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



Randy Yates wrote:


This is in every physics book
and dozens if not hundreds of web sites. To terminate this drivel, I'll
type it in for you here.

The perceived frequency, or Doppler frequency, fd, of a frequency f due
to a relative velocity v between source and observer is given as

fd = f*c/(c + v),

Randy, that equation is only defined for a static v.


So if you start changing v, the doppler effect stops until you
leave v alone for a while? How does the doppler effect know to stop
and start up again?

I didn't say it stops, it just isn't described by that
formula any more. The Doppler effect doesn't know anything.
It is just produced in differing amounts in different
situations.


Seriously (or you can answer the above question seriously if you
like), do you have any reference for the equation being defined only
for v being static?

Not really. That's just the assumption wherever it is
presented. As an example of why an expression that contains
static values won't generally remain valid when simply
substituting a dynamic one, consider a black box containing
some arbitrary network of R, L anc C elements, distributed
and lumped, linear and non-linear, which connect two inputs
to one output.

If we hold one of those inputs X constant and characterize
the output by applying dynamic signals at input Y, then
change the value of the X input to another constant value
and again characterize the output, and repeat this with
enough different values on the constant input we will, in
general, be able to write down an expression that relates
output to input under those conditions. If now instead of
holding the input X constant we apply a time varying signal,
will the characterization we developed describe what the
output will do? Consider what would happen if there were a
parallel RC in series with X before going elsewhere in the
network.

The expression given for Doppler shift is the consequence of
keeping v constant and cannot be generalized to the dynamic
case by substitution. In the general dynamic case it will
be a whole lot more complicated and geometry dependant.
Depending on the geometry it will only be approximated by
the given expression even in the static case. It is really
only generally valid for a point source emitter and receiver
in an unbounded free space filled with nothing but air.


Bob
--

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

A. Einstein

Bob Cain wrote in message ...
fd = f*c/(c + v),

Randy, that equation is only defined for a static v.

You say that with such authority, but you most certainly don't have
the authority required to make such a bold assertion. Can you
provide a reference to the technical literature to support such a
claim? The answer is no, because no such reference exists. The fact
of the matter is that your assertion is nothing more than a personal
belief, which you have accepted without questioning its validity.
Had you looked into it, as I have, you would have discovered that the
equation applies under both constant velocity and dynamic velocity
conditions. You will find the derivation in Allan Pierce's book
entitled "Acoustics: An Introduction to Its Physical Principles and
Applications." In connection with the derivation, Allan Pierce states
"The result holds regardless of the detailed time history of the
trajectory. The Doppler-shifted frequency at a given time and
position is affected only by the source's velocity and frequency at
the instant of generation of the wavelet currently being received.
The source does not have to be traveling with constant velocity or in
a straight line for the equation to apply."

Bob, I've said this many times before and I am going to say it again.
Your level of ignorance never ceases to amaze me.

The Ghost wrote:

You will find the derivation in Allan Pierce's book
entitled "Acoustics: An Introduction to Its Physical Principles and
Applications."

Thanks for the reference. Do you happen to know of one that
derives this and which costs somewhat less that $200 used?


Bob
--

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

A. Einstein

On Sun, 22 Aug 2004 18:28:15 -0700, Bob Cain
wrote:



The Ghost wrote:

You will find the derivation in Allan Pierce's book
entitled "Acoustics: An Introduction to Its Physical Principles and
Applications."

Thanks for the reference. Do you happen to know of one that
derives this and which costs somewhat less that $200 used?

I have no idea what a used copy of Allan's book costs, but new it's
$39. Plus $5 shipping to US locations.

$30 (plus shipping) if you can find an ASA member willing to buy it
for you.

"Bob Cain" wrote in message
...


The Ghost wrote:

You will find the derivation in Allan Pierce's book
entitled "Acoustics: An Introduction to Its Physical Principles and
Applications."

Thanks for the reference. Do you happen to know of one that
derives this and which costs somewhat less that $200 used?

