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Experimental Evidence for Dynamic Doppler Shift

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Anonymous
August 14, 2004 8:30:38 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

THE HYPOTHESIS:
Assuming that the equation for the Doppler frequency shift of a source
moving at constant velocity also applies under dynamically changing
velocity conditions, one would expect the propagating sound, that is
produced by a high-frequency source moving dynamically at a low
frequency around a fixed position, to be frequency modulated. One
would further expect that the instantaneous frequency of the
propagating sound would reflect the dynamic low-frequency velocity the
source. If so, the waveform of the fm-demodulated high-frequency
propagating sound, should follow on an instantaneous basis, the
dynamic velocity of the low-frequency velocity of the source.


THE SETUP:
A small circular piezoelectric bimorph, having a resonant frequency of
approximately 10KHz was attached to the 10-lb armature/shaft of a
linear motor. The displacement of the armature/shaft was monitored
by a linear displacement transducer attached to the opposite end of
the armature/shaft. The linear displacement transducer also provided
feedback for the servo amplifier which was driving the linear motor.
Because the linear motor was in a servo loop, the displacement of the
motor followed with reasonable accuracy both sinusoidal and
non-sinusoidal command signals that were applied to the amplifier.
The piezoelectric sound source was driven by a low-distortion
oscillator at 10KHz. The sound emitted by the source was measured by a
microphone at a distance of approximately one foot. The output of the
microphone was amplified, high-pass filtered and applied to a
frequency-to-voltage converter. The output of the
frequency-to-voltage converter was low-pass filtered to reduce the
level of the residual 10KHz carrier, amplified and applied to a signal
averager. The signal averager was triggered by the command signal
that was applied to the linear motor. Averaging was used in order to
remove non-coherent 60Hz that was present in the output of the
demodulator.


THE MOTION OF THE SOUND SOURCE
A triangular command signal having a 50-msec period was applied to the
servo amplifier. A triangular command signal was used in order to
simplify interpretation of the measurement result and to avoid the
phase shift vs time delay ambiguity that would otherwise exist with
fixed frequency sinusoidal excitation. The output of the displacement
transducer was monitored on an oscilloscope and found to be triangular
with rounded corners. The rounding of the corners is due to the
limited closed-bandwidth of the servo. The velocity of the linear
motor was therefore trapezoidal with relatively flat and relatively
long plateaus and relatively short transitions.


THE MEASUREMENT RESULT
The propagating 10KHz signal emitted by the piezo bimorph was applied
to an FFT analyzer in zoom-analysis mode with a resolution bandwidth
of 0.1Hz. When the piezo bimorph was stationary, the propagating
signal picked up by the microphone showed only a single spectral peak
at 10KHz. When the piezo transducer was moving back and forth with a
triangular displacement provided by the linear motor, the propagating
signal received by the microphone contained numerous sidebands which
were indicative of FM modulation. Additionally, the output of the FM
demodulator was observed to be trapezoidal and followed on an
instantaneous basis the velocity of the linear motor and the attached
piezo transducer.


THE CHALLENGE
In science, theory usually follows experimental results. In this case
the experimental result shows that a 10KHz signal applied to a small
piezoelectric source moving back and forth around a fixed position
becomes frequency modulated by the back and forth motion of the
source. The measurement further shows that the received,
FM-demodulated signal follows the instantaneous velocity of the
source. This result is exactly what is expected on the basis of
Doppler frequency shift extrapolated from constant velocity to dynamic
velocity conditions. While some might argue that the observed
FM-like sidebands and the trapezoidal demodulated waveform are the
result of IM distortion, and not Doppler FM, the ball is in their
court. It is now up to them to provide an explanation/analysis
involving an IM producing mechanism in the present experimental setup
that accounts for the present experimental result. Finally, it must
be noted that the purpose of the present measurement was to
demonstrate fundamental phenomenological behavior. The 10KHz carrier
and the 50-msec peridiocity for the displacement of the linear motor
were chosen solely to accommodate the hardware on hand. There is
presently no reason to believe that the outcome of the present
measurement would be different if other carrier frequencies or other
source displacement periodicities or waveshapes were used.
Anonymous
August 14, 2004 8:48:54 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

Thank you, Herr Geist.
Anonymous
August 14, 2004 10:08:49 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

The Ghost wrote:

> THE HYPOTHESIS:
> Assuming that the equation for the Doppler frequency shift of a source
> moving at constant velocity also applies under dynamically changing
> velocity conditions,

And therein is the flaw. Because the driver face is riding
the wave it creates, the distance from the driver to the
detector is not the instantaneous position of its face but
its rest position. That remains constant with a signal that
contains no DC component so that Doppler shift does not occur.


Bob
--

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

A. Einstein
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Anonymous
August 15, 2004 4:45:47 AM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

Bob Cain wrote:

>
>
> The Ghost wrote:
>
>> THE HYPOTHESIS: Assuming that the equation for the Doppler frequency
>> shift of a source
>> moving at constant velocity also applies under dynamically changing
>> velocity conditions,
>
>
> And therein is the flaw. Because the driver face is riding the wave it
> creates, the distance from the driver to the detector is not the
> instantaneous position of its face but its rest position. That remains
> constant with a signal that contains no DC component so that Doppler
> shift does not occur.

C'mon, Gary. As difficult as I know this will be for you, I
know also that you are smart enough to eventually acknowlede
that I'm correct in my final analysis of this if you are
intellectually honest, which I think you are. I won't crow,
I promise. :-)

Interestingly enough, and probably good for your ego, your's
is really the only acknowledgment I care about.


Bob
--

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

A. Einstein
August 15, 2004 9:42:42 AM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

The Ghost wrote:
snip
>
> THE MEASUREMENT RESULT
> The propagating 10KHz signal emitted by the piezo bimorph was applied
> to an FFT analyzer in zoom-analysis mode with a resolution bandwidth
> of 0.1Hz. When the piezo bimorph was stationary, the propagating
> signal picked up by the microphone showed only a single spectral peak
> at 10KHz. When the piezo transducer was moving back and forth with a
> triangular displacement provided by the linear motor, the propagating
> signal received by the microphone contained numerous sidebands which
> were indicative of FM modulation. Additionally, the output of the FM
> demodulator was observed to be trapezoidal and followed on an
> instantaneous basis the velocity of the linear motor and the attached
> piezo transducer.
>
snip

Ghost, I think most people here were not doubting that a Doppler-shift will
occurr, but how audible it is. Maybe you can do another experiment: Move the
piezo-frequency down to 1-2kHz to be in a more sensitive area of the ear.
Then use the modulator at a low frequency like 8Hz, where there is another
sensitive area of the ear, and use a high amplitude of 5cm if that is
possible to get the same speed as a woofer at 80Hz with 5mm excursion.
Can you hear the modulation as a small vibrato?
Could you also quantify your transmission index in the form of frequency
deviation vs. mm/s

--
ciao Ban
Bordighera, Italy
Anonymous
August 15, 2004 3:20:10 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

"The Ghost"
>
>
> THE MOTION OF THE SOUND SOURCE
> A triangular command signal having a 50-msec period was applied to the
> servo amplifier. A triangular command signal was used in order to
> simplify interpretation of the measurement result and to avoid the
> phase shift vs time delay ambiguity that would otherwise exist with
> fixed frequency sinusoidal excitation.


** Time delay variations and the resultant phase shifts are not removed by
this.


> The output of the displacement
> transducer was monitored on an oscilloscope and found to be triangular
> with rounded corners. The rounding of the corners is due to the
> limited closed-bandwidth of the servo. The velocity of the linear
> motor was therefore trapezoidal with relatively flat and relatively
> long plateaus and relatively short transitions.


