Sign in with
Sign up | Sign in
Your question

Bob Cain Needs to Accept Reality and Acknowledge Defeat

Tags:
Last response: in Home Audio
Share
Anonymous
August 20, 2004 12:01:47 AM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

I have provided direct experimental measurements of dynamic Doppler
shift. I have also provided a reference to the analysis of
instantaneous dynamic Doppler shift that is given in a classical
textbook on Acoustics by a well respected and reputable author. It is
time for Bob Cain and his equally mindless followers to accept reality
and to acknowledge defeat. While the senseless debate over the
existence of dynamic Doppler shift will undoubtedly continue among the
audio illiterates who prefer to deny reality rather than accept
experimental proof and/or who are incapable of understanding the
applicable math, from a purely scientific perspective, the issue is
settled and the debate is over.
Anonymous
August 20, 2004 4:36:23 AM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

The Ghost wrote:

> I have provided direct experimental measurements of dynamic Doppler
> shift. I have also provided a reference to the analysis of
> instantaneous dynamic Doppler shift that is given in a classical
> textbook on Acoustics by a well respected and reputable author. It is
> time for Bob Cain and his equally mindless followers to accept reality
> and to acknowledge defeat. While the senseless debate over the
> existence of dynamic Doppler shift will undoubtedly continue among the
> audio illiterates who prefer to deny reality rather than accept
> experimental proof and/or who are incapable of understanding the
> applicable math, from a purely scientific perspective, the issue is
> settled and the debate is over.

ROTFLOL!

Your experiment does not separate variables. Try it
sometime. Other than corrupted data are you ever going to
offer anything substantive to this discussion?

Why, if it does, do you think Doppler distortion exists? I
take it from your implicit support that you accept the
vernacular argument. How about a predictive theory that
tells what to expect quantitatively. Start with the piston
in a tube (infinite plane generating a plane wave) and
graduate to a piston in a baffle. It's totally different
depending on the configuration but I suppose you knew that.
Almost none of it occurs in the very near field of the
speaker, but I'm sure you knew that.

Actually, I've come to realize that you are a fraud. If you
knew anything it is certain you'd be spouting it. Perhaps
once you did but it seems to have been eaten by the acid of
your disturbed mind. Or are we supposed to accept your
brilliance based on your nasty attitude and the carping it
produces? You are a legend in your own mind. The reality
of your legend is quite different.


Bob
--

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

A. Einstein
Anonymous
August 20, 2004 7:55:52 AM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

"Bob Cain" <arcane@arcanemethods.com> wrote in message
news:cg493k024ps@enews2.newsguy.com

> Your experiment does not separate variables.

But mine does.
Related resources
Can't find your answer ? Ask !
Anonymous
August 20, 2004 7:55:53 AM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

Arny Krueger wrote:

> "Bob Cain" <arcane@arcanemethods.com> wrote in message
> news:cg493k024ps@enews2.newsguy.com
>
>
>>Your experiment does not separate variables.
>
>
> But mine does.

Please explain once again for this tired old brain how,
specifically, it does that. I honestly didn't see that in
what you've written.


Thanks,

Bob
--

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

A. Einstein
Anonymous
August 20, 2004 8:33:09 AM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

> How about a predictive theory that tells what to
> expect quantitatively?

I have repeatedly stated the simple mathematical steps needed to derive a useful
formula. I'm not going to do this for you, Bob. If you don't have the trivial
knowledge or skill to do this for yourself -- then why should you be interested
in the "maths" of Doppler shift in the first place?

It's about time you let the issue drop.
Anonymous
August 20, 2004 10:35:27 AM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

"Bob Cain" <arcane@arcanemethods.com> wrote in message
news:cg4dn356e4@enews3.newsguy.com
> Arny Krueger wrote:
>
>> "Bob Cain" <arcane@arcanemethods.com> wrote in message
>> news:cg493k024ps@enews2.newsguy.com
>>
>>
>>> Your experiment does not separate variables.
>>
>>
>> But mine does.
>
> Please explain once again for this tired old brain how,
> specifically, it does that. I honestly didn't see that in
> what you've written.

I've written about the fact that the test signal from the microphone was
bandpass filtered and tremendously clipped, thus removing all amplitude
modulation. Sidebands characteristic of FM remained.
Anonymous
August 20, 2004 10:58:54 AM

Archived from groups: rec.audio.pro (More info?)

Doppler comes and Doppler goes....
Anonymous
August 20, 2004 2:10:53 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

Arny Krueger wrote:


>>Please explain once again for this tired old brain how,
>>specifically, it does that. I honestly didn't see that in
>>what you've written.
>
>
> I've written about the fact that the test signal from the microphone was
> bandpass filtered and tremendously clipped, thus removing all amplitude
> modulation. Sidebands characteristic of FM remained.

Sorry, Arny. This in no way eliminates the effects of the
mechanical imperfections of the speaker. What would is
optical measurement of its motion compared to the sound it
generates. There are likely other, more accessable ways, to
measure that motion.