Try http://www.allbookstores.com. I saw that same price on Amazon myself.
Apparently it can be had much cheaper.

In article ,
Bob Cain wrote:

The Ghost wrote:

You will find the derivation in Allan Pierce's book
entitled "Acoustics: An Introduction to Its Physical Principles and
Applications."

Thanks for the reference. Do you happen to know of one that
derives this and which costs somewhat less that $200 used?


Bob


http://asa.aip.org/publications.html#pub05

--
Herb Singleton

Sound & Vibration Measurements
http://www.cross-spectrum.com

Ken Plotkin wrote:

On Sun, 22 Aug 2004 18:28:15 -0700, Bob Cain
wrote:



The Ghost wrote:


You will find the derivation in Allan Pierce's book
entitled "Acoustics: An Introduction to Its Physical Principles and
Applications."

Thanks for the reference. Do you happen to know of one that
derives this and which costs somewhat less that $200 used?


I have no idea what a used copy of Allan's book costs, but new it's
$39. Plus $5 shipping to US locations.

$30 (plus shipping) if you can find an ASA member willing to buy it
for you.

Hmmm, I went to Amazon:

http://www.amazon.com/exec/obidos/AS...212126-4296736

and it shows no new purchase price (out of print) and only a
used one at $193.81. I guess that's the wrong place to
look, eh? If I can find it for $39, it's as good as on order.


Bob
--

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

A. Einstein

Jim Carr wrote:

Try http://www.allbookstores.com. I saw that same price on Amazon myself.
Apparently it can be had much cheaper.

Yes. Found it cheaper through AllBookstores and now have it
on order. At least I hope so. Seems unavailable most
places and the one I'm trying (ClassBook) will let me know
tomorrow of its availability

The general unavailability might be the reasons for the
incredible Amazon used price.

Sokolich so seldom offers any information at all that I'm
wondering if he doesn't know about an availability problem.
Nah, now I'm getting as paranoid as he is. :-)


Thanks,

Bob
--

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

A. Einstein

"Bob Cain" wrote in message

The Ghost wrote:

You will find the derivation in Allan Pierce's book
entitled "Acoustics: An Introduction to Its Physical Principles and
Applications."

Thanks for the reference. Do you happen to know of one that
derives this and which costs somewhat less that $200 used?

http://www.walmart.com/catalog/produ...28 2995418457

$35.10



http://www.audioxpress.com/bksprods/books/bkac2.htm

price $52.95

On Sun, 22 Aug 2004 23:58:52 -0400, "Arny Krueger"
wrote:


http://www.walmart.com/catalog/produ...28 2995418457

$35.10

Out of stock.


http://www.audioxpress.com/bksprods/books/bkac2.htm

price $52.95

Higher than list price.

"Randy Yates" wrote in message
...
Bob Cain writes:

With all this sturm and drang no one has yet produced a mathematical
expression for the sound pressure at some chosen distance from a
velocity controled piston in a tube (to keep the situation as simple
as possible) given a signal containing the sum of some chosen pair of
frequencies at a chosen relative magnitude. Odd, that. Sounds simple
enough.

You know Bob, you are an irritating ****. This is in every physics book
and dozens if not hundreds of web sites. To terminate this drivel, I'll
type it in for you here.

The perceived frequency, or Doppler frequency, fd, of a frequency f due
to a relative velocity v between source and observer is given as

fd = f*c/(c + v),

where c is the speed of the medium (about 1100 ft/second for sound at
reasonable temperatures at sea level).

The instantaneous velocity v(t) of a speaker cone that is reproducing
a sine wave A*sin(2*pi*fl*t) at frequency fl (f low) and at an excursion
of A (meters, inches or whatever) is

v(t) = A*2*pi*fl*cos(2*pi*fl*t).

Put these two facts together and you get the dynamic doppler shift
in a speaker:

fd = f*c/(c + A*2*pi*fl*cos(2*pi*fl*t)).

