic physical law is?


2) State your reason here and now - give it your best shot. Or else drop it.

I've done so many times in this and related threads in very
simple terms and I am frankly tired of writing it and
receiving not one attempt at a refutation. You've seen it
and had no comment.

The most recent thing that came to me as a consequence of
what I have presented is that it seems sort of silly that
the piston velocity which is responsible for the creation of
the wave is simultaneously responsible for distorting it.
Something is being counted twice here. In one sense it
makes it "this" from very simple physical relationships and
in another, because it exists, it makes it "something else?"

It is not necessasary to look at anything but the
instantaneous value of the piston velocity relative to the
medium to determine a pressure/velocity value that
propegates unchanged, except for some minor dissipative
losses, in the subsequent acoustic wave so how does it
matter what comes before or after it or what is mixed to get
it?

Find the falacy in the last paragraph, prove "Doppler
distortion" for arbitrary signals with a scientifically
acceptable derivation from first principles or drop it.


Bob
--

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

A. Einstein

William Sommerwerck wrote:



Do it yourself, Bob. This is trivial, high-school algebra. It does not require
fancy math of any sort.

The way you learn things -- that is, understand them -- is by doing them.

You still don't get it. I can't write a derivation of
something that I can show doesn't exist. Jeez.

If you think you can, then have at it.


Bob
--

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

A. Einstein

Bob Cain wrote:


It is not necessasary to look at anything but the instantaneous value of
the piston velocity relative to the medium to determine a
pressure/velocity value that propegates unchanged, except for some minor
dissipative losses, in the subsequent acoustic wave so how does it
matter what comes before or after it or what is mixed to get it?

Sorry, further qualification. As simply as that was stated,
it is true only with a piston in a tube. I haven't heard
anyone say, however, that that simplified situation won't
Dopple.


Bob
--

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

A. Einstein

Arny Krueger wrote:


You said post an expression, not lay out the detailed theory. If you can't
keep your stories straight, there's no need for me to honor your requests in
the future.

Let me try again. Please show me an expression for the
pressure/velocity of an acoustic wave as a function of
piston velocity which inorporates what is neccesasary to
quantitatively predict the "Doppler distortion" of an
arbitrary signal. I don't care if it has a closed form, if
is integro-differential or whatever.

If it does have a closed form algebraic solution for the two
tone case it would be especially useful.


Bob
--

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

A. Einstein

"Jim Carr"
"Phil Allison"

** We are all the victims of a pathetic NG troll's wet dream and a
hoax.

I think you have anger issues.



** I think you are a utter imbecile.


Bob Cain has no interest in the facts - he is having a giant hoot at
our expense.


Hardly.


** Pompous idiot's remark.


Bob is a good guy searching for an answer he can't determine
himself. He cannot prove a negative, so absent a mathematical proof
otherwise, he is free to deny its existence.


** Fool's logic - because he does not know how wrong he is not enough to
presume he is right.



Bob can correct me here, but from where I sit, Bob does not deny the
Doppler
shift. He completely accepts the formula fo = fs . (v - vo) / (v - vs).
What
he does not accept is that you can insert the speaker diaphragm's movement
as vs.


** Then he has a mental disability.

Like dyslexia or dyscalculia.


But here's the kicker: Either the above formula is wrong, there is no
Doppler Distortion, or somebody left out an assumption somewhere. Why?
Because the formula does not take into consideration the movement of the
diaphragm.


** That is your error.


The Doppler formula ignores the movement of the source AS IT CREATES THE
WAVES.


** That is just what the Doppler formula is all about in fact.



So, Bob's position is quite simple: Show a formula that will predict what
the Doppler shift will be based on the movement of the source itself when
creating the wave,


** The usual formula applies.


then perform an experiment that shows those results.


** Done that and posted all the details here too.

Not one scrap of use to someone with zero electronics knowledge.



So, it's easy to find the formula that shows how Doppler works (train
example) without taking into consideration the movement of the plane of
the
source that is creating the sound.


** You make the same error again.


I've seen numerous sites talk about
Doppler Distortion, but I've yet to uncover one that shows the actual
mathematical representation.


** I posted it a few day ago - but Bob the Troll has ignored it .


Somebody post this formula so we can all go to bed.


** See above.




............ Phil

Jim Carr wrote:


Bob can correct me here, but from where I sit, Bob does not deny the Doppler
shift. He completely accepts the formula fo = fs . (v - vo) / (v - vs). What
he does not accept is that you can insert the speaker diaphragm's movement
as vs. He accepts that you can put the speaker on the train and predict the
Doppler shift with the above formula as does everyone he's arguing with.