Bob
--

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

A. Einstein
Anonymous
August 20, 2004 2:14:29 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

William Sommerwerck wrote:

>>How about a predictive theory that tells what to
>>expect quantitatively?
>
>
> I have repeatedly stated the simple mathematical steps needed to derive a useful
> formula. I'm not going to do this for you, Bob.

The fact that you believe it so simple truly tells the
degree to which such a comment is credible from you.

Fact is, you couldn't because you don't understand it at
all. I'm getting closer and do actually have hope that with
some outside assistance a correct mathematical expression
can be produced for some common cases.


Bob
--

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

A. Einstein
Anonymous
August 20, 2004 3:04:51 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

>> I have repeatedly stated the simple mathematical steps needed
>> to derive a useful formula. I'm not going to do this for you, Bob.

> The fact that you believe it so simple truly tells the
> degree to which such a comment is credible from you.

> Fact is, you couldn't because you don't understand it at
> all. I'm getting closer and do actually have hope that with
> some outside assistance a correct mathematical expression
> can be produced for some common cases.

It is precisely because I understand it that I realize how simple it is. Note
your own signature! (Which, by the way, I believe is a misquote.) You are
overanalyzing something that is not complicated.

Any number of people in this group, including Arny, Fletcher, Steve, Ralph,
Waldo, and Emerson, could easily throw together the equations. It's trivial.

Bob, I have no trouble with you thinking you're bright, clever, and insightful.
(Heck, I think _I_ am.) I do object when you think others aren't.

I, too, occasionally raise points that other people just don't seem to "get."
But I BACK OFF after a while, and think about them some more.
Anonymous
August 20, 2004 4:36:44 PM

Archived from groups: rec.audio.tech (More info?)

On Fri, 20 Aug 2004 00:36:23 -0700, Bob Cain
<arcane@arcanemethods.com> wrote:

...stuff deleted....

>Why, if it does, do you think Doppler distortion exists? I
>take it from your implicit support that you accept the
>vernacular argument. How about a predictive theory that
>tells what to expect quantitatively. Start with the piston
>in a tube (infinite plane generating a plane wave) and
>graduate to a piston in a baffle. It's totally different
>depending on the configuration but I suppose you knew that.
> Almost none of it occurs in the very near field of the
>speaker, but I'm sure you knew that.
>

I just waded through "Theoretical Acoustics", Morse and
Ingard,1968,pp698-737. The apparent recieved frequency shift from a
moving monopole, dipole, plane wave source (piston cylinder), are all
the same, if you are 90 degrees to the source. The frequency shift
(subsonic case) all follows the simple case. This is a relativity
issue..... we're dealing with two coordinate systems that are moving
relative to each other.
Distortion is not an issue here, just frequency shift.
w1=w0/(1-M) where w1 is apparent freq.
w0 is freq from moving source
M is v/c where v is velocity of source, c is speed
of sound
Distortion is a whole other ball game, depending on velocity profile
with respect to time and the frequency shift from the above equations.

I have tried to follow the various arguments, but I have difficulty
making sense out of most of them. In most cases "you're both right",
but arguing from very different perspectives, or someone is focussing
on a very narrow line of reasoning, different from his "rival". I
hated even to get into this argument because of the mudslinging from
frustrated "players".
Doppler shift is real.... try it! In order to hear it readily, you
need a low freq. source 1-100Hz (the brain can't easily detect other
modulating freq. ... around 60 Hz is best), and a 1000 Hz signal. The
low freq. will have to be very stong, a hefty woofer (long throw) will
do. The lower freq. will enable you to hear the shifting frequencies,
and thus discriminate against AM modulation. From my experience, high
modulation index (M)is the most audible, M=(freq shift)/(modulating
freq). M should be larger than 0.5 to be readily noticed.

-Paul
...............................................................
Paul Guy
Somewhere in the Nova Scotia fog
Anonymous
August 20, 2004 5:22:28 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

Bob Cain <arcane@arcanemethods.com> wrote in message news:<cg493k024ps@enews2.newsguy.com>...
> The Ghost wrote:
>
> > I have provided direct experimental measurements of dynamic Doppler
> > shift. I have also provided a reference to the analysis of
> > instantaneous dynamic Doppler shift that is given in a classical
> > textbook on Acoustics by a well respected and reputable author. It is
> > time for Bob Cain and his equally mindless followers to accept reality
> > and to acknowledge defeat. While the senseless debate over the
> > existence of dynamic Doppler shift will undoubtedly continue among the
> > audio illiterates who prefer to deny reality rather than accept
> > experimental proof and/or who are incapable of understanding the
> > applicable math, from a purely scientific perspective, the issue is
> > settled and the debate is over.
>
> ROTFLOL!
>
> Your experiment does not separate variables. Try it
> sometime. Other than corrupted data are you ever going to
> offer anything substantive to this discussion?
>
> Why, if it does, do you think Doppler distortion exists? I
> take it from your implicit support that you accept the
> vernacular argument. How about a predictive theory that
> tells what to expect quantitatively. Start with the piston
> in a tube (infinite plane generating a plane wave) and
> graduate to a piston in a baffle. It's totally different
> depending on the configuration but I suppose you knew that.
> Almost none of it occurs in the very near field of the
> speaker, but I'm sure you knew that.
>
> Actually, I've come to realize that you are a fraud. If you
> knew anything it is certain you'd be spouting it. Perhaps
> once you did but it seems to have been eaten by the acid of
> your disturbed mind. Or are we supposed to accept your
> brilliance based on your nasty attitude and the carping it
> produces? You are a legend in your own mind. The reality
> of your legend is quite different.