Of course units have to match, but that's up to the person applying
this equation.

Now what????

How come no one has replied to this logic (or illogic, as the case may
be:-)):
"Here's another way of looking at it, putting a sound wave through a hole
in the wall can't produce Doppler shift, no matter how many tones are in the
waveform, and a speaker is effectively an artificial hole in the wall, in
that the effective sound source isn't the speaker any more than it is the
hole in the wall. Does anyone here think that if you stretched a thin
diaphragm over a hole in a soundproof wall and had a band playing behind it,
the diaphragm would cause Doppler Distortion? The speaker, provided it isn't
exceeding its linear limits, is effectively exactly the same thing for all
practical purposes. Instead of being driven by the sound source in the other
room, it's driven by the electrical equivalent of the sound source in the
other room. Can any of you provide an explanation of how an acoustic wave
driving a diaphragm and passing the soundwave
through it is in any way different than the diaphragm being driven by a
motor being supplied with the exact electrical analog of that acoustic wave?
And by that I mean that the difference will be such that the electrically
driven one will produce Doppler distortion while the acoustically driven one
doesn't."
It seems to me that it boils down to the above situation, if the diaphragm
covering the hole in the wall driven directly by the acoustic wave in the
other room doesn't produce Doppler shift, then the diaphragm being driven by
the exactly equivalent electrical wave won't either. Since the diaphragm
over the hole is moving exactly like the acoustic wave coming through the
hole, I don't see how any form of Doppler shift could be introduced, as
obviously, the hole itself won't introduce Doppler shift. Note, I'm
referring only to Doppler shift, not the lowpass effect of the hole, the
inertia of the diaphragms, etc, which may affect the sound, but will have
absolutely nothing to do with Doppler shift.

"Randy Yates" wrote in message
...
Mark Simonetti writes:

The distortions you are talking about in this thread are comparitively
small, please correct me if I'm wrong. That being the case, I was
basically stating that you often find people are not even bothered
about the larger distortions from sub standard systems, and that I
felt it is unfortunate.

What are these "larger" distortions you are referring to? Seems to
me, as I read someone else state here recently, that the typical
high-end audio freak laments issues that are several orders of
magnitude below something like Doppler distortion in speakers. Not
that Doppler distortion is the largest problem facing sound reproduction,
but comparitively, it seems to be much more worthy of our attention.

If Doppler distortion actually exists in speakers...:-)

Porky wrote:

"Here's another way of looking at it, putting a sound wave through a hole
in the wall can't produce Doppler shift, no matter how many tones are in the
waveform, and a speaker is effectively an artificial hole in the wall, in
that the effective sound source isn't the speaker any more than it is the
hole in the wall. Does anyone here think that if you stretched a thin
diaphragm over a hole in a soundproof wall and had a band playing behind it,
the diaphragm would cause Doppler Distortion?

I like that! It evokes the reciprocity argument I've used
and that nobody seems to like, but in a different and more
realistic configuration. Sorry, Mike, I've been too busy to
give your prior presentation of this a good look (actually
recording and producing some local talent, and I do mean
talent.) So what's wrong with this, anyone?

I realize that Gary Sokolich could dispel it in a moment,
given his authority, but likely won't. Odd, that.

It seems to me that it boils down to the above situation, if the diaphragm
covering the hole in the wall driven directly by the acoustic wave in the
other room doesn't produce Doppler shift, then the diaphragm being driven by
the exactly equivalent electrical wave won't either.

And if it does, someone please explain why. The only
possible answer that I can think of is that it is physically
impossible to generate something in the other room that
isn't Doppler distorted. Is that what is believed?

All sound, it seems then is Doppler distorted. Odd, that. :-)


Bob
--

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

A. Einstein

"Ken Plotkin" wrote in message

On Sun, 22 Aug 2004 23:58:52 -0400, "Arny Krueger"
wrote:


http://www.walmart.com/catalog/produ...28 2995418457

$35.10

Out of stock.

http://www.audioxpress.com/bksprods/books/bkac2.htm

price $52.95

Higher than list price.