Exactly. That's why I've not entered any sub-discussion
about trains and whistles.


But here's the kicker: Either the above formula is wrong, there is no
Doppler Distortion, or somebody left out an assumption somewhere. Why?
Because the formula does not take into consideration the movement of the
diaphragm.

More specifically it only addresses the case of a velocity
that is constant in time. When it is not, the generation of
waves supplants the Doppler shift.

So, Bob's position is quite simple: Show a formula that will predict what
the Doppler shift will be based on the movement of the source itself when
creating the wave, then perform an experiment that shows those results. I'm
thinking he'd settle for the former.

Yes, exactly.


So, it's easy to find the formula that shows how Doppler works (train
example) without taking into consideration the movement of the plane of the
source that is creating the sound. I've seen numerous sites talk about
Doppler Distortion, but I've yet to uncover one that shows the actual
mathematical representation.

It's easy in the case of constant motion because that motion
is not part of any wave generation. Any motion that is
responsible for wave generation will incorporate the motion
into that process and do so linearly.


Somebody post this formula so we can all go to bed.

Really.

Honest, guys, I have no history of jousting windmills or
pursuing crank theories in my 40 some professional years.
If that's what is happening this time it will be a first and
perhaps a sign that something bad is happening. I am really
quite certain, however, that that isn't the case. The ducks
just line up too well and I don't see another line of ducks
standing to shoot at.

I do have some long standing disagreements in comp.dsp on
interpretation of the DFT and its place in the world of
real, physical signals, which blossoms now and again, but
this isn't a matter of intepretations which don't affect
results, but a physical phenomenon that either does in some
derivable way or doesn't at all.


Bob
--

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

A. Einstein

Bob Cain writes:

Randy Yates wrote:

Bob Cain writes:

[...]

Why
WOULDN'T a speaker act as a moving platform?

I've given numerous physical reasons the behavior you expect can't and
won't happen [...]
1) It is not the behavior I "expect" - it is the behavior predicted
by
a well-known physical law.

And that basic physical law is?

2) State your reason here and now - give it your best shot. Or else
drop it.

I've done so many times [...]

So it's dropped.
--
% Randy Yates % "Remember the good old 1980's, when
%% Fuquay-Varina, NC % things were so uncomplicated?"
%%% 919-577-9882 % 'Ticket To The Moon'
%%%% % *Time*, Electric Light Orchestra
http://home.earthlink.net/~yatescr

On Tue, 17 Aug 2004 20:09:12 -0700, "Jim Carr"
wrote:

Bob can correct me here, but from where I sit, Bob does not deny the Doppler
shift. He completely accepts the formula fo = fs . (v - vo) / (v - vs). What
he does not accept is that you can insert the speaker diaphragm's movement
as vs. He accepts that you can put the speaker on the train and predict the
Doppler shift with the above formula as does everyone he's arguing with.

...

So, it's easy to find the formula that shows how Doppler works (train
example) without taking into consideration the movement of the plane of the
source that is creating the sound. I've seen numerous sites talk about
Doppler Distortion, but I've yet to uncover one that shows the actual
mathematical representation.

Somebody post this formula so we can all go to bed.

I think that would be fo = fs . (v - vo) / (v - vs).

Good night.



Only complete fools keep going when they are being conned.

Like I said...

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

In alt.music.home-studio,rec.audio.tech,rec.audio.pro, Bob Cain
wrote:



William Sommerwerck wrote:



Do it yourself, Bob. This is trivial, high-school algebra. It does not require
fancy math of any sort.

The way you learn things -- that is, understand them -- is by doing them.

You still don't get it. I can't write a derivation of
something that I can show doesn't exist. Jeez.

Pretend that the cone is, at every instant, the source of sound.
Write the equation/transfer function based on the idea that the time
for a signal generated by the speaker to be picked up by a mic depends
on the distance between the cone (whose position varies) and the mic
at every instant.

If you think you can, then have at it.

Or just put the driver on a shaker table as I and others have
mentioned before. Don't even connect up the driver, just drive the
shaker table with the algebraic sum of 50 Hz and 1kHz sinewaves.

Bob

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

Jim Carr wrote:

"Mark" wrote in message
om...


Using 344.3 m/sec for the speed of sound and the Doppler equations
found he

http://www.mathpages.com/rr/s2-04/2-04.htm


Help this poor uneducated soul, will ya? The formula you are referencing
states that if the source is at rest, there is no apparent frequency shift.
It is inherently impossible for the source to be at rest *and* create a
sound wave. After all, sound waves are compression waves, right?

They mean that the source's average position is at rest.
That whole discussion is a static analysis with fixed
velocities. Dynamics are a different animal.