** Numbers please - what was the velocity ???

In any case this test is not equivalent to the woofer cone situation since
the piezo is clearly moving *through* the air.




............... Phil
Anonymous
August 15, 2004 3:20:11 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

On Sun, 15 Aug 2004 11:20:10 +1000, "Phil Allison"
<philallison@tpg.com.au> wrote:

[snip]
> In any case this test is not equivalent to the woofer cone situation since
>the piezo is clearly moving *through* the air.

What's the woofer cone moving through?

But, unless the woofer or piezo is porous, neither would be moving
through the air, nor would air be moving through them.

If the issue is the difference in the local fluid flow field around
the piezo or the woofer cone, how would that affect the Doppler shift?

Ken Plotkin
Anonymous
August 15, 2004 6:00:51 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

"Ken Plotkin"
"Phil Allison"
>
> [snip]
> > In any case this test is not equivalent to the woofer cone situation
since
> >the piezo is clearly moving *through* the air.
>
> What's the woofer cone moving through?


** It takes a volume of air with it as it pumps - so the same air
molecules remain in contact with the surface ( convection notwithstanding) .

>
> But, unless the woofer or piezo is porous, neither would be moving
> through the air, nor would air be moving through them.
>


** The tiny piezo device is not able to take an air volume with it as it
moves bodily.


> If the issue is the difference in the local fluid flow field around
> the piezo or the woofer cone, how would that affect the Doppler shift?
>


** Dunno - but it is interesting to think about since all the familiar
examples of Doppler shift involve the sound source being moved through the
air and exciting it at different places from moment to moment.






.......... Phil
Anonymous
August 15, 2004 6:07:53 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

On Sun, 15 Aug 2004 14:00:51 +1000, "Phil Allison"
<philallison@tpg.com.au> wrote:


>** It takes a volume of air with it as it pumps - so the same air
>molecules remain in contact with the surface ( convection notwithstanding) .

>** The tiny piezo device is not able to take an air volume with it as it
>moves bodily.

At what point do the laws of physics that apply to the woofer cone
become different for the piezo?
Anonymous
August 15, 2004 6:07:54 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

Ken Plotkin wrote:
> On Sun, 15 Aug 2004 14:00:51 +1000, "Phil Allison"
> <philallison@tpg.com.au> wrote:
>
>
>
>>** It takes a volume of air with it as it pumps - so the same air
>>molecules remain in contact with the surface ( convection notwithstanding) .
>
>
>>** The tiny piezo device is not able to take an air volume with it as it
>>moves bodily.
>
>
> At what point do the laws of physics that apply to the woofer cone
> become different for the piezo?


Perhaps it's related to the efficiency of coupling the LF signal to the
air? At some frequency the air becomes part of the cone's radiating
structure, below that it's not. This would apply the milliHertz vs DC
paradox as well.
Anonymous
August 15, 2004 7:20:52 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

Bob Cain wrote:

>
>
> The Ghost wrote:
>
>> THE HYPOTHESIS: Assuming that the equation for the Doppler frequency
>> shift of a source
>> moving at constant velocity also applies under dynamically changing
>> velocity conditions,
>
>
> And therein is the flaw. Because the driver face is riding the wave it
> creates, the distance from the driver to the detector is not the
> instantaneous position of its face but its rest position. That remains
> constant with a signal that contains no DC component so that Doppler
> shift does not occur.

Another way of saying this is that it is the bulk velocity
at the rest position that propegates as the velocity wave,
with the pressure related in the usual way.

What, then, is the relationship between the surface velocity
of the piston and the bulk velocity of air at the rest
position? If they are proportional, or otherwise related
linearly, then "Doppler distortion" can be relegated to the
dustbin of history. If not, my hat will soon begin eyeing
me warily.


Bob
--

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

A. Einstein
Anonymous
August 15, 2004 9:25:55 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

"The Ghost" <the_ghostbuster@netzero.com> wrote in message
news:b5fb78ba.0408141530.3dd3a5dc@posting.google.com...

> ...the propagating
> signal received by the microphone contained numerous sidebands which
> were indicative of FM modulation.

Redundancy alert!!

You just wrote 'Frequency Modulation modulation'.

OK pedants, fire at will...


'People who can't say what they mean don't mean what they say'


--
'Murphy is my Co-Pilot'

"I won't go into binary counting here. For further information you can
search the Internet, or cut off all but one of your fingers."
-Roger Nichols
Anonymous
August 15, 2004 9:25:56 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

In alt.sci.physics.acoustics,rec.audio.pro, "Natalie Drest"
<mccoeyHAT@netspaceCOAT.net.au> wrote:

>
>"The Ghost" <the_ghostbuster@netzero.com> wrote in message
>news:b5fb78ba.0408141530.3dd3a5dc@posting.google.com...
>
>> ...the propagating
>> signal received by the microphone contained numerous sidebands which
>> were indicative of FM modulation.
>
>Redundancy alert!!
>
>You just wrote 'Frequency Modulation modulation'.
>
>OK pedants, fire at will...

No problem, just don't touch my MIDI interface. And I hang my
pedant on a chain around my neck just like a Real Man... :) 

>
>
>'People who can't say what they mean don't mean what they say'

-----
http://mindspring.com/~benbradley
Anonymous
August 15, 2004 10:01:06 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

On Sun, 15 Aug 2004 12:27:25 -0700, S O'Neill <nospam@nospam.org>
wrote:

>KP> At what point do the laws of physics that apply to the woofer cone
>KP> become different for the piezo?
>
>
>Perhaps it's related to the efficiency of coupling the LF signal to the
>air? At some frequency the air becomes part of the cone's radiating
>structure, below that it's not. This would apply the milliHertz vs DC
>paradox as well.

Ummm...maybe I should have been ruder in my previous post. The notion
that there is a local flow field for the woofer cone but not one for
the piezo driver is ludicrous. They may be different depending on
size and wavelength, but there will be a local flow for both.
Anonymous
August 15, 2004 11:27:16 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

Phil Allison wrote:
> ** It takes a volume of air with it as it pumps - so the same air
> molecules remain in contact with the surface ( convection notwithstanding) .

If you were willing to ride on the cone (take your cowboy hat with
you), or if you could convince a microphone to be your surrogate, then
indeed no frequency shift as heard by you or the mic would occur. To
that extent you are correct. But we live in a relativistic world whether
you care to or not.

The "observer" or the SLM microphone resides in a stationary reference
frame, while the loudspeaker cone moves with respect to that fixed
reference frame. Whether the air moves by the observer and his/her
microphone, it is still clear that the tone heard will increase in pitch
while the cone is advancing in his/her direction, and reduce in pitch
when receding from said observation location; air still or not. Even if
a steady breeze is blowing in any direction, and the distance is less
that 300 feet, the same FM will occur. Now if there are wind *gusts*,
(accelerations; changes of velocity), then the pitch will change
momentarily... Need we scrutinize any further?

Ang. C.
August 16, 2004 3:43:29 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

"Bob Cain" <arcane@arcanemethods.com> wrote in message
news:cfon2s014gp@enews4.newsguy.com...
>
> Another way of saying this is that it is the bulk velocity
> at the rest position that propegates as the velocity wave,
> with the pressure related in the usual way.

Have the terms of discussion changed? I think you originally said that
there cannot be Doppler distortion because the system you were considering
was linear. Gary's experimental setup was linear in the conventional sense
but (of course) produced Doppler distortion. Now it's to do with bulk
velocity.

I don't think it's a good idea to get hung up on definitions of
linearity. Gary's setup produced a form of distortion that you could call
time distortion. This is not a distortion that we usually give a general
name to, although in simple analogue recording systems it is called by
various names depending on the type of speed variation that gives rise to
it. Clearly time distortion will produce frequencies not present in the
original signal, although it is not "non-linear" in the usual sense. I have
to say I can't see why time distortion shouldn't happen in a conventional
speaker setup just as it does in Gary's.