Do you want to get the book for an affordable price, or do you want to make
a deal?

This book exudes a strong odor of "out of print".

That means that you look at $52.95, contemplate Amazon's ca. $200 asking
price, and do what you've got to do.

Do you want to get the book for an affordable price,
or do you want to make a deal?
This book exudes a strong odor of "out of print". That
means that you look at $52.95, contemplate Amazon's
ca. $200 asking price, and do what you've got to do.

Exactly! Borrow if from a library and photocopy it!

"Porky" wrote in message
...

other room. Can any of you provide an explanation of how an acoustic wave
driving a diaphragm and passing the soundwave
through it is in any way different than the diaphragm being driven by a
motor being supplied with the exact electrical analog of that acoustic
wave?

In the case of a speaker electrical energy moves a coil which pushes and
pulls a diaphragm in order to compress and rareify air in order to create a
sound wave.

In your example the energy from the sound wave hits the *molecules* of the
diaphragm and passes through at whatever speed of sound is within that
material. The energy passes through that material by hitting air molecules.
It does not force the diaphragm to compress and rareify the air to create a
sound wave.

The former passes sound energy through. The latter creates it via a
different mechanism. At least that's how this undeducated mope sees it.

Can any of you provide an explanation of how an acoustic wave
driving a diaphragm and passing the sound wave through it is
in any way different than the diaphragm being driven by a motor
being supplied with the exact electrical analog of that acoustic
wave?

There is no difference (with one exception, given below).

In the 1980 JAES article explaining the design and development of the QUAD
ESL-63 speaker system, Peter Walker makes this point explicitly -- the sound
impinging the diaphragm sets it in motion, and that motion, in turn, moves the
air on the other side. Mechanical energy IS the energy of motion; it cannot
magically "pass through" the diaphragm without moving it.

The one difference is that a voice coil would drive the diaphragm at only one
point. The ESL-63 is electrostatic, and therefore driven over most of its
surface.

My Stereophile article about the ESL-63 in the SCES report for the year in which
it was introduced explains this in more detail.

alt.sci.physics.acoustics removed, not sure that I have permission to
post the 'please don't crosspost over here' email I got.

On Sun, 22 Aug 2004 20:43:41 -0700, Bob Cain
wrote:



Jim Carr wrote:

Try http://www.allbookstores.com. I saw that same price on Amazon myself.
Apparently it can be had much cheaper.

Yes. Found it cheaper through AllBookstores and now have it
on order.

Which one? I see 1981 ed. for $47.95 and a 1989 ed. for $35.
Clicking on that I get he
http://www.allbookstores.com/book/compare/0883186128
where two of seven sites say it's not available. Who knows how many of
the other have "NOS" or are sold out and the database entry not
updated.

At least I hope so. Seems unavailable most
places and the one I'm trying (ClassBook) will let me know
tomorrow of its availability

The general unavailability might be the reasons for the
incredible Amazon used price.

I see three used copies through bookfinder.com, $95, $150 and $193.
It definitely appears to be hard-to-find and in demand.

Sokolich so seldom offers any information at all that I'm
wondering if he doesn't know about an availability problem.
Nah, now I'm getting as paranoid as he is. :-)


Thanks,

Bob

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

Porky wrote:

If Doppler distortion actually exists in speakers...:-)

It exists, not in speakers but in what follows.


Bob
--

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

A. Einstein

William Sommerwerck wrote:

Can any of you provide an explanation of how an acoustic wave
driving a diaphragm and passing the sound wave through it is
in any way different than the diaphragm being driven by a motor
being supplied with the exact electrical analog of that acoustic
wave?


There is no difference (with one exception, given below).