There are many people who pay me handsomely for my knowledge,
experience and technical ability, and it is their opinions, not yours,
that are important and that matter. If you are unable to recognize
and appreciate the validity and value of the information that I have
provided, that is your problem, not mine. I have gone out and caught
the food, prepared the meal and put it on the table in front of you.
If you expect me to spoon feed the meal to you, that isn't going to
happen. With regard to your most recent ad hominem attack, it is not
something that is either new or unexpected. Such ad hominem attacks
directed at me in alt.sci.physics.acoustics have been a trademark of
yours for the past three or four years. However, your most recent ad
hominem attacks in the audio groups have been much more vitriolic than
those in the past. No doubt that is because I have come onto your
turf where you are on center stage and all of your audio buddies are
watching, and because you are loosing the debate.
Anonymous
August 20, 2004 5:44:26 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

Bob Cain wrote:

>
>
> William Sommerwerck wrote:
>
>>> How about a predictive theory that tells what to
>>> expect quantitatively?
>>
>>
>>
>> I have repeatedly stated the simple mathematical steps needed to
>> derive a useful
>> formula. I'm not going to do this for you, Bob.
>
>
> The fact that you believe it so simple truly tells the degree to which
> such a comment is credible from you.

That wasn't at all fair, Willian, and I appologize. I
started with the standard assumption that you are making
too. What it led to mathematically was an infinite regress
or recursion where a function was defined in terms of
itself. I could find absolutely no way out of this dillema.
While in some similar situations, there is a kind of
convergence in the limit, this did not appear to be one of
them, in fact it predicted classical recursive chaos that is
essentially unpredictable. Numerical simulation also showed
that by producing a spectrum that was nearly white noise.

I didn't believe that because it doesn't sound like that and
I took that as my first evidence beyond simple intuition
that something was wrong with the accepted model.

I invite you to try where I have failed with that model.


Bob
--

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

A. Einstein
Anonymous
August 20, 2004 6:07:27 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

In a never-ending thread crossposted to:
rec.audio.pro,
rec.audio.tech,
alt.music.home-studio and
alt.sci.physics.acoustics,
Bob Cain <arcane@arcanemethods.com> wrote:

>
>
>Arny Krueger wrote:
>
>
>>>Please explain once again for this tired old brain how,
>>>specifically, it does that. I honestly didn't see that in
>>>what you've written.
>>
>>
>> I've written about the fact that the test signal from the microphone was
>> bandpass filtered and tremendously clipped, thus removing all amplitude
>> modulation. Sidebands characteristic of FM remained.
>
>Sorry, Arny. This in no way eliminates the effects of the
>mechanical imperfections of the speaker. What would is
>optical measurement of its motion compared to the sound it
>generates.

Of course the optical measurements won't show the same doppler
distortion unless the cone is moving faster by about six orders of
magnitude. :) 
And even then, you'll have optical measurement of the cone's
movement at one point, and not the sound it produces. You could
measure it at many points and do an average, that should come close.

>There are likely other, more accessable ways, to
>measure that motion.
>
>
>Bob

-----
http://mindspring.com/~benbradley
Anonymous
August 20, 2004 6:30:01 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

"William Sommerwerck" <williams@nwlink.com> wrote in message
news:10iboegsscd28c@corp.supernews.com...
> > How about a predictive theory that tells what to
> > expect quantitatively?
>
> I have repeatedly stated the simple mathematical steps needed to derive a
useful
> formula. I'm not going to do this for you, Bob. If you don't have the
trivial
> knowledge or skill to do this for yourself -- then why should you be
interested
> in the "maths" of Doppler shift in the first place?
>
> It's about time you let the issue drop.
>

I can't tell from whence William posts, so I'll continue the cross-posting.

With all due respect, your assertion that this is simple math is simply not
true. Taking the basic Doppler formula and making it into a time-variant
formula requires knowledge of calculus, and the average Joe (no reflection
upon Bob intended) does not consider calculus simple. Instead of repeatedly
berating Bob for failing to grasp the seemingly obvious, why don't you post
the formula for all to see?

