Doppler Distortion - Case closed - go away

[Goofball_star_dot_etal]

http://www.wareing.dircon.co.uk/images/Bingo.jpg

[Bob Cain]

Goofball_star_dot_etal wrote:

> http://www.wareing.dircon.co.uk/images/Bingo.jpg

Yeah, but some words would be nice explaining what it says. :-)


Bob
--

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

A. Einstein

[Bob Cain]

Goofball_star_dot_etal wrote:

> http://www.wareing.dircon.co.uk/images/Bingo.jpg

Yeah, but some words would be nice explaining what it says. :-)


Bob
--

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

A. Einstein

[Bob Cain]

Goofball_star_dot_etal wrote:

> http://www.wareing.dircon.co.uk/images/Bingo.jpg

Ya know, an experiment that would put this to bed is a
really rigid flat piston and an interferometer that could
measure it's position or velocity as a function of time and
then compare that with the pressure wave produced under
these two tone test conditions as measured by a really low
dostortion mic.

If the sidebands are signifigantly different, there's
Doppler distortion. If not, it's history.


Bob
--

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

A. Einstein

[Bob Cain]

Goofball_star_dot_etal wrote:

> http://www.wareing.dircon.co.uk/images/Bingo.jpg

Ya know, an experiment that would put this to bed is a
really rigid flat piston and an interferometer that could
measure it's position or velocity as a function of time and
then compare that with the pressure wave produced under
these two tone test conditions as measured by a really low
dostortion mic.

If the sidebands are signifigantly different, there's
Doppler distortion. If not, it's history.


Bob
--

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

A. Einstein

[Goofball_star_dot_etal]

On Fri, 13 Aug 2004 02:23:19 -0700, Bob Cain
> wrote:

>
>
>Goofball_star_dot_etal wrote:
>
>> http://www.wareing.dircon.co.uk/images/Bingo.jpg
>
>Ya know, an experiment that would put this to bed is a
>really rigid flat piston and an interferometer that could
>measure it's position or velocity as a function of time and
>then compare that with the pressure wave produced under
>these two tone test conditions as measured by a really low
>dostortion mic.
>
>If the sidebands are signifigantly different, there's
>Doppler distortion. If not, it's history.
>

Since a very idealised speaker produces an accoustic pressure
proportional to acceleration then an accelerometer output recorded
simultaneously with a mic output on each of two stereo channels and
processed in exactly the same way should reveal differences caused by
the air path ( and things that are not ideal which are not common to
both channels. . )
It is a pity you did not claim the available points on r.a.t when you
had the chance.

[Goofball_star_dot_etal]

On Fri, 13 Aug 2004 02:23:19 -0700, Bob Cain
> wrote:

>
>
>Goofball_star_dot_etal wrote:
>
>> http://www.wareing.dircon.co.uk/images/Bingo.jpg
>
>Ya know, an experiment that would put this to bed is a
>really rigid flat piston and an interferometer that could
>measure it's position or velocity as a function of time and
>then compare that with the pressure wave produced under
>these two tone test conditions as measured by a really low
>dostortion mic.
>
>If the sidebands are signifigantly different, there's
>Doppler distortion. If not, it's history.
>

Since a very idealised speaker produces an accoustic pressure
proportional to acceleration then an accelerometer output recorded
simultaneously with a mic output on each of two stereo channels and
processed in exactly the same way should reveal differences caused by
the air path ( and things that are not ideal which are not common to
both channels. . )
It is a pity you did not claim the available points on r.a.t when you
had the chance.

[Goofball_star_dot_etal]

On Fri, 13 Aug 2004 02:15:34 -0700, Bob Cain
> wrote:

>
>
>Goofball_star_dot_etal wrote:
>
>> http://www.wareing.dircon.co.uk/images/Bingo.jpg
>
>Yeah, but some words would be nice explaining what it says. :-)
>
>

Well as one of my bosses used to say to his students: "Never mind your
conclusions, show me the data"

I can tell you what it is, though - It is what it says.