Note that the article mentions nothing about the "dynamic
Doppler shift" induced by the source on itself in the
process of producing acoustic waves. Odd, that. :-)


Bob
--

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

A. Einstein

"Jim Carr" writes:

"Mark" wrote in message
om...

Using 344.3 m/sec for the speed of sound and the Doppler equations
found he

http://www.mathpages.com/rr/s2-04/2-04.htm

Help this poor uneducated soul, will ya? The formula you are referencing
states that if the source is at rest, there is no apparent frequency shift.

Jim,

No, that is not correct, in general. If u = 0 AND v = 0, then there is no
Doppler shift. If u = 0 but v != 0, then there will be a shift.

It is inherently impossible for the source to be at rest *and* create a
sound wave.

Not the way the system is defined. The source reference frame is defined to be the
reference frame which the motion of the source oscillation is relative to. For
example, if the source oscillation's position as a function of time is
given as x(t) = A*cos(w*t + phi), then the reference frame in which this
"x(t)" is specified is the source reference frame. It is the velocity
of that reference frame relative to the observer's reference frame that
is relevent.

And before you go "Aha! Then there is no Doppler-modulating motion for
a two-tone system" let me respond that all we have to do is make the
reference frame the one which the *specific* oscillation corresponding
to the high-frequency oscillation is relative to.
--
% 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

Randy Yates wrote:

So it's dropped.

Randy, if you are going to be so nasty, the least you could
do is refute what I've said. Let me get something out of it
anyway.


Bob
--

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

A. Einstein

"Bob Cain"


Randy, if you are going to be so nasty, the least you could
do is refute what I've said. Let me get something out of it
anyway.



** Your meaningless drivel has no refutation.





......... Phil

Bob Cain writes:

Randy Yates wrote:

So it's dropped.

Randy, if you are going to be so nasty, the least you could do is
refute what I've said. Let me get something out of it anyway.

How can I refute what you have refused to clearly restate?
--
% Randy Yates % "Though you ride on the wheels of tomorrow,
%% Fuquay-Varina, NC % you still wander the fields of your
%%% 919-577-9882 % sorrow."
%%%% % '21st Century Man', *Time*, ELO
http://home.earthlink.net/~yatescr

"Ben Bradley" wrote in message
...

So, it's easy to find the formula that shows how Doppler works (train
example) without taking into consideration the movement of the plane of
the
source that is creating the sound. I've seen numerous sites talk about
Doppler Distortion, but I've yet to uncover one that shows the actual
mathematical representation.

Somebody post this formula so we can all go to bed.

I think that would be fo = fs . (v - vo) / (v - vs).

This uneducated rube thinks you're wrong. Assume vo is zero. The source, a
speaker, is producing a pure 50Hz signal and nothing else. It's stationary.
I don't hear the Doppler effect, right? But according to you, I must take
into account the velocity of the diaphragm creating the sound. That means I
*will* hear the Doppler effect (or at least I could measure it). .

It just doesn't make sense to me. The diaphragm is creating waves at the
exact same point each cycle - compress-rarefy, compress-rarefy. It happens
50 times per second. The wavelength remains unchanged. So where is the
Doppler shift?

They way I've seen Doppler distortion explained is that higher frequencies
are "riding" on the lower (or lowest, I don't know) frequency and it is
*that* movement which creates the Doppler effect. Obviously your formula
doesn't take that into account.

Granted, I used to think algebra was the plural form of algae, but I'm
pretty sure I understand the basic Doppler formual enough to know it doesn't
factor in the movement of the source as it creates the wave.

"Randy Yates" wrote in message
...

No, that is not correct, in general. If u = 0 AND v = 0, then there is no
Doppler shift. If u = 0 but v != 0, then there will be a shift.

It is inherently impossible for the source to be at rest *and* create a
sound wave.

Not the way the system is defined.

My initial reaction is, "That's cheating!" It is impossible to create a
sound without movement, so why are you allowed to say there is? What am I
missing?

The source reference frame is defined to be the
reference frame which the motion of the source oscillation is relative to.
For
example, if the source oscillation's position as a function of time is
given as x(t) = A*cos(w*t + phi), then the reference frame in which this
"x(t)" is specified is the source reference frame. It is the velocity
of that reference frame relative to the observer's reference frame that
is relevent.

And before you go "Aha! Then there is no Doppler-modulating motion for
a two-tone system" let me respond that all we have to do is make the
reference frame the one which the *specific* oscillation corresponding
to the high-frequency oscillation is relative to.

Okay, I figure t=time. The rest of the variables I don't know. Like I said
before, I have no training in this field, so help me out.