--
Michael Ellis
first initial last name at pesa commercial account
Anonymous
August 20, 2004 6:30:02 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

> With all due respect, your assertion that this is simple math is simply not
> true. Taking the basic Doppler formula and making it into a time-variant
> formula requires knowledge of calculus, and the average Joe (no reflection
> upon Bob intended) does not consider calculus simple. Instead of repeatedly
> berating Bob for failing to grasp the seemingly obvious, why don't you post
> the formula for all to see?

What is so complicated about plugging the velocity of the cone into the Doppler
formula?

You then have an expression in which the frequency shift varies as the sine of
the frequency moving the cone -- in other words, a carrier (the high frequency)
FM-modulated by the cone displacement-frequency.

Once you've figured out the modulation index, you can look up the sideband
amplitudes from a table of Bessel functions.

This is trivial stuff, guys.
Anonymous
August 20, 2004 6:30:02 PM

Archived from groups: rec.audio.pro (More info?)

Michael W. Ellis wrote:
> "William Sommerwerck" <williams@nwlink.com> wrote in message
> news:10iboegsscd28c@corp.supernews.com...
>
>>>How about a predictive theory that tells what to
>>>expect quantitatively?
>>
>>I have repeatedly stated the simple mathematical steps needed to derive a
>
> useful
>
>>formula. I'm not going to do this for you, Bob. If you don't have the
>
> trivial
>
>>knowledge or skill to do this for yourself -- then why should you be
>
> interested
>
>>in the "maths" of Doppler shift in the first place?
>>
>>It's about time you let the issue drop.
>>
>
>
> I can't tell from whence William posts, so I'll continue the cross-posting.
>
> With all due respect, your assertion that this is simple math is simply not
> true. Taking the basic Doppler formula and making it into a time-variant
> formula requires knowledge of calculus, and the average Joe (no reflection
> upon Bob intended) does not consider calculus simple. Instead of repeatedly
> berating Bob for failing to grasp the seemingly obvious, why don't you post
> the formula for all to see?
>


Right, "obvious" doesn't mean "true". Lots of things are accepted as
true even though they started out as "counterintuitive".
Anonymous
August 20, 2004 7:07:23 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

"William Sommerwerck" <williams@nwlink.com> wrote in message
news:10iclet9k6ucb1c@corp.supernews.com...
> > With all due respect, your assertion that this is simple math is simply
not
> > true. Taking the basic Doppler formula and making it into a time-variant
> > formula requires knowledge of calculus, and the average Joe (no
reflection
> > upon Bob intended) does not consider calculus simple. Instead of
repeatedly
> > berating Bob for failing to grasp the seemingly obvious, why don't you
post
> > the formula for all to see?
>
> What is so complicated about plugging the velocity of the cone into the
Doppler
> formula?
>
> You then have an expression in which the frequency shift varies as the
sine of
> the frequency moving the cone -- in other words, a carrier (the high
frequency)
> FM-modulated by the cone displacement-frequency.
>
> Once you've figured out the modulation index, you can look up the sideband
> amplitudes from a table of Bessel functions.

You, sir, seem to have made my point.

> This is trivial stuff, guys.

Validation by repetition?

--
Michael Ellis
first initial last name at pesa commercial account
Anonymous
August 20, 2004 7:10:52 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

"Bob Cain" <arcane@arcanemethods.com> wrote in message
news:cg5aov22ppj@enews4.newsguy.com
> Arny Krueger wrote:
>
>
>>> Please explain once again for this tired old brain how,
>>> specifically, it does that. I honestly didn't see that in
>>> what you've written.
>>
>>
>> I've written about the fact that the test signal from the microphone
>> was bandpass filtered and tremendously clipped, thus removing all
>> amplitude modulation. Sidebands characteristic of FM remained.
>
> Sorry, Arny. This in no way eliminates the effects of the
> mechanical imperfections of the speaker.

I thought this was about real-world speakers. If the speaker were free of
mechanical imperfections, there would be no Doppler, as well.

> What would is optical measurement of its motion compared to the sound it
> generates.

Use papal to contribute enough cash to my account, and you've got a deal!

> There are likely other, more accessible ways, to
> measure that motion.

Gosh, I thought there was a free laser inferiometer in this! ;-)
Anonymous
August 20, 2004 7:10:53 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

> I thought this was about real-world speakers. If the speaker were free
> of mechanical imperfections, there would be no Doppler, as well.

Am I missing something? Doppler effects (as opposed to FM effects) have nothing
to do with the speaker's perfection, or lack thereof.
Anonymous
August 20, 2004 7:23:35 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

>> The fact that you believe it so simple truly tells the
>> degree to which such a comment is credible from you.

> That wasn't at all fair, Willian, and I appologize. I started
> with the standard assumption that you are making, too.

That isn't obvious to me, except possibly for the point I make below -- qv.


> What it led to mathematically was an infinite regress
> or recursion where a function was defined in terms of
> itself. I could find absolutely no way out of this dillema.

Not every problem has a simple or closed solution. A good approximation can be
completely satisfactory. That's why we have tables of integrals for functions
that don't have expressable integrals. (Can't think of the right word.)