Now some background:
The raw data is that posted by Arny on his web site.
It was processed by my home-made software which demodulates AM/PM and
AM quite independently and does much else besides.

I calculated the cone displacment for each input voltage on the basis
(a crude estimate) of a peak linear deviation of 1/16 inch @ 10 V.
I calculated what fraction of a wavelength at the carrier frequency
(4025 Hz) this was and multiplied by 2 Pi radians. This was
plotted on the X-axis.

My software has a "local oscillator" which was set to 4025 Hz.
It outputs the phase and frequency difference between the input
waveform and 4025 Hz reference and the ampltude of the input. It does
this by using quadrature detection.

The detected phase, frequency and amplitude modulations can then be
analysed by FFT.

The y-axis shows the 50 Hz bin of the phase modulation FFT converted
to phase deviation (radians)

Do you think that it is a coincidence that X and Y are directly
proportional and show signs of wanting to be *equal*

[Goofball_star_dot_etal]

On Fri, 13 Aug 2004 02:15:34 -0700, Bob Cain
> wrote:

>
>
>Goofball_star_dot_etal wrote:
>
>> http://www.wareing.dircon.co.uk/images/Bingo.jpg
>
>Yeah, but some words would be nice explaining what it says. :-)
>
>

Well as one of my bosses used to say to his students: "Never mind your
conclusions, show me the data"

I can tell you what it is, though - It is what it says.

Now some background:
The raw data is that posted by Arny on his web site.
It was processed by my home-made software which demodulates AM/PM and
AM quite independently and does much else besides.

I calculated the cone displacment for each input voltage on the basis
(a crude estimate) of a peak linear deviation of 1/16 inch @ 10 V.
I calculated what fraction of a wavelength at the carrier frequency
(4025 Hz) this was and multiplied by 2 Pi radians. This was
plotted on the X-axis.

My software has a "local oscillator" which was set to 4025 Hz.
It outputs the phase and frequency difference between the input
waveform and 4025 Hz reference and the ampltude of the input. It does
this by using quadrature detection.

The detected phase, frequency and amplitude modulations can then be
analysed by FFT.

The y-axis shows the 50 Hz bin of the phase modulation FFT converted
to phase deviation (radians)

Do you think that it is a coincidence that X and Y are directly
proportional and show signs of wanting to be *equal*

[Goofball_star_dot_etal]

On Fri, 13 Aug 2004 10:45:10 GMT,
(Goofball_star_dot_etal) wrote:

There are some old examples of the use of my software to measure
turnables still left here:

http://www.wareing77.plus.com/turntable-web.htm

[Goofball_star_dot_etal]

On Fri, 13 Aug 2004 10:45:10 GMT,
(Goofball_star_dot_etal) wrote:

There are some old examples of the use of my software to measure
turnables still left here:

http://www.wareing77.plus.com/turntable-web.htm

[Bob Cain]

Goofball_star_dot_etal wrote:

> Do you think that it is a coincidence that X and Y are directly
> proportional and show signs of wanting to be *equal*

Sorry, but your description still leaves me wondering what
you have shown. Maybe it's just me, but I don't get it.


Bob
--

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

A. Einstein

[Bob Cain]

Goofball_star_dot_etal wrote:

> Do you think that it is a coincidence that X and Y are directly
> proportional and show signs of wanting to be *equal*

Sorry, but your description still leaves me wondering what
you have shown. Maybe it's just me, but I don't get it.