Keep going - I quite enjoy these discussions because it makes me think.

Tony Woolf
Anonymous
August 16, 2004 7:36:04 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

Tony wrote:

> "Bob Cain" <arcane@arcanemethods.com> wrote in message
> news:cfon2s014gp@enews4.newsguy.com...
>
>>Another way of saying this is that it is the bulk velocity
>>at the rest position that propegates as the velocity wave,
>>with the pressure related in the usual way.
>
>
> Have the terms of discussion changed? I think you originally said that
> there cannot be Doppler distortion because the system you were considering
> was linear.

I did and I do. What in said above is part of the means of
proving that. If it is true and the surface velocity of the
piston is transformed linearly to the bulk velocity at the
rest position then linearity of the system is assured.

> Gary's experimental setup was linear in the conventional sense
> but (of course) produced Doppler distortion. Now it's to do with bulk
> velocity.

In this case experiment that does not confirm theory is not
of particular value, especially when there are other factors
that can contribute to the data. We lack such a theory.

The bulk velocity argument is just another way of getting at
the basic principles involved and one that is getting right
down to acoustics fundamentals.

>
> I don't think it's a good idea to get hung up on definitions of
> linearity. Gary's setup produced a form of distortion that you could call
> time distortion. This is not a distortion that we usually give a general
> name to, although in simple analogue recording systems it is called by
> various names depending on the type of speed variation that gives rise to
> it. Clearly time distortion will produce frequencies not present in the
> original signal, although it is not "non-linear" in the usual sense. I have
> to say I can't see why time distortion shouldn't happen in a conventional
> speaker setup just as it does in Gary's.

What I hope to see from Gary is a predictive theory with
rigorous math with which his data can be compared. If it
can be done, I'm pretty sure he can do it.


Bob
--

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

A. Einstein
Anonymous
August 16, 2004 7:51:29 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

Tony wrote:
> Have the terms of discussion changed?

No. I believe that they are incomplete.

Consider another mode, called "modulation", which is not, or may not be
considered to be, 'distortion', and more certainly is intended NOT to be
nonlinear. The two simple cases of modulation are amplitude modulation
and frequency modulation. Can anyone here claim these two perturbations
of a steady signal to be nonlinear? We must settle this question first.

I say that the word "distortion" is too pervasive, and is now loosing
its meaning and relevance. For years, I had heard the term 'frequency
distortion' and thought it infer a nonlinear process. Then I learned
that it was being used ion the audio world merely to reflect the fact
that a pass band was not flat. Now we are using it for frequency
modulation via doppler, and sure enough, some other souls are making the
same nonlinear inference, which is also not true.

> I think you originally said that
> there cannot be Doppler distortion because the system you were considering
> was linear. Gary's experimental setup was linear in the conventional sense
> but (of course) produced Doppler distortion. Now it's to do with bulk
> velocity.

I think this exactly follows my last statements.
>
> I don't think it's a good idea to get hung up on definitions of
> linearity.

Right. Non linearity begins when the transfer function (output/input) of
an entity is not a straight line.
> Gary's setup produced a form of distortion that you could call
> time distortion. This is not a distortion that we usually give a general
> name to, although in simple analogue recording systems it is called by
> various names depending on the type of speed variation that gives rise to
> it. Clearly time distortion will produce frequencies not present in the
> original signal, although it is not "non-linear" in the usual sense.

Right. One indictor is that the side bands are in the immediate vicinity
of the primary (carrier) frequencies. No harmonics, for instance.

> I have
> to say I can't see why time distortion shouldn't happen in a conventional
> speaker setup just as it does in Gary's.

'Time distortion' can be inferred from the doppler phenomenon.

> Keep going - I quite enjoy these discussions because it makes me
> think.

There is a closing line in the stage play
"Teahouse of the August Moon"...

'Pain makes man think,
thought makes man wise,
and wisdom makes life endurable!.'

Ang. C.
Anonymous
August 16, 2004 7:51:30 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

> 'Pain makes man think,
> thought makes man wise,
> and wisdom makes life endurable!.'

Except, of course, for that unendurable pain!

By the way, those lines are a modified version of something from the Greeks.
Anonymous
August 16, 2004 10:20:48 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

"Natalie Drest" <mccoeyHAT@netspaceCOAT.net.au> wrote in message news:<cfn363.

> Redundancy alert!!
> You just wrote 'Frequency Modulation modulation'.

I trust that your thoughtful insight and technologically salient
contribution to this thread didn't create any permanent damage from
neural overload.
Anonymous
August 17, 2004 1:19:00 AM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

Angelo Campanella wrote:

> Tony wrote:
>
>> Have the terms of discussion changed?
>
>
> No. I believe that they are incomplete.
>
> Consider another mode, called "modulation", which is not, or may not be
> considered to be, 'distortion', and more certainly is intended NOT to be
> nonlinear. The two simple cases of modulation are amplitude modulation
> and frequency modulation. Can anyone here claim these two perturbations
> of a steady signal to be nonlinear? We must settle this question first.

Angelo, all modulation is performed by non-linear elements.
The test of whether a system is linear or not is whether
there are frequencies in the output that are not in the
input. If there aren't for any input the system is linear.
If there are for any input it isn't linear. This is just
a vernacular statement of the very definition of linearity.

> Right. Non linearity begins when the transfer function (output/input) of
> an entity is not a straight line.

It's trivial to design a system that has a straight line
transfer function within the limits of measurement if setup
and measurement are done on successive days, or even with
minutes in between, but will distort all to hell if given a
sin wave.

If you have a system that shows a straight line transfer
function regardless of the input, it's not only linear, it
is purely resistive.


Bob
--

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

A. Einstein
Anonymous
August 17, 2004 9:17:53 AM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

Bob Cain wrote:
> Angelo, all modulation is performed by non-linear elements. The test of

It's a matter of semantics for modulation and distortion. Non-linear is
a little more specific.

Such arguments often arise between engineers, physicists and
mathematicians; each having a slightly different view of the physical
and virtual worlds. The only hope is that they be specific and to
elaborate while seeking a common language to get the job done.

arividercci, nonlinearity


Ang. C.
August 17, 2004 12:51:04 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

"Angelo Campanella" <a.campanella@att.net> wrote in message
news:5K4Uc.214645$OB3.105910@bgtnsc05-news.ops.worldnet.att.net...
>
> I say that the word "distortion" is too pervasive, and is now loosing
> its meaning and relevance. For years, I had heard the term 'frequency
> distortion' and thought it infer a nonlinear process. Then I learned
> that it was being used ion the audio world merely to reflect the fact
> that a pass band was not flat. Now we are using it for frequency
> modulation via doppler, and sure enough, some other souls are making the
> same nonlinear inference, which is also not true.

As we have found before in this forum, words ("shabby equipment always
deteriorating") have their limitations . When I was trained as a BBC
engineer about 40 years ago, I was told that distortion was anything that
altered the original sound. The BBC Programme Operations Training Manual
(1962) states that distortion occurs when any change in waveform takes place
between two points in a transmission system. It lists (a) phase distortion
i.e., transmission time varying with frequency, (b) a number of types of
non-linear distortion inlcuding what we would now call dynamic range
compression and (c) attenuation or frequency distortion, caused when the
properties of the system vary with frequency. This is slightly different
from my own training which I think used an even more general definition - it
included hum and noise, as well as wow and flutter. I am not trying to say
that this was "correct", I am just saying that you can't t rely on a precise
meaning of such words without further definition.