Or maybe you can just point me to a formula the predicts the Doppler Effect
in a two-tone system. I see the formula you referenced as predicting a
single tone source moving in relation to the observer. If the source is
"stationary" there is no Doppler, right?

So, there has gotta be a formula where I plug in frequency1, frequency2, and
the velocity of diaphragm resulting in frequency1 remaining unchanged and
frequency2 being altered in some way, right?

Please don't tell me to figure it out myself. I develop billing and
accounting software for law firms. The most complicated math I've had to do
in the last five years is calculate the amount of interest based on the
number of days a bill is past due. It's been a long time since I've done
anything even remotely complex.

Randy Yates wrote:

Bob Cain writes:


Randy Yates wrote:


So it's dropped.

Randy, if you are going to be so nasty, the least you could do is
refute what I've said. Let me get something out of it anyway.


How can I refute what you have refused to clearly restate?

All right, I'll accept that you haven't read the thread.

I've found a new way to state it anyway, that I think makes
it clearer.

I'm saying that the instantaneous velocity of the piston is
transfered to the wave in the right position, since it is
moving in step with it, to propegate that velocity out as an
acoustic wave. It is _in_ the acoustic wave it is creating
and it is at the right place at all times to impart the
correct velocity _because_ it is in it.

It doesn't matter what signals might have been mixed
upstream to get the signal that controls the velocity of
that piston. It will be moving in lock step with the wave
defined by that signal and will always be in the right place
to deliver the right velocity to the outgoing wave.

If, on the other hand the piston is moving with a constant
velocity superimposed on the signal velocity, it has no way
to transfer that constant velocity to the air because
contant velocity doesn't create a wave. At f=0 it runs out
of punch. It ceases abruptly to transduce at all. In that
case, the piston will always be in the wrong position to
correctly impart the desired velocity signal and that error
is Doppler shift.

If the above is truly crazy, then I'll agree that I'm over
the edge. But I don't think so. What, exactly, is wrong
with it?

I don't want to talk about trains and whistles.


Bob
--

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

A. Einstein

"ruffrecords" wrote in message
...


Looks to me like Porky has moved up a few grades and phil is the new
class idiot. (and I don't know if I can walk and chew gum because I hate
the stuff).

Ian

Thanks! (I think) *LOL*

"William Sommerwerck" wrote in message
...
I don't give a rat's ass about opinion. Show me the science
reduced as it must be to an expression which predicts the
consequences on any waveform and which can be exprimentally
verified.

I'm not being snide when I ask, why don't you work it out for yourself?
It's not
horribly complex.

All you need is to apply the formula for the Doppler shift of sound to the
low-frequency excursions of the cone.

You are still using the train/whistle model and it doesn't apply. The
speaker cone is NOT actually producing the sound, there is a conversion
taking place in the air, converting the low velocity molecular motion of the
air moved by the cone into a high velocity wave which propagates away from
the source. In other words, the speaker moves the air and the air produces
the actual sound wave. This has been known for more than fifty years, in
fact, it may go back as far as 1877 to Lord Rayleigh's "Theory of Sound".
Item 12 in the following link would seem to have at least some relevance
since a siren is a more apt model that the train/whistle. Basically, as I
understand it when two (or more) tones are produced from the same complex
sound source they have no effect on each other's frequencies.
http://www.measure.demon.co.uk/docs/Theory.html
How come you folks can't see that the train/whistle model is something
totally different from a loudspeaker (or other single source) producing a
complex waveform? There is no such thing as a "HF tone riding on an LF tone"
coming from a loudspeaker, there is just a single complex waveform being
generated. In any event, the source of the sound isn't the speaker cone
(which is just supplying the mechanical energy and exciting the molecules in
the air), it's the air transforming the mechanical energy into acoustical
energy. A horn speaker is more efficient that a direct radiator simply
because it is more efficient in converting the mechanical energy of the cone
into acoustical energy, in short, it's an acoustical impedence transformer.
Conversely, if the horn is a more efficient transformer, the direct radiator
is simply a less efficient version of the same thing, the point being that
it is ultimately the air converting the mechanical energy into acoustical
energy.
Actually, it seems so simple to me, that I just might be wrong! Who am I
to argue with a bunch of folks who obviously have more education on the
subject than I do? (And that isn't a snide remark, it's the truth.) Could it
be that my lesser education doesn't give me preconceived notions that keep
getting in the way? In any event, I can find no flaw in the above logic,
though the flaw is obvious and fundamental (and fatal!) in the train/whistle
model as applied to loudspeakers.
I think this may be one of those cases where the "obvious" assumption is
wrong because it looks so obvious on the surface that no one bothers to look
deeper and admit to the fundamental flaw. The train/whistle model is so
simple and so elegant that no one bothers to question whether it applies in
this case.