Remember the scene in "The Day the Earth Stood Still" where the Einstein
character asks Klaatu about the fact the blackboard formula doesn't have an
exact solution? Klaatu replies that the approximation is good enough to get him
from planet to planet.

From my perspective, you're making something complicated out of something
simple. I might be wrong, but it seems very plain to me. Not because I would
like it to be, but because I think this is a fundamentally simple problem with a
fundamentally simple analysis.

Point made below: I believe that my explanation and the "simple" corresponding
math is "correct," with one obvious omission -- it does not model the modulation
of the lower frequency by the upper -- if such an effect exists. Is this what
causes the "infinite regression" in your treatment?

One other point... One of the reasons I'm so fussy and argumentative about this
issue is that, over the years, I've been most-impressed by scientists who give
simple, elegant explanations. (Correct explanations, of course!) I consciously
try to model my explanations accordingly.


> While in some similar situations, there is a kind of
> convergence in the limit, this did not appear to be one of
> them, in fact it predicted classical recursive chaos that is
> essentially unpredictable. Numerical simulation also showed
> that by producing a spectrum that was nearly white noise.

> I didn't believe that because it doesn't sound like that and
> I took that as my first evidence beyond simple intuition
> that something was wrong with the accepted model.

> I invite you to try where I have failed with that model.
Anonymous
August 20, 2004 7:42:39 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

"William Sommerwerck" <williams@nwlink.com> wrote in message
news:10icjfee40fs82b@corp.supernews.com
>> I thought this was about real-world speakers. If the speaker were
>> free of mechanical imperfections, there would be no Doppler, as well.
>
> Am I missing something? Doppler effects (as opposed to FM effects)
> have nothing to do with the speaker's perfection, or lack thereof.

For the purpose of discussion, let's agree that the ideal speaker has no
Doppler distortion as long as the receiver is fixed in the same coordinate
system as the chassis and enclosure of the speaker is fixed in.

If such a speaker actually exists, then it makes sense to say that it is
ideal w/r/t Doppler distortion, no?

I think most of us agree that making a speaker cover a limited frequency
range and have limited diaphragm motion, would reduce Doppler. So, we know
that perfection is approachable.

I also believe that some of us agree that a speaker can be made with zero
diaphragm motion - namely a thermal speaker, a ionic speaker being an
example of such a thing.

Therefore it may be possible to have a speaker that either is perfect, or
approaches perfection w/r/t Doppler distortion.
Anonymous
August 20, 2004 7:42:40 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

>>> I thought this was about real-world speakers. If the speaker were
>>> free of mechanical imperfections, there would be no Doppler, as well.

No! The Doppler effect has nothing to do with the "quality" of the speaker, any
more than it has to do with whether the train is steam or diesel-electric. The
Doppler effect is a property of the laws of nature.


>> Am I missing something? Doppler effects (as opposed to FM effects)
>> have nothing to do with the speaker's perfection, or lack thereof.

> For the purpose of discussion, let's agree that the ideal speaker has no
> Doppler distortion as long as the receiver is fixed in the same coordinate
> system as the chassis and enclosure of the speaker is fixed in.

No way. You still have the relative motion produced by the "large" excursion of
the driver, which Doppler-modulates higher-frequency sounds. As you yourself
pointed out, the Doppler would be cancelled by moving the listener the same way
the driver moves.


> If such a speaker actually exists, then it makes sense to say that it is
> ideal w/r/t Doppler distortion, no?

> I think most of us agree that making a speaker cover a limited frequency
> range and have limited diaphragm motion, would reduce Doppler. So, we know
> that perfection is approachable.

> I also believe that some of us agree that a speaker can be made with zero
> diaphragm motion - namely a thermal speaker, a ionic speaker being an
> example of such a thing.

> Therefore it may be possible to have a speaker that either is perfect, or
> approaches perfection w/r/t Doppler distortion.

I think I see your point, but the Doppler distortion produced by a "vibrating"
speaker is inherent in the laws of nature -- it has nothing to do with the
"quality" of the speaker. Even if the cone's motion perfectly followed the input
waveform, you would still have the Doppler effect.

The idea that a pure sine wave signal Doppler-phase-modulates ITSELF is one that
I'm trying to digest at the moment.
Anonymous
August 20, 2004 10:44:27 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

William Sommerwerck wrote:

>>>>I thought this was about real-world speakers. If the speaker were
>>>>free of mechanical imperfections, there would be no Doppler, as well.
>
>
> No! The Doppler effect has nothing to do with the "quality" of the speaker, any
> more than it has to do with whether the train is steam or diesel-electric. The
> Doppler effect is a property of the laws of nature.

Hey, William, we agree on something again! That's why it is
essential to remove the other effects from corrupting the
data if we are investigating the Doppler phenomenon.


> No way. You still have the relative motion produced by the "large" excursion of
> the driver,

This is incorrect. That is not what causes it.