Tony Woolf
Anonymous
August 17, 2004 12:51:05 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

"Tony" <news-reply@t-onywoolf.co.uk> wrote in message
news:YFjUc.1727$Xv4.21194796@news-text.cableinet.net
> "Angelo Campanella" <a.campanella@att.net> wrote in message
> news:5K4Uc.214645$OB3.105910@bgtnsc05-news.ops.worldnet.att.net...

>> I say that the word "distortion" is too pervasive, and is now loosing
>> its meaning and relevance.

I would say that distortion has always had a broad meaning.

>>For years, I had heard the term 'frequency
>> distortion' and thought it infer a nonlinear process. Then I learned
>> that it was being used in the audio world merely to reflect the fact
>> that a pass band was not flat.

Yes, this is the well-known linear distortion.

>> Now we are using it for frequency
>> modulation via doppler, and sure enough, some other souls are making
>> the same nonlinear inference, which is also not true.

The definition of distortion given at
http://www.pcavtech.com/techtalk/dist_noise/index.htm is general and
orthodox.

> When I was trained as a BBC
> engineer about 40 years ago, I was told that distortion was anything
> that altered the original sound.

This isn't quite right because noise and interfering signals are quite
different from distortion, but can alter the origional sound.

> The BBC Programme Operations
> Training Manual (1962) states that distortion occurs when any change
> in waveform takes place between two points in a transmission system.

Ignoring noise and interfering signals, this would be about right.

> It lists (a) phase distortion i.e., transmission time varying with
> frequency, (b) a number of types of non-linear distortion inlcuding
> what we would now call dynamic range compression and (c) attenuation
> or frequency distortion, caused when the properties of the system
> vary with frequency.

Nonlinear distortion has a very clear and distinct definition:

"Errors that add tones to the output signal that not present in the input
signal but are related to tones in the input signal are called nonlinear
distortion."

> This is slightly different from my own training
> which I think used an even more general definition - it included hum
> and noise, as well as wow and flutter.

Noise can easily and properly be thought of as being distinct from
distortion, but wow and flutter are FM distortion, and agree the formal
definition of nonlinear distortion. However, they are not caused by the
signal acting on itself. They are a result of the action of an interferring
signal, in this case the uneven rotation of a turntable as seen from the
perspective of the stylus.

> I am not trying to say that
> this was "correct", I am just saying that you can't t rely on a
> precise meaning of such words without further definition.

At this time there appears to be pretty good agreement about the formal
definitions of these terms.
Anonymous
August 17, 2004 1:13:44 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

Tony <news-reply@t-onywoolf.co.uk> wrote:
>This is slightly different
>from my own training which I think used an even more general definition - it
>included hum and noise, as well as wow and flutter. I am not trying to say
>that this was "correct", I am just saying that you can't t rely on a precise
>meaning of such words without further definition.

Sadly, the working definition that I see most often is that "distortion"
is the same thing as "clipping.". And that DRIVES ME UP THE FREAKING WALL.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 17, 2004 10:32:44 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

"The Ghost" <the_ghostbuster@netzero.com> wrote in message
news:b5fb78ba.0408161720.7910a07c@posting.google.com...
> "Natalie Drest" <mccoeyHAT@netspaceCOAT.net.au> wrote in message
news:<cfn363.
>
> > Redundancy alert!!
> > You just wrote 'Frequency Modulation modulation'.
>
> I trust that your thoughtful insight and technologically salient
> contribution to this thread didn't create any permanent damage from
> neural overload.

Your trust is well placed, though your manners aren't up to much I must say.
You ought to have thanked me- I didn't want you to hand in your dissertation
with silly errors in it.
But hey- go right ahead!
Anonymous
August 17, 2004 10:32:45 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

"Natalie Drest" <mccoeyHAT@netspaceCOAT.net.au> wrote in message news:<cfsfre$2r3i$1@otis.netspace.net.au>...

> Your trust is well placed, though your manners aren't up to much I must say.
> You ought to have thanked me- I didn't want you to hand in your dissertation
> with silly errors in it.
> But hey- go right ahead!


I regret having missed your coronation as queen identifier of silly
errors in newsgroup posts. You obviously have a great challenge
ahead of you because most if not all newsgroup posts contain silly
errors of one sort or another. However, unlike you, most readers
focus on substance and ignore those silly errors. If you expect to be
thanked for your input, perhaps you should do the same. Lastly, if
you want to identfy a really silly error, take a look into a mirror.
Anonymous
August 17, 2004 11:01:31 PM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

Bob Cain <arcane@arcanemethods.com> wrote in message news:<cfrcba02nef@enews2.newsguy.com>...
>
> What I hope to see from Gary is a predictive theory with
> rigorous math with which his data can be compared. If it
> can be done, I'm pretty sure he can do it.


One of my favorite business philosophers said something to the effect
that hope long delayed makes the heart sick. Personally, I have found
that to be true. Accordingly, if you are hoping for me to give you
anything other than the time of day, I suggest that start stocking up
on heart medication right now. And in case anyone reading this
doesn't understand where that sort of comment is coming from, I
suggest that they do a google search and educate themselves regarding
the numerous insults that you have bestowed upon me over the last
three years.


You will find the analysis for instantaneous Doppler shift on page 453
in Allan Pierce's book on Acoustics which is published by McGraw-Hill.
You will find further details in the referenced article "The Sound
Field for Singularities in Motion" which was published in the
Proceedings of the Royal Society of London. However, in light of your
track record, I doubt that you will be able to understand the analyses
contained in these works. Furthermore, in light of your gross
ignorance of and your pre-disposed bias against real scientific
thought and analysis, I doubt that you are prepared to accept their
validity.
Anonymous
August 18, 2004 12:05:25 AM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

The Ghost wrote:

> One of my favorite business philosophers said something to the effect
> that hope long delayed makes the heart sick. Personally, I have found
> that to be true. Accordingly, if you are hoping for me to give you
> anything other than the time of day, I suggest that start stocking up
> on heart medication right now. And in case anyone reading this
> doesn't understand where that sort of comment is coming from, I
> suggest that they do a google search and educate themselves regarding
> the numerous insults that you have bestowed upon me over the last
> three years.

Ah, Gary, I just love it when you do that. Yes, I was
hoping you would post the facts if you have them and hoped
the pleasure you would derive from your anticipation of my
discomfort might motivate you. Alas, your pathology has
gifted you with the ability you to see through my simple
foil. Ah, well.

If anyone else has the text Gary so thoughtfully provided as
reference, I would greatly appreciate you posting the
expression or expression which define this "Doppler distortion."


Bob
--

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

A. Einstein
Anonymous
August 18, 2004 1:26:45 AM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

"Arny Krueger"

> Nonlinear distortion has a very clear and distinct definition:
>
> "Errors that add tones to the output signal that not present in the input
> signal but are related to tones in the input signal are called nonlinear
> distortion."
>


** In what context did you find those words ????

Cyclic frequency variations produced by a tape recorder or TT are not
added tones but mechanically induced errors appearing in the output signal
from a storage system.

Phase modulation of a high frequency by a low one and it associated
Doppler shift are errors inherent in air displacement pressure transducers.

When you move someone's words from one context to another - that creates
error as well.

Gotta be careful.



............. Phil
Anonymous
August 18, 2004 1:26:46 AM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:2oe8biF9nv9oU2@uni-berlin.de
> "Arny Krueger"
>
>> Nonlinear distortion has a very clear and distinct definition:
>>
>> "Errors that add tones to the output signal that not present in the
>> input signal but are related to tones in the input signal are called
>> nonlinear distortion."
>>
>
>
> ** In what context did you find those words ????

Read the parts of the post that you deleted, Phil. Or, see below.