In the 1980 JAES article explaining the design and development of the QUAD
ESL-63 speaker system, Peter Walker makes this point explicitly -- the sound
impinging the diaphragm sets it in motion, and that motion, in turn, moves the
air on the other side. Mechanical energy IS the energy of motion; it cannot
magically "pass through" the diaphragm without moving it.

William, do you see that this argues against Doppler
distortion being a phenomenon that occurs because of some
wierd mixing at the piston/air interface which makes the
motion that is imparted there intrinsically distorted? The
ESL is a very good piston.

Put one in a teminated tube, for example, and no Doppler
distortion will be generated.

Under conditions of a linear velocity/pressure relationship
in the air, Doppler distortion is something that happens in
the air gradually. Along any ray, it is developed as a
function of the divergence of the frequency dependant
coupling from equal and flat. In the limit of the actual
piston/air interface it goes to zero.


The one difference is that a voice coil would drive the diaphragm at only one
point. The ESL-63 is electrostatic, and therefore driven over most of its
surface.

That's a big difference that is really important but not to
Doppler distortion.


Bob
--

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

A. Einstein

Bob Cain wrote:



Jim Carr wrote:

Try http://www.allbookstores.com. I saw that same price on Amazon myself.
Apparently it can be had much cheaper.


Yes. Found it cheaper through AllBookstores and now have it on order.
At least I hope so. Seems unavailable most places and the one I'm
trying (ClassBook) will let me know tomorrow of its availability

Unavailable. Will try ASA tomorrow.

You too may be able to get upwards of $200 for your copy. :-)


Bob
--

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

A. Einstein

On Mon, 23 Aug 2004 07:25:43 -0400, "Arny Krueger"
wrote:


Do you want to get the book for an affordable price, or do you want to make
a deal?

This book exudes a strong odor of "out of print".

That means that you look at $52.95, contemplate Amazon's ca. $200 asking
price, and do what you've got to do.

I already have a copy, which I bought new for $25.

As has been mentioned a couple of times, the book is available from
ASA for $30 (members) or $39 (non-members) and a link was provided
several posts back.

Ken Plotkin

Bob Cain writes:

Bob Cain wrote:

Jim Carr wrote:

Try http://www.allbookstores.com. I saw that same price on Amazon myself.
Apparently it can be had much cheaper.
Yes. Found it cheaper through AllBookstores and now have it on
order. At least I hope so. Seems unavailable most places and the
one I'm trying (ClassBook) will let me know tomorrow of its
availability

Unavailable. Will try ASA tomorrow.

You too may be able to get upwards of $200 for your copy. :-)

Sure makes it convenient for you to ignore information contradicting
your beliefs, eh Bob?
--
% Randy Yates % "Though you ride on the wheels of tomorrow,
%% Fuquay-Varina, NC % you still wander the fields of your
%%% 919-577-9882 % sorrow."
%%%% % '21st Century Man', *Time*, ELO
http://home.earthlink.net/~yatescr

Randy Yates wrote:

Bob Cain writes:


Bob Cain wrote:


Jim Carr wrote:


Try http://www.allbookstores.com. I saw that same price on Amazon myself.
Apparently it can be had much cheaper.

Yes. Found it cheaper through AllBookstores and now have it on
order. At least I hope so. Seems unavailable most places and the
one I'm trying (ClassBook) will let me know tomorrow of its
availability

Unavailable. Will try ASA tomorrow.

You too may be able to get upwards of $200 for your copy. :-)


Sure makes it convenient for you to ignore information contradicting
your beliefs, eh Bob?

What the **** are you talking about? After finding several
"sources" from which it was not available and a couple that
said it was out of print, I ordered the book yesterday (used
or new) from one that indicated availability and received
the cancellation today. Tomorrow I call ASA to see if they
have it because it was too late to call today when I got the
cancellation. Make sure your mind is loaded before shooting
off your ****ing mouth, cowboy. You're starting to **** me
off and that isn't easy or fun for anyone.