"Ben Bradley" wrote in message
...
In alt.music.home-studio,rec.audio.tech,rec.audio.pro, Bob Cain
wrote:



William Sommerwerck wrote:



Do it yourself, Bob. This is trivial, high-school algebra. It does not
require
fancy math of any sort.

The way you learn things -- that is, understand them -- is by doing
them.

You still don't get it. I can't write a derivation of
something that I can show doesn't exist. Jeez.

Pretend that the cone is, at every instant, the source of sound.
Write the equation/transfer function based on the idea that the time
for a signal generated by the speaker to be picked up by a mic depends
on the distance between the cone (whose position varies) and the mic
at every instant.

If you think you can, then have at it.

Or just put the driver on a shaker table as I and others have
mentioned before. Don't even connect up the driver, just drive the
shaker table with the algebraic sum of 50 Hz and 1kHz sinewaves.


If you do that, you don't need the driver, the shaker table becomes the
"speaker", and there will be no Doppler distortion for the exact same reason
there is no Doppler distortion from the speaker. However, if you drove the
table with the 50Hz signal and the speaker with 1KHz, you would get Doppler
distortion because the train/whistle model would then fit perfectly.

"Arny Krueger" wrote in message
...
"Porky" wrote in message


:-) Yep, I just had an attack of common sense before I started
posting again. I decided to try to contribute positively to the group
and to forget about any preconceived notions I may have had about
group members. It seems that after doing so, my opinions of many of
you went up quite a bit, which means that it was my misconceptions
that were the problem. I apologize to all for that.



Wow! This close to being a first in the history of Usenet. I'm sure it has
happened before, but I can't say where or when.

Good stuff!

Thanks Arny, my intentions were good from the first, but I got off on the
wrong foot and couldn't get straightened out. I finally realized that I was
behaving like a troll, even though that wasn't my intention. I hope that
from now on we can disagree in an agreeable manner, and perhaps even agree
occasionally.:-) Not on this one though, I started off willing to agree that
Doppler distortion in speakers could occur, until Bob's comments made me
realize that I was using the train/whistle as the basis for my opinion and
that it didn't apply to loudspeakers. Unfortunately I haven't the math and
physics education to adequately express what now seems so obvious to me. If
you'll totally forget the train/whistle thing and the "HF tone riding on a
LF tone" thing and start from scratch, I think you'll see what Bob and I
see. Remember two things, an oscilloscope pattern is at best a two
dimensional representation of a three dimensional occurance and doesn't
necessarily represent what is actually happening, and the speaker cone
doesn't actually generate the sound wave (velocity too low and p-p cone
travel too short for the wavelength), the air it moves does.

"Arny Krueger" wrote in message
news
"Porky" wrote in message


"Randy Yates" wrote in message
...

Bob Cain writes:

ruffrecords wrote:

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

Exactly,

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

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

I think you've contrdicted yourself. A whistle riding on a train would be
an
example of a linear system if the motion of the train does not change the
operational parameters of the whistle.

Both sounds are being produced
simultaneously by the complex electrical waveform driving the speaker
cone which moves in accordance. Assuming that the speaker is being
driven within its linear limits, the cone's motion accurately follows
the driving signal, and it is a linear system.

So far so good.

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

But it is. A speaker generating a acostical signal that is received with
Doppler distoriton is just as linear as that train whistle, and the
Doppler
distortion in either case has a common cause. This common cause is the
relative motion of the source and the receiver.

Only if you accept that there is a high frequency tone "riding on" a low
frequency tone. That is the case with the train/whistle, but it isn't with
the speaker which is producing the two tones in combination as a single
complex waveform.

"William Sommerwerck" wrote in message
...
Since I can set the speaker's position however I like by setting the
DC bias, it follows that I can change that position while the high
frequency sound is playing back on top of it. I could move it at say,
1 ft per second -- this speed is far too slow to produce a sound, and
is practically DC. If you agree that I can set the position of the
sound source by adjusting the DC bias, then it follows that I can
*change* the position of the sound source by *changing* the DC bias.
Any change in the position of the sound source is movement of the
sound source (by the definitions of "movement" and "position"), and
any movement of the sound source creates doppler distortion. QED.

This is basically correct reasoning.

But it applies only if one accepts that the speaker is directly producing
the soundwave, and it is NOT, it merely supplies the mechanical energy that
allows the air to convert it to acoustical energy!

"Bob Cain" wrote in message
...


Arny Krueger wrote:

"Bob Cain" wrote in message


Randy Yates wrote:


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

Randy has spoken. Without one shread of a predictive
theory. Odd, that.