> Cyclic frequency variations produced by a tape recorder or TT are not
> added tones but mechanically induced errors appearing in the output
> signal from a storage system.

The spectrum analyzer shows added tones. The same is true of digital audio
equipment jitter.

> Phase modulation of a high frequency by a low one and it associated
> Doppler shift are errors inherent in air displacement pressure
> transducers.

Agreed.

> When you move someone's words from one context to another - that
> creates error as well.

You mean like you just did, Phil? You trashed the context in which the words
were origionally posted, for sure!

BTW, the author of the words above are clearly labelled if you bother to
trace back the provided URL:

"The definition of distortion given at
http://www.pcavtech.com/techtalk/dist_noise/index.htm is general and
orthodox."

> Gotta be careful.

Yes you do, Phil.
Anonymous
August 18, 2004 1:26:46 AM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

Phil Allison <philallison@tpg.com.au> wrote:
>
> Cyclic frequency variations produced by a tape recorder or TT are not
>added tones but mechanically induced errors appearing in the output signal
>from a storage system.

Actually, the sidebands that result from those mechanically-induced errors
are added tones. In typical systems, they are so low displacement that it
is not all that singificant.

> Phase modulation of a high frequency by a low one and it associated
>Doppler shift are errors inherent in air displacement pressure transducers.

Agreed.

BUT, both the case of flutter and the case of doppler modulation are both
examples of FM modulation of the signal; what makes them substantively
different is where the modulating signal is coming from.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
Anonymous
August 18, 2004 2:04:41 AM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

"Arny Krueger"
> "Phil Allison"
> >
> >> Nonlinear distortion has a very clear and distinct definition:
> >>
> >> "Errors that add tones to the output signal that not present in the
> >> input signal but are related to tones in the input signal are called
> >> nonlinear distortion."
> >>
> >
> > ** In what context did you find those words ????
>
> Read the parts of the post that you deleted, Phil. Or, see below.


** I see - the context was in fact your own words.

How deceitful to slyly quote yourself the absent expert.



> > Cyclic frequency variations produced by a tape recorder or TT are not
> > added tones but mechanically induced errors appearing in the output
> > signal from a storage system.
>
> The spectrum analyzer shows added tones. The same is true of digital audio
> equipment jitter.


** Because that is all the poor dumb animal can do.

BTW A tone is a steady frequency - that is the opposite of what wow
is.



> > Phase modulation of a high frequency by a low one and it associated
> > Doppler shift are errors inherent in air displacement pressure
> > transducers.
>
> Agreed.


** So wrong to call "non -linear".


>
> > When you move someone's words from one context to another - that
> > creates error as well.
>
> You mean like you just did, Phil?


** Opinion presented as fact.


> You trashed the context in which the words were origionally posted, for
sure!


** There was no *context* supplied and still is none in sight.



> BTW, the author of the words above are clearly labelled if you bother to
> trace back the provided URL:


** Context is not authorship - plus the author seems to be you.


>
> > Gotta be careful.
>
> Yes you do, Phil.
>


** When dealing with a "born again psychopath" - yes.





............. Phil
Anonymous
August 18, 2004 2:04:42 AM

Archived from groups: alt.sci.physics.acoustics,rec.audio.pro (More info?)

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:2oeailF9k9e9U2@uni-berlin.de
> "Arny Krueger"
>> "Phil Allison"
>>>
>>>> Nonlinear distortion has a very clear and distinct definition:
>>>>
>>>> "Errors that add tones to the output signal that not present in the
>>>> input signal but are related to tones in the input signal are
>>>> called nonlinear distortion."
>>>>
>>>
>>> ** In what context did you find those words ????
>>
>> Read the parts of the post that you deleted, Phil. Or, see below.
>
>
> ** I see - the context was in fact your own words.
>
> How deceitful to slyly quote yourself the absent expert.

Where's the deceit? Is it any kind of a secret around here that PCAVTech is
my web site?

>>> Cyclic frequency variations produced by a tape recorder or TT are
>>> not added tones but mechanically induced errors appearing in the
>>> output signal from a storage system.

>> The spectrum analyzer shows added tones. The same is true of digital
>> audio equipment jitter.

> ** Because that is all the poor dumb animal can do.

Yes, it is bound to tell the truth.

> BTW A tone is a steady frequency - that is the opposite of what wow
> is.

Doooh!

>>> Phase modulation of a high frequency by a low one and it associated
>>> Doppler shift are errors inherent in air displacement pressure
>>> transducers.

>> Agreed.

> ** So wrong to call "non -linear".

In a sense, I agree.

>>> When you move someone's words from one context to another - that
>>> creates error as well.

>> You mean like you just did, Phil?

> ** Opinion presented as fact.

Phil, your heavy-handed editing is a matter of fact, easily found in the
google archive of RAP.

>> You trashed the context in which the words were origionally posted,
>> for sure!

> ** There was no *context* supplied and still is none in sight.

Say what?

>> BTW, the author of the words above are clearly labelled if you
>> bother to trace back the provided URL:

> ** Context is not authorship - plus the author seems to be you.

Is it any kind of a secret around here that PCAVTech is my web site?

>>> Gotta be careful.

>> Yes you do, Phil.

> ** When dealing with a "born again psychopath" - yes.

Yawn.
August 18, 2004 2:04:43 AM

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

Frequency and phase response errors are a form of linear distortion
and in audio work is not generally called "distortion" because no new
frequencies are created.

Frequency Modulation (like that caused by wow and flutter or clock
jitter or Doppler) is a non-linear process and produces new tones
(sidebands) (look up Bessel if you don't belive this) and in this
audio context therefore is a form of non-linear distortion because new
frequencies are created.

In fact the point I was making is that the sidebands produced by
Doppler are identical to those that would be produced by actual
intermodulation distortion and thefore Doppler and IM should sound the
same and I see no problem therefore calling Doppler a form of
distortion.



Mark
Anonymous
August 18, 2004 2:04:44 AM

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

"Mark" <makolber@yahoo.com> wrote in message
news:3367f36e.0408171038.77cedc8f@posting.google.com
> Frequency and phase response errors are a form of linear distortion
> and in audio work is not generally called "distortion" because no new
> frequencies are created.
>
> Frequency Modulation (like that caused by wow and flutter or clock
> jitter or Doppler) is a non-linear process and produces new tones
> (sidebands) (look up Bessel if you don't belive this) and in this
> audio context therefore is a form of non-linear distortion because new
> frequencies are created.
>
> In fact the point I was making is that the sidebands produced by
> Doppler are identical to those that would be produced by actual
> intermodulation distortion and thefore Doppler and IM should sound the
> same and I see no problem therefore calling Doppler a form of
> distortion.

Simply not true.

Common IM is AM distortion, which as several have pointed out produces
sidebands that have equal amplitude and phase.

Doppler, flutter, wowo and clock jitter are FM distortion produce sidebands
differ in terms of phase.
Anonymous
August 18, 2004 2:04:45 AM

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

> Common IM is AM distortion, which as several have pointed out produces
> sidebands that have equal amplitude and phase.

> Doppler, flutter, wowo and clock jitter are FM distortion produce sidebands
> differ in terms of phase.

That "wowo" will really get ya. It got its name when people heard it and said
"Wo-wo! That sounds awful!"

The only difference between AM and weak FM is the phase of the sidebands.
Anonymous
August 18, 2004 2:55:41 PM

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

"Mark"
>
> Frequency and phase response errors are a form of linear distortion
> and in audio work is not generally called "distortion" because no new
> frequencies are created.
>
** Fine.

> Frequency Modulation (like that caused by wow and flutter or clock
> jitter or Doppler) is a non-linear process ....


** Speed variations in the playback of a mechanical storage device are a
linear process.

The output signal contains errors from what is desired - so that is a
"distortion".