I'd really like to know what has made you so damned snarky
and antagonsitic toward me. Is this the way you always
handle technical disagreement? Seems you've been indulging
in Sokolich's poison.


Bob
--

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

A. Einstein

On Mon, 23 Aug 2004 19:13:32 -0700, Bob Cain
wrote:

[snip]
I'd really like to know what has made you so damned snarky
and antagonsitic toward me. Is this the way you always

Bob, you seem to have a knack for drawing that out.

handle technical disagreement? Seems you've been indulging
in Sokolich's poison.

Poison? I've enjoyed Gary's posts for quite a while. Technical
content is as close to 100% as anyone ever gets - if you ever disagree
with him, you've got to ask yourself what you're missing. His humor
often has me rolling on the floor laughing.

Yeah, discussing personalities is OT, but I'd hate to see Gary get
tired of posting here.

Ken Plotkin

Ken Plotkin writes:

On Mon, 23 Aug 2004 19:13:32 -0700, Bob Cain
wrote:

[snip]
I'd really like to know what has made you so damned snarky
and antagonsitic toward me. Is this the way you always

Bob, you seem to have a knack for drawing that out.

handle technical disagreement? Seems you've been indulging
in Sokolich's poison.

Poison? I've enjoyed Gary's posts for quite a while. Technical
content is as close to 100% as anyone ever gets - if you ever disagree
with him, you've got to ask yourself what you're missing. His humor
often has me rolling on the floor laughing.

Yeah, discussing personalities is OT, but I'd hate to see Gary get
tired of posting here.

Thanks Ken, but my name is Randy!

(:
--
% Randy Yates % "Rollin' and riding and slippin' and
%% Fuquay-Varina, NC % sliding, it's magic."
%%% 919-577-9882 %
%%%% % 'Living' Thing', *A New World Record*, ELO
http://home.earthlink.net/~yatescr

Wow. There *IS* blood flowing to his brain.

--RY

Bob Cain writes:

Randy Yates wrote:

Bob Cain writes:

Bob Cain wrote:


Jim Carr wrote:


Try http://www.allbookstores.com. I saw that same price on Amazon myself.
Apparently it can be had much cheaper.

Yes. Found it cheaper through AllBookstores and now have it on
order. At least I hope so. Seems unavailable most places and the
one I'm trying (ClassBook) will let me know tomorrow of its
availability

Unavailable. Will try ASA tomorrow.

You too may be able to get upwards of $200 for your copy. :-)
Sure makes it convenient for you to ignore information contradicting
your beliefs, eh Bob?

What the **** are you talking about? After finding several "sources"
from which it was not available and a couple that said it was out of
print, I ordered the book yesterday (used or new) from one that
indicated availability and received the cancellation today. Tomorrow
I call ASA to see if they have it because it was too late to call
today when I got the cancellation. Make sure your mind is loaded
before shooting off your ****ing mouth, cowboy. You're starting to
**** me off and that isn't easy or fun for anyone.

I'd really like to know what has made you so damned snarky and
antagonsitic toward me. Is this the way you always handle technical
disagreement? Seems you've been indulging in Sokolich's poison.


Bob
--

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

A. Einstein

--
% Randy Yates % "Though you ride on the wheels of tomorrow,
%% Fuquay-Varina, NC % you still wander the fields of your
%%% 919-577-9882 % sorrow."
%%%% % '21st Century Man', *Time*, ELO
http://home.earthlink.net/~yatescr

PS: Bob, if it makes you feel any better, I'd have a beer
with you, no matter what you think about Doppler! I hope
you can take this along the avenue of laughing at yourself.

(Course it'd be different if we were laughing at me...)

--RY

Randy Yates writes:

Wow. There *IS* blood flowing to his brain.

--RY

Bob Cain writes:

Randy Yates wrote:

Bob Cain writes:

Bob Cain wrote:


Jim Carr wrote:


Try http://www.allbookstores.com. I saw that same price on Amazon myself.
Apparently it can be had much cheaper.