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

Then you can stop before that digestion is ruined. It
doesn't happen and its prediction follows from the false
premise as to what happens to cause Doppler distortion.
With the real Doppler distortion, there will be no such self
modulation


Bob
--

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

A. Einstein
Anonymous
August 20, 2004 10:45:57 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

William Sommerwerck wrote:

> Any number of people in this group, including Arny, Fletcher, Steve, Ralph,
> Waldo, and Emerson, could easily throw together the equations. It's trivial.

Then why hasn't anyone? That would give something concrete
to prove or disprove.


Bob
--

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

A. Einstein
Anonymous
August 20, 2004 10:52:10 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

William Sommerwerck wrote:

> What is so complicated about plugging the velocity of the cone into the Doppler
> formula?
>
> You then have an expression in which the frequency shift varies as the sine of
> the frequency moving the cone -- in other words, a carrier (the high frequency)
> FM-modulated by the cone displacement-frequency.
>
> Once you've figured out the modulation index, you can look up the sideband
> amplitudes from a table of Bessel functions.
>
> This is trivial stuff, guys.

Then why don't you just do it? I simply don't get this
argument of yours when you refuse to do anything about
backing it up despite its simplicity. I told you that I
tried and failed to get anything meaningful. If it so easy,
please show me how.


Bob
--

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

A. Einstein
Anonymous
August 20, 2004 10:55:56 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

The Ghost wrote:

> If you are unable to recognize
> and appreciate the validity and value of the information that I have
> provided, that is your problem, not mine.

You have offered no such information; zip, nada, nothing.
You have only postured as you are continuing to do in the
post I'm referencing. Ad hominem is exactly right. You
deserve no more.


Bob
--

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

A. Einstein
Anonymous
August 20, 2004 11:33:09 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

William Sommerwerck wrote:

>>>The fact that you believe it so simple truly tells the
>>>degree to which such a comment is credible from you.
>
>
>>That wasn't at all fair, Willian, and I appologize. I started
>>with the standard assumption that you are making, too.
>
>
> That isn't obvious to me, except possibly for the point I make below -- qv.

Then just take my word for it. Heavy sigh.

Please give it a shot yourself.


Bob
--

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

A. Einstein
Anonymous
August 20, 2004 11:51:45 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

>> No way. You still have the relative motion produced by the
>> "large" excursion of the driver,

> This is incorrect. That is not what causes it.

Then what does?
Anonymous
August 20, 2004 11:53:06 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

>> This is trivial stuff, guys.

> Then why don't you just do it? I simply don't get this
> argument of yours when you refuse to do anything about
> backing it up despite its simplicity. I told you that I
> tried and failed to get anything meaningful. If it so easy,
> please show me how.

Because...

A: I didn't raise the issue in the first place.

B: I've clearly explained the steps involved.

C: I'm not going to do your work for you.
August 21, 2004 12:06:24 AM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

> What is so complicated about plugging the velocity of the cone into the Doppler
> formula?
>
> You then have an expression in which the frequency shift varies as the sine of
> the frequency moving the cone -- in other words, a carrier (the high frequency)
> FM-modulated by the cone displacement-frequency.
>
> Once you've figured out the modulation index, you can look up the sideband
> amplitudes from a table of Bessel functions.
>
> This is trivial stuff, guys.

I have already done this in a previous posting and the results agreed
with what was seen on the spectrum analyzer.

Mark
Anonymous
August 21, 2004 12:46:58 AM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

William Sommerwerck wrote:

>>>No way. You still have the relative motion produced by the
>>>"large" excursion of the driver,
>
>
>>This is incorrect. That is not what causes it.
>
>
> Then what does?

It occurs between any frequencies whose tranfer function
betweeen source and receiver are different (perhaps just in
magnitude, I'm not sure yet.) In general, if the transfer
function is frequency dependant then there will be mixing,
and in general the amount of it depends on the amount of
difference.

In the tube example, the transfer function is constant and
real for all frequencies so that it doesn't occur there.


Bob
--

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

A. Einstein
Anonymous
August 21, 2004 1:30:15 AM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

"William Sommerwerck" <williams@nwlink.com> wrote in message
news:10idec264shcj8b@corp.supernews.com...

> A: I didn't raise the issue in the first place.

Nobody expects the person who asked for help to be the one who provides it.

> B: I've clearly explained the steps involved.

Chiseling a statue is easy. Just knock off all the bits that don't look like
your subject.

> C: I'm not going to do your work for you.

But you *will* spend twice as much time posting about how you won't take the
time to do it.

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

Now, I make no claims of expertise or training, so don't ridicule me for
asking what if I have a lower frequency of 50 and a higher frequency of 51.
How can I use the standard formula? What's Fs?
Anonymous
August 21, 2004 1:58:12 AM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

Bob Cain wrote:
>
>
> William Sommerwerck wrote:
>
> It occurs between any frequencies whose tranfer function betweeen source
> and receiver are different (perhaps just in magnitude, I'm not sure
> yet.) In general, if the transfer function is frequency dependant then
> there will be mixing, and in general the amount of it depends on the
> amount of difference.
>
> In the tube example, the transfer function is constant and real for all
> frequencies so that it doesn't occur there.
^
and at all distances



A bit more to close it off unless there is disagreement.