> and produces new tones (sidebands)


** A tone infected with wow is not a new tone - it is simply FM of the
old one.


(look up Bessel if you don't belive this) and in this
> audio context therefore is a form of non-linear distortion because new
> frequencies are created.


** Categorise it under the heading "non-linear" if you like, but the
process that creates it is a linear one.


> In fact the point I was making is that the sidebands produced by
> Doppler are identical to those that would be produced by actual
> intermodulation distortion....


** Not identical - the maths shows they are quite different.


> and thefore Doppler and IM should sound the
> same


** No way - never heard a Leslie speaker cabinet in action ???

Now that has audible Doppler shift and it DONT sound like AM one bit.



and I see no problem therefore calling Doppler a form of
> distortion.


** You have come full circle and are now biting your own tail.




............ Phil
Anonymous
August 18, 2004 2:55:42 PM

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

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:2ofno8Fa9b38U1@uni-berlin.de
> "Mark"
>>
>> Frequency and phase response errors are a form of linear distortion
>> and in audio work is not generally called "distortion" because no new
>> frequencies are created.
>>
> ** Fine.
>
>> Frequency Modulation (like that caused by wow and flutter or clock
>> jitter or Doppler) is a non-linear process ....
>
>
> ** Speed variations in the playback of a mechanical storage device
> are a linear process.
>
> The output signal contains errors from what is desired - so that
> is a "distortion".
>
>
>> and produces new tones (sidebands)
>
>
> ** A tone infected with wow is not a new tone - it is simply FM of
> the old one.

Right, but FM causes sidebands.

> (look up Bessel if you don't belive this) and in this
>> audio context therefore is a form of non-linear distortion because
>> new frequencies are created.

Those Bessel functions predict the amplitude of the sidebands, right?

Sidebands around a carrier tone are in fact new tones. If you get the
modulation index up high enough, you can even hear them as separate tones.

> ** Categorise it under the heading "non-linear" if you like, but the
> process that creates it is a linear one.

I wouldn't focus on that linear part, too confusing for newbies. Instead,
say something like "It's not dependent on parameter variation due to the
input signal".

>> In fact the point I was making is that the sidebands produced by
>> Doppler are identical to those that would be produced by actual
>> intermodulation distortion....

> ** Not identical - the maths shows they are quite different.

Agreed, the phase differs.

>> and thefore Doppler and IM should sound the
>> same

> ** No way - never heard a Leslie speaker cabinet in action ???

A way too compex example to draw any conclusions from.

> Now that has audible Doppler shift and it DONT sound like AM one bit.

I'll agree with this.

I did the following experiment:

(1) Create 4 KHz tone peak amplitude -1 dB AM with 50 Hz producing sidebands
@-29 dB

(2) Create 4 KHz tone peak amplitude -1 dB FM with 50 Hz producing sidebands
@-29 dB

No comparison. The FM-modulated tone sounded essentially unmodulated, but
the AM-modulated tone sounded clearly modulated.


>> and I see no problem therefore calling Doppler a form of
>> distortion.


> ** You have come full circle and are now biting your own tail.

Agreed - Doppler distorition is a form of nonlinear distortion.

Doppler differs from other common forms of FM distortion in audio such as
wow, flutter, and jitter; becuase modulating signal is part of the origional
signal. With wow, flutter, and jitter the modulating signal may or may not
be part of the origional signal. With wow and flutter the modulating signal
is usually not part of the origional signal. However, there is a form of FM
distortion in vinyl where the modulating signal is part of the origional
signal. It is geometrically-based and is due to the use of offset tone arms.
August 18, 2004 2:55:43 PM

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

"Arny Krueger" <arnyk@hotpop.com> wrote in
news:9fSdnf8whIpJLr_cRVn-uw@comcast.com:


>> ** You have come full circle and are now biting your own tail.
>
> Agreed - Doppler distorition is a form of nonlinear distortion.
>
> Doppler differs from other common forms of FM distortion in audio such
> as wow, flutter, and jitter; becuase modulating signal is part of the
> origional signal. With wow, flutter, and jitter the modulating signal
> may or may not be part of the origional signal. With wow and flutter
> the modulating signal is usually not part of the origional signal.
> However, there is a form of FM distortion in vinyl where the
> modulating signal is part of the origional signal. It is
> geometrically-based and is due to the use of offset tone arms.
>
>
>


I've been looking at these threads for some time. My take is that you've
really been arguing about FM (or PM), not doppler distortion. By taking two
signals and running them through a speaker, you're going to get both AM and
FM components.

In my opinion, if you're going to find doppler distortion, you're going to
have to use a single tone driven speaker and then run the acoustically
captured result through a discriminator and see if there is a non
harmonically related signal left over. That should be your doppler
distortion component.

-Bruce
Anonymous
August 18, 2004 2:55:44 PM

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

"Bruce" <xxx@yyy.zzz> wrote in message
news:Xns9548E183DB2FBxxxyyyzzz@216.77.188.18
> "Arny Krueger" <arnyk@hotpop.com> wrote in
> news:9fSdnf8whIpJLr_cRVn-uw@comcast.com:
>
>
>>> ** You have come full circle and are now biting your own tail.
>>
>> Agreed - Doppler distortion is a form of nonlinear distortion.
>>
>> Doppler differs from other common forms of FM distortion in audio
>> such as wow, flutter, and jitter; because modulating signal is part
>> of the original signal. With wow, flutter, and jitter the
>> modulating signal may or may not be part of the original signal.
>> With wow and flutter the modulating signal is usually not part of
>> the original signal. However, there is a form of FM distortion in
>> vinyl where the modulating signal is part of the original signal.
>> It is geometrically-based and is due to the use of offset tone arms.

> I've been looking at these threads for some time. My take is that
> you've really been arguing about FM (or PM), not Doppler distortion.

Doppler distortion creates FM distortion.

> By taking two signals and running them through a speaker, you're
> going to get both AM and FM components.

True, but quite old news.

BTW, the AM distortion is not due to Doppler distortion.

> In my opinion, if you're going to find Doppler distortion, you're
> going to have to use a single tone driven speaker and then run the
> acoustically captured result through a discriminator and see if there
> is a non harmonically related signal left over.

You've obviously missed something important. There is no Doppler distortion
with one tone, that is unless you move the speaker or something like that.

> That should be your Doppler distortion component.

No, one tone and a fixed speaker and/or recover won't give you any Doppler
distortion.
August 18, 2004 2:55:45 PM

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

">
> You've obviously missed something important. There is no Doppler distortion
> with one tone, that is unless you move the speaker or something like that.
>
> > That should be your Doppler distortion component.
>
> No, one tone and a fixed speaker and/or recover won't give you any Doppler
> distortion.

Then lets clarify what each of us are trying to say.


We have a speaker cone vibrating at both 50 Hz and 4 kHz.

QUESTION 1
Does the 50 Hz cone vibration produce Doppler shift to the 4 kHz?
I believe yes it does and that is what is shown on the spectrum
analyzer previously.

QUESTION 2
Does the 50 Hz cone vibration produce Doppler shift to the 50 Hz?
I believe no it does not, the 50 Hz cone vibration is producing the 50
Hz wave and as far as the 50 Hz wave is concerned there is no
additional movement. In any case, this is a very small effect and not
the question I believe most of us are discussing. I believe most of
us are addressing question #1.

I think it would be helpful in the discussion to clarify which of
these two questions you are discussing.

Also regarding the sidebands, if the modulating frequency (50 Hz in
this example) is very low like 1 Hz then the sidebands are 1 Hz above
and below the carrier and cannot be resolved separately. In this case
you will hear the modulation, AM as a change in loudness and FM as a
change in pitch wow :-).
However, if the modulation frequency is high, say 1 kHz, then the new
sidebands are far removed and can be resolved separately by the ear.
In this case you hears the sidebands as additional tones and in this
case I believe the AM and FM would sound almost the same. You simply
hear the additional sidebands as additional tones.