Yes. Found it cheaper through AllBookstores and now have it on
order. At least I hope so. Seems unavailable most places and the
one I'm trying (ClassBook) will let me know tomorrow of its
availability

Unavailable. Will try ASA tomorrow.

You too may be able to get upwards of $200 for your copy. :-)
Sure makes it convenient for you to ignore information contradicting
your beliefs, eh Bob?

What the **** are you talking about? After finding several "sources"
from which it was not available and a couple that said it was out of
print, I ordered the book yesterday (used or new) from one that
indicated availability and received the cancellation today. Tomorrow
I call ASA to see if they have it because it was too late to call
today when I got the cancellation. Make sure your mind is loaded
before shooting off your ****ing mouth, cowboy. You're starting to
**** me off and that isn't easy or fun for anyone.

I'd really like to know what has made you so damned snarky and
antagonsitic toward me. Is this the way you always handle technical
disagreement? Seems you've been indulging in Sokolich's poison.


Bob
--

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

A. Einstein

--
% Randy Yates % "Though you ride on the wheels of tomorrow,
%% Fuquay-Varina, NC % you still wander the fields of your
%%% 919-577-9882 % sorrow."
%%%% % '21st Century Man', *Time*, ELO
http://home.earthlink.net/~yatescr

--
% Randy Yates % "Rollin' and riding and slippin' and
%% Fuquay-Varina, NC % sliding, it's magic."
%%% 919-577-9882 %
%%%% % 'Living' Thing', *A New World Record*, ELO
http://home.earthlink.net/~yatescr

"The Ghost" wrote in message
m...
"Porky" wrote in message
...

Methinks The Ghost has a compulsive need to repeat everything three
times.
Maybe he labors under the misapprehension that repeating a falsehood
enough
will make it true.

Methinks Porky has pig fat for brains.


....And methinks The Ghost has protoplasmic porcine paskat for brains.
(I had to resort to Finnish to keep the alliteration going:-))
BTW, no point in replying to this because you've been *plonked*

"Jim Carr" wrote in message
news:rOmWc.8997$L94.5165@fed1read07...
"Porky" wrote in message
...

other room. Can any of you provide an explanation of how an acoustic
wave
driving a diaphragm and passing the soundwave
through it is in any way different than the diaphragm being driven by a
motor being supplied with the exact electrical analog of that acoustic
wave?

In the case of a speaker electrical energy moves a coil which pushes and
pulls a diaphragm in order to compress and rareify air in order to create
a
sound wave.

In your example the energy from the sound wave hits the *molecules* of the
diaphragm and passes through at whatever speed of sound is within that
material. The energy passes through that material by hitting air
molecules.
It does not force the diaphragm to compress and rareify the air to create
a
sound wave.

The former passes sound energy through. The latter creates it via a
different mechanism. At least that's how this undeducated mope sees it.

Jim, have you ever seen a speaker with a passive radiator? In fact the
diphragm both is driven by the acoustic wave and allows some sound to pass
through it, but what if the the diaphragm were soundproof" If it were low
enough in mass, you'd still hear sound through it, and if it were massless,
you'd hear all the sound. The question then becomes, does the diapragm
generate Doppler distortion because it is driven by the acoustic wave,
especially at the lower frequencies.

"William Sommerwerck" wrote in message
...
Can any of you provide an explanation of how an acoustic wave
driving a diaphragm and passing the sound wave through it is
in any way different than the diaphragm being driven by a motor
being supplied with the exact electrical analog of that acoustic
wave?

There is no difference (with one exception, given below).

In the 1980 JAES article explaining the design and development of the QUAD
ESL-63 speaker system, Peter Walker makes this point explicitly -- the
sound
impinging the diaphragm sets it in motion, and that motion, in turn, moves
the
air on the other side. Mechanical energy IS the energy of motion; it
cannot
magically "pass through" the diaphragm without moving it.