GMAB. He cited Halliday and Resnick. I cited the JAES. Someone else
cited
the JAES.

BTW Halliday and Resnick ride on:


http://jws-edcv.wiley.com/college/bc...74____,00.html

Please find the mathematical basis for your theory in it.


Hey, I cited Lord Rayleigh, and he came along long before any of the others!
:-)

"Phil Allison" wrote in message
...

"Arny Krueger"
"Jim Carr"
"Phil Allison"



** The words of an ass.

Can't you do any better than calling people names?

Agreed.



** What happened to the context ????????????????????????

The remark was about the words posted.

Arny is another ass.

Ignore Phil, he's just mad because he can't contribute anything positive
to this discussion, he has neither the education nor the intelligence, nor,
obviously, the maturity!:-) In fact he reminds me a bit of someone I used to
be, though I don't think I ever got that bad! *LOL*

"Porky"


Ignore Phil, he's just mad because he can't contribute anything
positive
to this discussion, he has neither the education nor the intelligence,


** You are well named - except pigs revelling in **** have more sense
and manners than you do.


FYI I studied physics at the University of Sydney at honours level.

My IQ is at least double yours.

Unlike you and Bob, I do not have mental disabilities.




............ Phil

"ruffrecords" wrote in message

Arny Krueger wrote:
"ruffrecords" wrote in message


Jim Carr wrote:

Here's a link that you tech folks can argue about:

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




Looks good to me. Plenty of evidence of harmonic distortion (casued
by non-linearites


Agreed.


and no evidence of 50Hz sidebands arounf the 4KHz signal.


What do you call the spikes around the 4,025 Hz carrier in, for
example http://www.pcavtech.com/techtalk/dop...1-1-1+10dB.gif

That pic was not in the OP I replied to - where did it come from?

It was definately on the web site as of the date of the post I was
responding to which was posted on the 17th. I haven't changed anything on
the site for a week, since the 10th. Check the date stamp at the bottom of
the page - its updated automatically when I update the site. I don't touch
it!

Thinking about the link posted with all the analysis screenshots. As best
as I remember, they showed sidebands at +50 Hz and -50 Hz, but the Doppler
shift, if it had occurred would have been much less, on the order of a few
Hz, so the +-50Hz side bands mean absolutely nothing as far as Doppler is
concerned. The spike itself should show some tabling or spread if Doppler
shift were present. Or is the fact that I've been up about thirty hours
causing me to miss something obvious?

"Arny Krueger" wrote in message
...
"Bob Cain" wrote in message


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

Since the modulating frequency is the low frequency note, a FFT that
covers
an entire low frequency cycle would include instances of all possible
frequencies that the sidebands might have.

This begs the question as to what would happen if one measured the
position
of the sidebands in two adjacent 0.01 second periods.

If the sidebands are in fact in motion @50 Hz, then their frequencies can
be
expected to differ most of the time. Actual measurements of an actual
measured wave, processed to vastly reduce all AM distortion, does show
this
effect.

If in contrast the positions of the sidebands in two adjacent 0.02 second
periods are measured, they should be the same, and this is what one
observes.

0.01 seconds corresponds to 410 samples at 44.1 KHz, so in this
experiment,
the FFT should be based on 410 samples or less to avoid overlapping. 512
sample FFTs will overlap a bit, but are required to make the sideband
structure clear enough to comment on.

Randy Yates wrote:
ruffrecords writes:


Randy Yates wrote:

ruffrecords writes:


Randy Yates wrote:


ruffrecords writes:



If both systems are linear then they will
work in an identical manner.

That statement is absolutely correct, just as "If I am pregnant,
then I am a female." is absolutely correct.

And your point is what?

Are you REALLY this clueless and/or stupid? I give up. You apparently

do not have the facilities to reason rationally.


At least I have better manners than you.


You deserve every bit of this public ridicule. This is not a
case of bad manners, but rather a proper response.

It would be one thing to have come with an attitude of inquiry,
but you come into the discussion with blatant challenges based
on little knowledge and without the facilities to rationally
discuss.

You're like a gun-fighter with an empty cash of bullets and a broken
arm who accosts an enemy gunslinger multiple times and then whines when
he gets shot. Don't be stupid. Approach with a right attitude.

The right attitude? as exemplified by this post of yours? no thank you.

Ian

Arny Krueger wrote:
"ruffrecords" wrote in message


Jim Carr wrote:

Here's a link that you tech folks can argue about:

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




Looks good to me. Plenty of evidence of harmonic distortion (casued
by non-linearites


Agreed.


and no evidence of 50Hz sidebands arounf the 4KHz signal.