Bob
--

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

A. Einstein

[Bob Cain]

Goofball_star_dot_etal wrote:

> On Fri, 13 Aug 2004 02:23:19 -0700, Bob Cain
> > wrote:
>
>>Ya know, an experiment that would put this to bed is a
>>really rigid flat piston and an interferometer that could
>>measure it's position or velocity as a function of time and
>>then compare that with the pressure wave produced under
>>these two tone test conditions as measured by a really low
>>dostortion mic.
>>
>>If the sidebands are signifigantly different, there's
>>Doppler distortion. If not, it's history.
>
> Goofball wrote:
>
> Since a very idealised speaker produces an accoustic pressure
> proportional to acceleration

I've claimed, and I am pretty sure proven by a reciprocity
argument, that it's proportional to piston velocity. If you
missed it I'll repeat it. If there's any hole in it I'd
really like to know what it is, exactly.

The reason I like to think of a flat, rigid piston rather
than a cone is that a cone has a geometry, even if rigid and
not carrying a traveling acoustic wave from center to
surround, that obfuscates the problem because it is
imparting it's energy to the air in a way that is smeared in
space on the axis of propegation and will thus be smeared in
time. I don't think this has any consequences that impact
the usual "Doppler distortion" argument but it muddies the
picture for linear analysis.

> It is a pity you did not claim the available points on r.a.t when you
> had the chance.

Huh? Perhaps the discussion should have been left there but
I don't know those folks. I do know there are specific
people here capable of fully understanding the issue and
finding holes in my thesis.


Bob
--

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

A. Einstein

[Bob Cain]

Goofball_star_dot_etal wrote:

> On Fri, 13 Aug 2004 02:23:19 -0700, Bob Cain
> > wrote:
>
>>Ya know, an experiment that would put this to bed is a
>>really rigid flat piston and an interferometer that could
>>measure it's position or velocity as a function of time and
>>then compare that with the pressure wave produced under
>>these two tone test conditions as measured by a really low
>>dostortion mic.
>>
>>If the sidebands are signifigantly different, there's
>>Doppler distortion. If not, it's history.
>
> Goofball wrote:
>
> Since a very idealised speaker produces an accoustic pressure
> proportional to acceleration

I've claimed, and I am pretty sure proven by a reciprocity
argument, that it's proportional to piston velocity. If you
missed it I'll repeat it. If there's any hole in it I'd
really like to know what it is, exactly.

The reason I like to think of a flat, rigid piston rather
than a cone is that a cone has a geometry, even if rigid and
not carrying a traveling acoustic wave from center to
surround, that obfuscates the problem because it is
imparting it's energy to the air in a way that is smeared in
space on the axis of propegation and will thus be smeared in
time. I don't think this has any consequences that impact
the usual "Doppler distortion" argument but it muddies the
picture for linear analysis.

> It is a pity you did not claim the available points on r.a.t when you
> had the chance.

Huh? Perhaps the discussion should have been left there but
I don't know those folks. I do know there are specific
people here capable of fully understanding the issue and
finding holes in my thesis.


Bob
--

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

A. Einstein

[Goofball_star_dot_etal]

On Fri, 13 Aug 2004 14:51:18 -0700, Bob Cain
> wrote:

>
>
>Goofball_star_dot_etal wrote:
>
>> On Fri, 13 Aug 2004 02:23:19 -0700, Bob Cain
>> > wrote:
>>
>>>Ya know, an experiment that would put this to bed is a
>>>really rigid flat piston and an interferometer that could
>>>measure it's position or velocity as a function of time and
>>>then compare that with the pressure wave produced under
>>>these two tone test conditions as measured by a really low
>>>dostortion mic.
>>>
>>>If the sidebands are signifigantly different, there's
>>>Doppler distortion. If not, it's history.
> >
> > Goofball wrote:
>>
>> Since a very idealised speaker produces an accoustic pressure
>> proportional to acceleration
>
>I've claimed, and I am pretty sure proven by a reciprocity
>argument, that it's proportional to piston velocity. If you
>missed it I'll repeat it. If there's any hole in it I'd
>really like to know what it is, exactly.
>
It is proportional to displacement, velocity, acceleration, jerk (the
rate of change of acceleration, note) at a particular frequency. If
the frequency is allowed to change it is proportional to acceleration,
I think. Read what Svante wrote, I find him to be quite reliable(TM)
in these matters.