An illustration of where Doppler distortion clearly does
occur is the speaker emiting a tone while swinging wide at
the end of a long rope. There is time varying Doppler shift
here because the transfer function from speaker to a mic in
the far field has a very small value (the coupling is small)
at the low, swinging frequency but a much higher value (the
coupling is fairly large) for the tone. The end result is
obvious.

Less obvious is that in the very near field of a speaker, a
low to midlin frequency will couple just as well as a higher
frequency, such that close up little or no Doppler
distortion can be measured while at the far field, the lower
frequency, being much less directive, will couple much more
poorly and will thus mix more with the higher frequency
component. In this case, the Doppler distortion is not
occuring in the region immediately adjacent to the cone but
happens gradually with increasing distance. In the limit as
you approach the piston, it ceases to exist. Up close, my
hat and stomach are quite safe. Further out they are both
more endangered.

Can you see that this is quite different than what has been
commonly described as occuring due to relative motion of
high and low frequency components at the piston/air interface?


Bob
--

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

A. Einstein
Anonymous
August 21, 2004 1:59:43 AM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

William Sommerwerck wrote:

>>>This is trivial stuff, guys.
>
>
>>Then why don't you just do it? I simply don't get this
>>argument of yours when you refuse to do anything about
>>backing it up despite its simplicity. I told you that I
>>tried and failed to get anything meaningful. If it so easy,
>>please show me how.
>
>
> Because...
>
> A: I didn't raise the issue in the first place.
>
> B: I've clearly explained the steps involved.
>
> C: I'm not going to do your work for you.

William, that is an utterly transparent cop-out.


Bob
--

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

A. Einstein
Anonymous
August 21, 2004 2:02:34 AM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

Mark wrote:

>>What is so complicated about plugging the velocity of the cone into the Doppler
>>formula?
>>
>>You then have an expression in which the frequency shift varies as the sine of
>>the frequency moving the cone -- in other words, a carrier (the high frequency)
>>FM-modulated by the cone displacement-frequency.
>>
>>Once you've figured out the modulation index, you can look up the sideband
>>amplitudes from a table of Bessel functions.
>>
>>This is trivial stuff, guys.
>
>
> I have already done this in a previous posting and the results agreed
> with what was seen on the spectrum analyzer.

Did what, Mark? I'm sorry but I missed a predictive,
quantitative equation for the Doppler distortion.


Bob
--

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

A. Einstein
Anonymous
August 21, 2004 9:18:30 AM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

> An illustration of where Doppler distortion clearly does occur is the
> speaker emiting a tone while swinging wide at the end of a long rope.
> There is time varying Doppler shift here because the transfer function
> from speaker to a mic in the far field has a very small value (the
> coupling is small) at the low, swinging frequency but a much higher value
> (the coupling is fairly large) for the tone. The end result is obvious.

I think another possibility is what might happen if the speaker were being
driven with a large signal below resonance, where the cone just flops around
wildly without coupling much energy to the surrounding air, while
simultaneously radiating higher frequencies above resonance. I think you
could get Doppler in that case. Variations in frequency response due to cone
vibrational modes might also cause measurable Doppler, but not due to the
fundamental principles of speaker operation.
Anonymous
August 21, 2004 9:28:12 AM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

>> Then what does?

> It occurs between any frequencies whose tranfer function
> betweeen source and receiver are different (perhaps just in
> magnitude, I'm not sure yet.) In general, if the transfer
> function is frequency dependant then there will be mixing,
> and in general the amount of it depends on the amount of
> difference.

> In the tube example, the transfer function is constant and
> real for all frequencies so that it doesn't occur there.

Forgive me for "appealing to authority," but what you say contradicts every
physics book I've read. Worse, what you say is inconsistent (as far as I can
tell) with several broadly accepted principles of math and physics.

The Doppler effect IS NOT the product (pun intended) of non-linearities or
variations in transfer function. It occurs (in air) because the sound source (or
receiver) is moving with respect to the medium.
Anonymous
August 21, 2004 9:34:48 AM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

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

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

As for multiple frequencies...

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

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


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

This is a valid point. But hold off for a while. We still haven't resolved the
basic question.
Anonymous
August 21, 2004 9:38:36 AM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

>> A: I didn't raise the issue in the first place.

>> B: I've clearly explained the steps involved.

>> C: I'm not going to do your work for you.

> William, that is an utterly transparent cop-out.

So if I tell you how to design op-amp circuits, in words, but don't actually
build them, that proves I don't know how to design op-amp circuits? Spare me.

Bob, you're just a lazy SOB who won't lift a finger to work through the problem.

IT'S EFFING TRIVIAL!!! Except for looking up the Bessel values, you can do the
whole thing in a minute or two.