What do you call the spikes around the 4,025 Hz carrier in, for example

http://www.pcavtech.com/techtalk/dop...1-1-1+10dB.gif

That pic was not in the OP I replied to - where did it come from?

Ian

"Bob Cain" wrote in message
...


PenguiN wrote:


Uhm, no. Frequency modulation does *not* produce a flat tabletop.

http://www2.sfu.ca/sonic-studio/hand...odulation.html

Perhaps you both should review your basic signals & systems course
before continuing this discussion?

Agreed. I still don't understand why it wouldn't display
all the frequencies between the extrema equally but I'll
take your word for it. I don't know modulation theory and
this is obviously a failure of intuition.

My real argument isn't about the form or spectrum of the
modulation, it's about its existance. My question was a
tangent.


Bob, aren't they showing a 1KHz signal modulated with a 50 Hz signal?
That isn't what happens with Doppler shift, the modulation frequency will
depend on the velocity of the source, not its frequency of oscillation, and
it sure won't be sidebands at +-50Hz!, more like +-3 or 4Hz! If I'm right,
this is an example of the fundamental mis-assumptions the pro-Doppler group
is making, just like basing their logic on an analogy that doesn't meet the
necessary criteria..

"Jim Carr" wrote in message
news:6EqUc.9909$yh.5754@fed1read05...

"Bob Cain" wrote in message
...


Jim Carr wrote:
Here's a link that you tech folks can argue about:

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

What's to argue? What it all means?

Hell if I know! I was hoping you would tell me!

The sidebands at 3950 and 4050 must have to do with IM distortion or
something similar. They have absolutely nothing to do with Doppler
distortion because the maximum Doppler shift is going to be only about +-10
Hz or less and there are no sidebands showing at those frequencies. Doppler
distortion, if it exists in speakers, has to do with cone velocity, and
nothing to do with cone oscillation frequency.

Jim Carr wrote:
"Mark" wrote in message
om...


Using 344.3 m/sec for the speed of sound and the Doppler equations
found he

http://www.mathpages.com/rr/s2-04/2-04.htm


Help this poor uneducated soul, will ya? The formula you are referencing
states that if the source is at rest, there is no apparent frequency shift.
It is inherently impossible for the source to be at rest *and* create a
sound wave. After all, sound waves are compression waves, right?

Suppose you have a tank of compressed air fed through a valve that can
be modulated. This can be used to create compression waves from a
source at rest.

Ian

"Porky" wrote in message


Thinking about the link posted with all the analysis screenshots. As
best as I remember, they showed sidebands at +50 Hz and -50 Hz, but
the Doppler shift, if it had occurred would have been much less, on
the order of a few Hz, so the +-50Hz side bands mean absolutely
nothing as far as Doppler is concerned.

Not so. The fact that the Doppler shift is small is reflected in the
amplitude of the sidebands, not their frequency. The frequency of the
sideband(s) is set by the modulating frequency.

http://www.tmeg.com/esp/e_modulation/modulation.htm

http://contact.tm.agilent.com/Agilen...0-1/index.html

The spike itself should show
some tabling or spread if Doppler shift were present.

Not so, because the analysis covers a large number of cycles of the
modulated tone. If you want to look at tiny slices of the tone, which is
what I was doing below, you can see more of the actual FM effect.

Or is the fact
that I've been up about thirty hours causing me to miss something
obvious?

Lots.

"Arny Krueger" wrote in message
...
"Bob Cain" wrote in message


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

Since the modulating frequency is the low frequency note, a FFT that
covers an entire low frequency cycle would include instances of all
possible frequencies that the sidebands might have.

This begs the question as to what would happen if one measured the
position of the sidebands in two adjacent 0.01 second periods.

If the sidebands are in fact in motion @50 Hz, then their
frequencies can be expected to differ most of the time. Actual
measurements of an actual measured wave, processed to vastly reduce
all AM distortion, does show this effect.

If in contrast the positions of the sidebands in two adjacent 0.02
second periods are measured, they should be the same, and this is
what one observes.

0.01 seconds corresponds to 410 samples at 44.1 KHz, so in this
experiment, the FFT should be based on 410 samples or less to avoid
overlapping. 512 sample FFTs will overlap a bit, but are required to
make the sideband structure clear enough to comment on.

"Arny Krueger" wrote in message
...
"ruffrecords" wrote in message

Arny Krueger wrote:
"ruffrecords" wrote in message


Jim Carr wrote:

Here's a link that you tech folks can argue about:

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




Looks good to me. Plenty of evidence of harmonic distortion (casued
by non-linearites


Agreed.


and no evidence of 50Hz sidebands arounf the 4KHz signal.