I quote:
"
p=U*rho0*w/(4*pi*r)

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


>The reason I like to think of a flat, rigid piston rather
>than a cone is that a cone has a geometry, even if rigid and
>not carrying a traveling acoustic wave from center to
>surround, that obfuscates the problem because it is
>imparting it's energy to the air in a way that is smeared in
>space on the axis of propegation and will thus be smeared in
>time. I don't think this has any consequences that impact
>the usual "Doppler distortion" argument but it muddies the
>picture for linear analysis.
>
>> It is a pity you did not claim the available points on r.a.t when you
>> had the chance.
>
>Huh? Perhaps the discussion should have been left there but
>I don't know those folks. I do know there are specific
>people here capable of fully understanding the issue and
>finding holes in my thesis.
>
>
>Bob
>--
>
>"Things should be described as simply as possible, but no
>simpler."
>
> A. Einstein

[Goofball_star_dot_etal]

On Fri, 13 Aug 2004 14:51:18 -0700, Bob Cain
> wrote:

>
>
>Goofball_star_dot_etal wrote:
>
>> On Fri, 13 Aug 2004 02:23:19 -0700, Bob Cain
>> > wrote:
>>
>>>Ya know, an experiment that would put this to bed is a
>>>really rigid flat piston and an interferometer that could
>>>measure it's position or velocity as a function of time and
>>>then compare that with the pressure wave produced under
>>>these two tone test conditions as measured by a really low
>>>dostortion mic.
>>>
>>>If the sidebands are signifigantly different, there's
>>>Doppler distortion. If not, it's history.
> >
> > Goofball wrote:
>>
>> Since a very idealised speaker produces an accoustic pressure
>> proportional to acceleration
>
>I've claimed, and I am pretty sure proven by a reciprocity
>argument, that it's proportional to piston velocity. If you
>missed it I'll repeat it. If there's any hole in it I'd
>really like to know what it is, exactly.
>
It is proportional to displacement, velocity, acceleration, jerk (the
rate of change of acceleration, note) at a particular frequency. If
the frequency is allowed to change it is proportional to acceleration,
I think. Read what Svante wrote, I find him to be quite reliable(TM)
in these matters.

I quote:
"
p=U*rho0*w/(4*pi*r)

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


>The reason I like to think of a flat, rigid piston rather
>than a cone is that a cone has a geometry, even if rigid and
>not carrying a traveling acoustic wave from center to
>surround, that obfuscates the problem because it is
>imparting it's energy to the air in a way that is smeared in
>space on the axis of propegation and will thus be smeared in
>time. I don't think this has any consequences that impact
>the usual "Doppler distortion" argument but it muddies the
>picture for linear analysis.
>
>> It is a pity you did not claim the available points on r.a.t when you
>> had the chance.
>
>Huh? Perhaps the discussion should have been left there but
>I don't know those folks. I do know there are specific
>people here capable of fully understanding the issue and
>finding holes in my thesis.
>
>
>Bob
>--
>
>"Things should be described as simply as possible, but no
>simpler."
>
> A. Einstein

[Goofball_star_dot_etal]

On Fri, 13 Aug 2004 14:33:51 -0700, Bob Cain
> wrote:

>
>
>Goofball_star_dot_etal wrote:
>
>> Do you think that it is a coincidence that X and Y are directly
>> proportional and show signs of wanting to be *equal*
>
>Sorry, but your description still leaves me wondering what
>you have shown. Maybe it's just me, but I don't get it.
>

Not the Y=X bit, I hope.
or that frequency is the rate of change of phase.
So which particular bit?
It could be stated: Phase difference in = Phase difference out, which
sounds intuitively correct in this situation.