At 50 Hz, I don't know if they would be resolved (by the ear)or not.
The spectrum analyzer does resolve them.

The key issue is the modulation frequency, are the new sidebands
removed sufficiently to be resolved by the ear or not. The spectrum
analyzer works the same way, it depends on the resolution bandwidth
relative to the spacing of the sidebands.

Mark
Anonymous
August 18, 2004 2:55:46 PM

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

"Mark" <makolber@yahoo.com> wrote in message
news:3367f36e.0408180526.60211f1e@posting.google.com
> ">
>> You've obviously missed something important. There is no Doppler
>> distortion with one tone, that is unless you move the speaker or
>> something like that.
>>
>>> That should be your Doppler distortion component.
>>
>> No, one tone and a fixed speaker and/or recover won't give you any
>> Doppler distortion.
>
> Then lets clarify what each of us are trying to say.
>
>
> We have a speaker cone vibrating at both 50 Hz and 4 kHz.
>
> QUESTION 1
> Does the 50 Hz cone vibration produce Doppler shift to the 4 kHz?
> I believe yes it does and that is what is shown on the spectrum
> analyzer previously.
>
> QUESTION 2
> Does the 50 Hz cone vibration produce Doppler shift to the 50 Hz?
> I believe no it does not, the 50 Hz cone vibration is producing the 50
> Hz wave and as far as the 50 Hz wave is concerned there is no
> additional movement. In any case, this is a very small effect and not
> the question I believe most of us are discussing. I believe most of
> us are addressing question #1.
>
> I think it would be helpful in the discussion to clarify which of
> these two questions you are discussing.

The first one.

> Also regarding the sidebands, if the modulating frequency (50 Hz in
> this example) is very low like 1 Hz then the sidebands are 1 Hz above
> and below the carrier and cannot be resolved separately.

By instruments?

Yes you can resolve it with test equipment. I've clearly resolved waves as
close together as 1/3 Hz, and could go further, it's just that this is the
lowest frequency common in audio (1/33.333 rpm)

By the ear?


Yes you can resolve it with test equipment, if the modulation is strong
enough. It is heard as "roughness". This is a well-known psychoacoustics
term that makes a lot of subjective sense when you hear it.

>In this case you will hear the modulation, AM as a change in loudness and
>FM as a
> change in pitch wow :-).

At really low modulating frequencies, yes.

> However, if the modulation frequency is high, say 1 kHz, then the new
> sidebands are far removed and can be resolved separately by the ear.

Not really, they are masked. You hear it as roughness.

> In this case you hears the sidebands as additional tones and in this
> case I believe the AM and FM would sound almost the same.

I just did an experiment with a 4 KHz carrier and 50 Hz modulation, with the
same height sidebands and either AM of FM modulation (about 26 dB down). The
sidebands had very similar levels. The AM modulation was clearly audible,
and the FM was very hard to discern.

> You simply hear the additional sidebands as additional tones.

Only if displaced far enough from the carrier to be unmasked.

> At 50 Hz, I don't know if they would be resolved (by the ear)or not.

See previous practical example. Depends on the kind of modulation. The ear
is more sensitive to low frequency FM, and so I'd suspect that if I dropped
the modulating frequency to 1 Hz, the FM would be more likely to be audible.

> The spectrum analyzer does resolve them.

Agreed, if you have the right parameters.

> The key issue is the modulation frequency, are the new sidebands
> removed sufficiently to be resolved by the ear or not.

Separation from the carrier is not required for audibility. There are kinda
like two modes of hearing of modulation, that which is spectrally masked,
and that which is not.

> The spectrum
> analyzer works the same way, it depends on the resolution bandwidth
> relative to the spacing of the sidebands.

IME, modern spectrum analyzers outperform the human ear in terms of raw
analysis, to a ridiculously large extent.
Anonymous
August 18, 2004 3:55:18 PM

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

"Arny Krueger"
> "Phil Allison"
"Mark"

> >
> >> Frequency Modulation (like that caused by wow and flutter or clock
> >> jitter or Doppler) is a non-linear process ....
> >
> >
> > ** Speed variations in the playback of a mechanical storage device
> > are a linear process.
> >
> > The output signal contains errors from what is desired - so that
> > is a "distortion".
> >
> >
> >> and produces new tones (sidebands)
> >
> >
> > ** A tone infected with wow is not a new tone - it is simply FM of
> > the old one.
>
> Right, but FM causes sidebands.


** Circular thinking.

>
> > ** Categorise it under the heading "non-linear" if you like, but the
> > process that creates it is a linear one.
>
> I wouldn't focus on that linear part, too confusing for newbies.


** Not near as confusing as all the other tripe posted here.


>
> >> In fact the point I was making is that the sidebands produced by
> >> Doppler are identical to those that would be produced by actual
> >> intermodulation distortion....
>
> > ** Not identical - the maths shows they are quite different.
>
> Agreed, the phase differs.


** And the frequency spectrum. AM of a frequency produces only two new
frequencies ( sum and diff ) - while FM produces a *whole bunch*.


>
> I did the following experiment:
>
> (1) Create 4 KHz tone peak amplitude -1 dB AM with 50 Hz producing
sidebands
> @-29 dB
>
> (2) Create 4 KHz tone peak amplitude -1 dB FM with 50 Hz producing
sidebands
> @-29 dB
>
> No comparison. The FM-modulated tone sounded essentially unmodulated, but
> the AM-modulated tone sounded clearly modulated.
>


** The ear's sensitivity phase modulation at an audio frequency is clearly
quite poor.





............ Phil
Anonymous
August 18, 2004 3:55:19 PM

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

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:2ofr80Fa5qmlU1@uni-berlin.de
> "Arny Krueger"
>> "Phil Allison"
> "Mark"

>>>> In fact the point I was making is that the sidebands produced by
>>>> Doppler are identical to those that would be produced by actual
>>>> intermodulation distortion....

>>> ** Not identical - the maths shows they are quite different.

>> Agreed, the phase differs.

> ** And the frequency spectrum. AM of a frequency produces only two
> new frequencies ( sum and diff ) - while FM produces a *whole
> bunch*.

Right, but for modest Modulation Indices, there is only one pair of
sidebands that has a hope of being audible. In the experiment below, the
second set of sidebands were 62 dB down. And the first pair weren't very
audible!

>> I did the following experiment:
>>
>> (1) Create 4 KHz tone peak amplitude -1 dB AM with 50 Hz producing
>> sidebands @-29 dB
>>
>> (2) Create 4 KHz tone peak amplitude -1 dB FM with 50 Hz producing
>> sidebands @-29 dB

>> No comparison. The FM-modulated tone sounded essentially
>> unmodulated, but the AM-modulated tone sounded clearly modulated.

> ** The ear's sensitivity phase modulation at an audio frequency is
> clearly quite poor.

How about that?

;-)
Anonymous
August 18, 2004 5:18:59 PM

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

"Arny Krueger"
> "Phil Allison"
> >
> > ** And the frequency spectrum. AM of a frequency produces only two
> > new frequencies ( sum and diff ) - while FM produces a *whole
> > bunch*.
>
> Right, but for modest Modulation Indices, there is only one pair of
> sidebands that has a hope of being audible.


** Time for someone put the term "Modulation Index" into perspective:

1. The MI for broadcast FM with full modulation at 20Hz is 3750.

2. The MI for broadcast FM with full modulation at 1 kHz is 75.

3. The MI for narrow band FM with full modulation at 50 Hz is 100.

4. The MI for a typical woofer at X-max at 40 Hz / 4000kHz is less than 1.


So - the case of the woofer is one with a ** very low ** MI.