What do you call the spikes around the 4,025 Hz carrier in, for
example
http://www.pcavtech.com/techtalk/dop...1-1-1+10dB.gif

That pic was not in the OP I replied to - where did it come from?

It was definately on the web site as of the date of the post I was
responding to which was posted on the 17th. I haven't changed anything on
the site for a week, since the 10th. Check the date stamp at the bottom of
the page - its updated automatically when I update the site. I don't touch
it!

It still has nothing to do with Doppler shift, the spike is clean and
sharp, indicating no small frequency shift as would occur with Doppler.

"Porky" wrote in message


Bob, aren't they showing a 1KHz signal modulated with a 50 Hz
signal?

Yes, if you're referring to http://www.pcavtech.com/techtalk/doppler/

That isn't what happens with Doppler shift, the modulation
frequency will depend on the velocity of the source, not its
frequency of oscillation,

The velocity of the source is given by the combination of the LF frequency
and the amplitude of the motion of the speaker cone.

and it sure won't be sidebands at +-50Hz!,

Yes it will, check the referernces that you have been given!

more like +-3 or 4Hz!

The actual shift of the carrier is given by the vector sum of the
sideband(s) and the carrier.

"Porky" wrote in message

"Jim Carr" wrote in message
news:6EqUc.9909$yh.5754@fed1read05...

"Bob Cain" wrote in message
...


Jim Carr wrote:
Here's a link that you tech folks can argue about:

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

What's to argue? What it all means?

Hell if I know! I was hoping you would tell me!

The sidebands at 3950 and 4050 must have to do with IM distortion or
something similar.

They are in fact mostly AM distortion - which you seem to be calling IM.

However, if one reduces AM close to zero by means of filtering and clipping,
one finds abundant FM remains.

They have absolutely nothing to do with Doppler
distortion because the maximum Doppler shift is going to be only
about +-10 Hz or less and there are no sidebands showing at those
frequencies.

The actual shift of the carrier is given by the vector sum of the carrier
and the sidebands. The three references you have been given make that clear,
but the strongest case is probably made in
http://contact.tm.agilent.com/Agilen...0-1/index.html .

Doppler distortion, if it exists in speakers, has to do
with cone velocity, and nothing to do with cone oscillation frequency.

Well, cone velocity depends on the LF frequency and amplitude of the stroke.

"Mark Simonetti" wrote in message
...
"Picture the largest loudspeaker in the universe sitting outside"
"Now add to that signal a small, high pitched, low amplitude waveform"

I couldn't of put it better myself. I was watching the argument and
watching it turn into a slanging match. I wish that wouldn't happen.
The only problem as far as I could see is that Porky was thinking of
just a singular frequency, rather than a high frequency "riding" a low
frequency.

No, I was referring to the complex sound wave generated when one mixes a
high frequency with a low frequency and applies that complex electrical
waveform to the speaker voice voil. The result is NOT a high frequency tone
riding on a low frequency tone, it's a single complex waveform containing
elements of both tones, and thus there is no Doppler distortion.

When that occurs, the train and whistle analogy indeed seems to make
sense. With a singular frequency, IMHO, it does not.

Once again, the train/whistle analogy pertains to what happens when one
discrete source of sound is riding on another discrete source of motion,
whether the other source of energy is producing sound or not. That isn't at
all what happens with a speaker and therefore it does not apply to a
speaker.

"Porky" wrote in message



It still has nothing to do with Doppler shift, the spike is clean and
sharp, indicating no small frequency shift as would occur with
Doppler.

Still havent read my references, I take it.

http://contact.tm.agilent.com/Agilen...0-1/index.html

"ruffrecords" wrote in message

Arny Krueger wrote:
"ruffrecords" wrote in message


Arny Krueger wrote:

"ruffrecords" wrote in message



Jim Carr wrote:


Here's a link that you tech folks can argue about:

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




Looks good to me. Plenty of evidence of harmonic distortion
(casued by non-linearites


Agreed.



and no evidence of 50Hz sidebands arounf the 4KHz signal.


What do you call the spikes around the 4,025 Hz carrier in, for
example
http://www.pcavtech.com/techtalk/dop...1-1-1+10dB.gif

That pic was not in the OP I replied to - where did it come from?


It was definately on the web site as of the date of the post I was
responding to which was posted on the 17th. I haven't changed
anything on the site for a week, since the 10th. Check the date
stamp at the bottom of the page - its updated automatically when I
update the site. I don't touch it!



Ah, on the web site. I just looked at what the OP linked to. Is your
pic a close up of the one he posted?

Sorry, the thread is so long that I've lost track of the OP, or what he
posted.