SPARE ME YOUR STUPID COMPLAINING. DO THE EFFING MATH.
Anonymous
August 21, 2004 2:05:38 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

William Sommerwerck wrote:

>>I don't think you can do it. Your prior explanation about using the standard
>>Doppler Effect formula does not apply because it assumes a constant linear
>>motion and a single frequency. It does not handle oscillating motion or
>>multiple frequencies.
>
>
> It does if you replace the constant velocity with the varying velocity of the
> cone, which is a trivial derivation and insertion. Duh!

That's simply wrong.

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

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

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

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


Bob
--

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

A. Einstein
Anonymous
August 21, 2004 2:07:04 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

William Sommerwerck wrote:


> SPARE ME YOUR STUPID COMPLAINING. DO THE EFFING MATH.
>

Plonk.


Bob
--

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

A. Einstein
Anonymous
August 21, 2004 3:02:02 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

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

> That's simply wrong.

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


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

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

Tell that to the people who agree with my reasoning.

I have a degree in electrical engineering. Which doesn't prove anything, of
course. But I remain amazed at the number of people who have a degree in XYZ --
and don't understand it worth a damn.
Anonymous
August 21, 2004 3:17:45 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

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

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

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


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

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


As I said, I hate to appeal to authority. But I'm going to call Dr. Allen Hill
and see if he has any thoughts on the subject. I'm sure he'll have an elegant,
incisive explanation.
Anonymous
August 21, 2004 3:33:41 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

William Sommerwerck wrote:

>>I don't think you can do it. Your prior explanation about using the standard
>>Doppler Effect formula does not apply because it assumes a constant linear
>>motion and a single frequency. It does not handle oscillating motion or
>>multiple frequencies.
>
>
> It does if you replace the constant velocity with the varying velocity of the
> cone, which is a trivial derivation and insertion. Duh!

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

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

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

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

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


Bob
--

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

A. Einstein
Anonymous
August 21, 2004 8:33:19 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

Bob Cain wrote:

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

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

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


Bob
--

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

A. Einstein
Anonymous
August 21, 2004 9:22:25 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

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

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

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

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

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

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

>> Now, I make no claims of expertise or training, so don't ridicule me for
>> asking what if I have a lower frequency of 50 and a higher frequency of
>> 51.
>> How can I use the standard formula? What's Fs?
>
> This is a valid point. But hold off for a while. We still haven't resolved
> the
> basic question.

Bingo! I don't think anyone on this thread (at least in rec.audio.tech) has
yet presented the fundamental physics relating to this problem so no one
really knows that they're talking about (including myself -- no offense).
Anonymous
August 21, 2004 9:22:26 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

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

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

You are overanalyzing the obvious.


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

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


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

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

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


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

Agreed. But I'm sticking by my analysis.

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

The reason your analysis is wrong is because YOU'RE NOT ASKING THE RIGHT
QUESTIONS.
Anonymous
August 21, 2004 10:01:57 PM

Archived from groups: rec.audio.tech (More info?)

By the way, we'll know when we have the right solution when we have a set of
formulas that can accurately predict how much Doppler shift will occcur, and
then you can reliably measure the effect experimentally. The measured and
predicted effect must agree to a reasonable degree of accuracy, otherwise,
you simply don't have the right solution. AFAIK, this hasn't happened yet on
rec.audio.tech, which is the only thread I've been following.
Anonymous
August 21, 2004 10:33:04 PM

Archived from groups: rec.audio.pro,rec.audio.tech,alt.music.home-studio,alt.sci.physics.acoustics (More info?)

"William Sommerwerck" <williams@nwlink.com> wrote in message
news:10if47ntn7ca605@corp.supernews.com...
>>> It does if you replace the constant velocity with the varying velocity
>>> of the cone, which is a trivial derivation and insertion. Duh!
>
>> Be careful... If you setup the problem wrong, you'll come to the wrong
>> conclusion. One radiator is emitting two frequencies coupled to the
>> same air mass isn't the same as one radiator moving about inside an
>> air mass, which is what the Doppler formula is about. The vs term in
>> the Doppler formula isn't radiating energy or coupled to the air mass.
>
> You are overanalyzing the obvious.

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

>> If the low frequency is coupled to the air mass in such a way that it is
>> radiating sound as effiently as it is at the higher frequencies, the
>> energy
>> transfer is different.
>
> The energy transfer produced by the LF movement of the cone has NOTHING to
> do
> with the analysis of the problem, any more than the movement of the
> surrounding
> air that "sticks" to the train.
>
>
>> If the radiator is just "flopping around" at the lower frequency without
>> creating sound waves, the higher frequency will be Doppler-shifted.
>
> And what does the audibility of the LF movement of the driver have to do
> with
> whether Doppler shift is created? NOTHING WHATEVER.

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

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

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

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

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

> My favorite quote of Dr. Edwin H. Land goes as follows -- "We know all the
> answers -- we just haven't asked the right questions." That is what
> science is
> all about.
>
> The reason your analysis is wrong is because YOU'RE NOT ASKING THE RIGHT
> QUESTIONS.

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