Also, the MI figure corresponds to the phase modulation depth in radians (1
radian = 57 degrees).

In the case of a woofer, that depth is less than 57 degrees or 1/6 of a
cycle.





............. Phil
August 19, 2004 12:21:44 AM

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

"Arny Krueger" <arnyk@hotpop.com> wrote in
news:BfOdneZUAboBXr_cRVn-sQ@comcast.com:

> "Bruce" <xxx@yyy.zzz> wrote in message
> news:Xns9548E183DB2FBxxxyyyzzz@216.77.188.18
>> "Arny Krueger" <arnyk@hotpop.com> wrote in
>> news:9fSdnf8whIpJLr_cRVn-uw@comcast.com:
>> I've been looking at these threads for some time. My take is that
>> you've really been arguing about FM (or PM), not Doppler distortion.
>
> Doppler distortion creates FM distortion.

Hi Arny,

Well, since we all agree that Doppler Effect is the variance in frequency
of a tone(The moving train whistle story), which would be by another
definition Frequency Modulation(FM) of that tone by some other influence,
right? Then as I see it, this what is being described as far as I can tell.
This isn't what I would term, and maybe others here, as distortion.
>
>> By taking two signals and running them through a speaker, you're
>> going to get both AM and FM components.
>
> True, but quite old news.

Okay, but there now seems to be a contradiction. If you already know you're
going to get Amplitude and Frequency Modulation components by feeding two
signals of different frequencies into a common driver, what is there to
argue about?

It seems to me that there are some who want to call these modulation
components distortion. I don't see this as being correct in the definitions
I am familiar with. (Maybe this is the case with others here as well)

>
> BTW, the AM distortion is not due to Doppler distortion.

Never said it was.

>
>> In my opinion, if you're going to find Doppler distortion, you're
>> going to have to use a single tone driven speaker and then run the
>> acoustically captured result through a discriminator and see if there
>> is a non harmonically related signal left over.
>
> You've obviously missed something important. There is no Doppler
> distortion with one tone, that is unless you move the speaker or
> something like that.
>
>> That should be your Doppler distortion component.
>
> No, one tone and a fixed speaker and/or recover won't give you any
> Doppler distortion.
>
>

Then I can't see how you have "Doppler Distortion" by the speaker. It is
the speaker causing distortion we're after, no? You have either Doppler
Effect, or Frequency Modulation by the methodologies I've seen so far
employed, which isn't distortion caused soley by the speaker, but an
expected phenomena.

I still maintain that if it is being said that a speaker causes "doppler
distortion" then it will have to do it on it's own, not by adding multiple
waveforms together already knowing that this will result in both AM and FM
components. Either the speaker cone with a single tone is moving in such a
way that it changes the fundamental frequency of the tone being fed into
it, or it isn't. My own conclusion is that Doppler Distortion has not been
demonstrated, but that Doppler Effect or Frequency Modulation components
are present as expected.

As I said earlier, it looks like some fundamental terms have been mixed
together which is causing confusion in the various arguments as I have
followed them. Everyone is not on the same page. Anyway, I certainly hope
you all get this topic sorted out. I've gotten more than my 0.02 in and
since I don't think I can help(or cause harm) in anyway further, I will
return to the sidelines. Good luck.

-Bruce
Anonymous
August 19, 2004 12:21:45 AM

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

"Bruce" <xxx@yyy.zzz> wrote in message
news:Xns9549A68704F29xxxyyyzzz@216.77.188.18
> "Arny Krueger" <arnyk@hotpop.com> wrote in
> news:BfOdneZUAboBXr_cRVn-sQ@comcast.com:
>
>> "Bruce" <xxx@yyy.zzz> wrote in message
>> news:Xns9548E183DB2FBxxxyyyzzz@216.77.188.18
>>> "Arny Krueger" <arnyk@hotpop.com> wrote in
>>> news:9fSdnf8whIpJLr_cRVn-uw@comcast.com:
>>> I've been looking at these threads for some time. My take is that
>>> you've really been arguing about FM (or PM), not Doppler distortion.
>>
>> Doppler distortion creates FM distortion.

> Well, since we all agree that Doppler Effect is the variance in
> frequency of a tone(The moving train whistle story), which would be
> by another definition Frequency Modulation(FM) of that tone by some
> other influence, right?

Agreed.

>Then as I see it, this what is being
> described as far as I can tell. This isn't what I would term, and
> maybe others here, as distortion.

It's clearly a form of FM distortion. FM distortion is clearly nonlinear
distortion.


>>> By taking two signals and running them through a speaker, you're
>>> going to get both AM and FM components.

>> True, but quite old news.

> Okay, but there now seems to be a contradiction. If you already know
> you're going to get Amplitude and Frequency Modulation components by
> feeding two signals of different frequencies into a common driver,
> what is there to argue about?

Lots of things, such as the relative audibility of each. You see, it might
be possible to improve the AM distortion of a driver by making a more linear
design, using better materials, etc. But FM distortion is essentially due to
geometry. If want a certain SPL out of a speaker with a certain sized
diaphragm, you are going to have a certain amount of FM distortion and there
is nothing you can do about it.


> It seems to me that there are some who want to call these modulation
> components distortion.

That is accepted practice.

>I don't see this as being correct in the
> definitions I am familiar with. (Maybe this is the case with others
> here as well)

>> BTW, the AM distortion is not due to Doppler distortion.
>
> Never said it was.

Good

>>> In my opinion, if you're going to find Doppler distortion, you're
>>> going to have to use a single tone driven speaker and then run the
>>> acoustically captured result through a discriminator and see if
>>> there is a non harmonically related signal left over.

>> You've obviously missed something important. There is no Doppler
>> distortion with one tone, that is unless you move the speaker or
>> something like that.

>>> That should be your Doppler distortion component.

>> No, one tone and a fixed speaker and/or recover won't give you any
>> Doppler distortion.

> Then I can't see how you have "Doppler Distortion" by the speaker. It
> is the speaker causing distortion we're after, no?

The distortion does not exist until the sound reaches the receiver.

>You have either
> Doppler Effect, or Frequency Modulation by the methodologies I've
> seen so far employed, which isn't distortion caused soley by the
> speaker, but an expected phenomena.

Agreed.

> I still maintain that if it is being said that a speaker causes
> "doppler distortion" then it will have to do it on it's own, not by
> adding multiple waveforms together already knowing that this will
> result in both AM and FM components.

In a certain light I'm willing to say that the speaker does not make the
distortion.

>Either the speaker cone with a
> single tone is moving in such a way that it changes the fundamental
> frequency of the tone being fed into it, or it isn't. My own
> conclusion is that Doppler Distortion has not been demonstrated, but
> that Doppler Effect or Frequency Modulation components are present as
> expected.

Doppler distortion is very real.
Anonymous
August 19, 2004 12:21:46 AM

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

Arny Krueger wrote:


> The distortion does not exist until the sound reaches the receiver.

Arny! That's about the silliest thing I've ever heard from
someone that is techno-savvy.


Bob
--

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

A. Einstein
August 19, 2004 1:10:57 AM

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

"Arny Krueger" <arnyk@hotpop.com> wrote in
news:476dnaFondfJWb7cRVn-jA@comcast.com:

>

>> Then I can't see how you have "Doppler Distortion" by the speaker. It
>> is the speaker causing distortion we're after, no?
>
> The distortion does not exist until the sound reaches the receiver.

I'm sorry Arny, but this one is too good to pass up....

To me this is like saying a bear doesn't s**t in the woods until you step
in it.

-Bruce
!