[Goofball_star_dot_etal]

On Fri, 13 Aug 2004 14:33:51 -0700, Bob Cain
> wrote:

>
>
>Goofball_star_dot_etal wrote:
>
>> Do you think that it is a coincidence that X and Y are directly
>> proportional and show signs of wanting to be *equal*
>
>Sorry, but your description still leaves me wondering what
>you have shown. Maybe it's just me, but I don't get it.
>

Not the Y=X bit, I hope.
or that frequency is the rate of change of phase.
So which particular bit?
It could be stated: Phase difference in = Phase difference out, which
sounds intuitively correct in this situation.

[Bob Cain]

Goofball_star_dot_etal wrote:

> Read what Svante wrote, I find him to be quite reliable(TM)
> in these matters.

Yeah, he's good.

>
> I quote:
> "
> p=U*rho0*w/(4*pi*r)
>
> where U is the volume flow in m3/s (=surface*velocity), rho0=1.2kg/m3,
> w is the angular frequency, and r is the distance.
> After some thinking about this equation, one can realise that sound
> pressure is roportional to the piston *acceleration* (comes from w*U,
> ie derivative of the flow).
> "

This seems to be a calculation for a spherical wave
emanating from a point source. What's he say about a plane
wave emanating from a piston?


Bob
--

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

A. Einstein

[Bob Cain]

Goofball_star_dot_etal wrote:

> Read what Svante wrote, I find him to be quite reliable(TM)
> in these matters.

Yeah, he's good.

>
> I quote:
> "
> p=U*rho0*w/(4*pi*r)
>
> where U is the volume flow in m3/s (=surface*velocity), rho0=1.2kg/m3,
> w is the angular frequency, and r is the distance.
> After some thinking about this equation, one can realise that sound
> pressure is roportional to the piston *acceleration* (comes from w*U,
> ie derivative of the flow).
> "

This seems to be a calculation for a spherical wave
emanating from a point source. What's he say about a plane
wave emanating from a piston?


Bob
--

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

A. Einstein

[Goofball_star_dot_etal]

On Fri, 13 Aug 2004 16:57:00 -0700, Bob Cain
> wrote:

>
>
>Goofball_star_dot_etal wrote:
>
>> Read what Svante wrote, I find him to be quite reliable(TM)
>> in these matters.
>
>Yeah, he's good.
>
>>
>> I quote:
>> "
>> p=U*rho0*w/(4*pi*r)
>>
>> where U is the volume flow in m3/s (=surface*velocity), rho0=1.2kg/m3,
>> w is the angular frequency, and r is the distance.
>> After some thinking about this equation, one can realise that sound
>> pressure is roportional to the piston *acceleration* (comes from w*U,
>> ie derivative of the flow).
>> "
>
>This seems to be a calculation for a spherical wave
>emanating from a point source.

Yes, a speaker (idealised). What most of us are thinking about and
experimenting upon.

> What's he say about a plane
>wave emanating from a piston?
>

He says you are being very stubborn!

John's dad say "Try dimensional analysis on it. No can loose T-1
willy-nilly"


>
>Bob
>--
>
>"Things should be described as simply as possible, but no
>simpler."
>
> A. Einstein

[Goofball_star_dot_etal]

On Fri, 13 Aug 2004 16:57:00 -0700, Bob Cain
> wrote:

>
>
>Goofball_star_dot_etal wrote:
>
>> Read what Svante wrote, I find him to be quite reliable(TM)
>> in these matters.
>
>Yeah, he's good.
>
>>
>> I quote:
>> "
>> p=U*rho0*w/(4*pi*r)
>>
>> where U is the volume flow in m3/s (=surface*velocity), rho0=1.2kg/m3,
>> w is the angular frequency, and r is the distance.
>> After some thinking about this equation, one can realise that sound
>> pressure is roportional to the piston *acceleration* (comes from w*U,
>> ie derivative of the flow).
>> "
>
>This seems to be a calculation for a spherical wave
>emanating from a point source.

Yes, a speaker (idealised). What most of us are thinking about and
experimenting upon.

> What's he say about a plane
>wave emanating from a piston?
>

He says you are being very stubborn!

John's dad say "Try dimensional analysis on it. No can loose T-1
willy-nilly"


>
>Bob
>--
>
>"Things should be described as simply as possible, but no
>simpler."
>
> A. Einstein

[Bob Cain]

Goofball_star_dot_etal wrote:

> John's dad say "Try dimensional analysis on it. No can loose T-1
> willy-nilly"

Good idea. Piston velocity is in m/sec. So is air velocity
at any point in a planar wave, call it V. For the planar
wave case, air velocity is related to air pressure by,

P = V * Ra

at all points in the wave. P is N/m^2, V is m/sec and Ra is
N*sec/m^3.

Both the planar velocity and pressure at any point of the
wave are in constant proportion to the piston velocity at
some time in the past.

Is that stubborn or correct? :-)


Bob
--

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

A. Einstein

[Bob Cain]

Goofball_star_dot_etal wrote:

> John's dad say "Try dimensional analysis on it. No can loose T-1
> willy-nilly"

Good idea. Piston velocity is in m/sec. So is air velocity
at any point in a planar wave, call it V. For the planar
wave case, air velocity is related to air pressure by,

P = V * Ra

at all points in the wave. P is N/m^2, V is m/sec and Ra is
N*sec/m^3.

Both the planar velocity and pressure at any point of the
wave are in constant proportion to the piston velocity at
some time in the past.

Is that stubborn or correct? :-)


Bob
--

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

A. Einstein

[Goofball_star_dot_etal]

On Fri, 13 Aug 2004 19:50:22 -0700, Bob Cain
> wrote:

>
>
>Goofball_star_dot_etal wrote:
>
>> John's dad say "Try dimensional analysis on it. No can loose T-1
>> willy-nilly"
>
>Good idea. Piston velocity is in m/sec. So is air velocity
>at any point in a planar wave, call it V. For the planar
>wave case, air velocity is related to air pressure by,
>
> P = V * Ra
>
>at all points in the wave. P is N/m^2, V is m/sec and Ra is
>N*sec/m^3.
>
>Both the planar velocity and pressure at any point of the
>wave are in constant proportion to the piston velocity at
>some time in the past.
>
>Is that stubborn or correct? :-)
>
>

Stubborn and correct.

I have already said that at a *fixed* frequency you are correct. I
want to a formula similar to that given by Svante that contains a term
for frequency that is dimensionally correct. I meant dimensions as in
[MLT] but MKS units will do.

[Bob Cain]

Goofball_star_dot_etal wrote:

> On Fri, 13 Aug 2004 19:50:22 -0700, Bob Cain
> > wrote:
>
>
>>
>>Goofball_star_dot_etal wrote:
>>
>>
>>>John's dad say "Try dimensional analysis on it. No can loose T-1
>>>willy-nilly"
>>
>>Good idea. Piston velocity is in m/sec. So is air velocity
>>at any point in a planar wave, call it V. For the planar
>>wave case, air velocity is related to air pressure by,
>>
>> P = V * Ra
>>
>>at all points in the wave. P is N/m^2, V is m/sec and Ra is
>>N*sec/m^3.
>>
>>Both the planar velocity and pressure at any point of the
>>wave are in constant proportion to the piston velocity at
>>some time in the past.
>>
>>Is that stubborn or correct? :-)
>>
>>
>
>
> Stubborn and correct.
>
> I have already said that at a *fixed* frequency you are correct. I
> want to a formula similar to that given by Svante that contains a term
> for frequency that is dimensionally correct. I meant dimensions as in
> [MLT] but MKS units will do.

What I wrote is true regardless of the signal. Don't matter
what it looks like. If that's not so, I challenge you to
carefully show why.


Bob
--

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

A. Einstein