The one difference is that a voice coil would drive the diaphragm at only
one
point. The ESL-63 is electrostatic, and therefore driven over most of its
surface.

My Stereophile article about the ESL-63 in the SCES report for the year in
which
it was introduced explains this in more detail.

I agree, and while that may be a source of distortion, it isnt Doppler
distortion.

"Bob Cain" wrote in message
...


William Sommerwerck wrote:

Can any of you provide an explanation of how an acoustic wave
driving a diaphragm and passing the sound wave through it is
in any way different than the diaphragm being driven by a motor
being supplied with the exact electrical analog of that acoustic
wave?


There is no difference (with one exception, given below).

In the 1980 JAES article explaining the design and development of the
QUAD
ESL-63 speaker system, Peter Walker makes this point explicitly -- the
sound
impinging the diaphragm sets it in motion, and that motion, in turn,
moves the
air on the other side. Mechanical energy IS the energy of motion; it
cannot
magically "pass through" the diaphragm without moving it.

William, do you see that this argues against Doppler
distortion being a phenomenon that occurs because of some
wierd mixing at the piston/air interface which makes the
motion that is imparted there intrinsically distorted? The
ESL is a very good piston.

Put one in a teminated tube, for example, and no Doppler
distortion will be generated.

Under conditions of a linear velocity/pressure relationship
in the air, Doppler distortion is something that happens in
the air gradually. Along any ray, it is developed as a
function of the divergence of the frequency dependant
coupling from equal and flat. In the limit of the actual
piston/air interface it goes to zero.


The one difference is that a voice coil would drive the diaphragm at
only one
point. The ESL-63 is electrostatic, and therefore driven over most of
its
surface.

That's a big difference that is really important but not to
Doppler distortion.


Bob, I think the big guns have gone back to the drawing board for this
one. The "hole in the wall" analogy is elegantly simple, but the math behind
it isn't, especially if one is trying to come up with an equation that shows
that Doppler distortion will result. I'm still not absolutely sure I might
not be missing something, but if I am, I think we can rest assured that
someone will call me on it. I don't mind, this discussion has given me some
much needed mental exercise, and I've enjoyed it!:-)

Porky wrote:

Jim, have you ever seen a speaker with a passive radiator? In fact the
diphragm both is driven by the acoustic wave and allows some sound to pass
through it, but what if the the diaphragm were soundproof" If it were low
enough in mass, you'd still hear sound through it, and if it were massless,
you'd hear all the sound. The question then becomes, does the diapragm
generate Doppler distortion because it is driven by the acoustic wave,
especially at the lower frequencies.

Hey, another good one!


Bob
--

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

A. Einstein

"Bob Cain" wrote in message
...


Porky wrote:

Jim, have you ever seen a speaker with a passive radiator? In fact
the
diphragm both is driven by the acoustic wave and allows some sound to
pass
through it, but what if the the diaphragm were soundproof" If it were
low
enough in mass, you'd still hear sound through it, and if it were
massless,
you'd hear all the sound. The question then becomes, does the diapragm
generate Doppler distortion because it is driven by the acoustic wave,
especially at the lower frequencies.

Hey, another good one!

If you accept Doppler "distortion" as described by others, then instruments
producing multiple tones has the problem. Hit two keys on the piano and the
wood vibrates for both sounds.

What a freaking miss! Thank God my ears are not trained enough to hear it!

On Tue, 24 Aug 2004 19:48:42 -0700, "Jim Carr"
wrote:

"Bob Cain" wrote in message
...


Porky wrote:

Jim, have you ever seen a speaker with a passive radiator? In fact
the
diphragm both is driven by the acoustic wave and allows some sound to
pass
through it, but what if the the diaphragm were soundproof" If it were
low
enough in mass, you'd still hear sound through it, and if it were
massless,
you'd hear all the sound. The question then becomes, does the diapragm
generate Doppler distortion because it is driven by the acoustic wave,
especially at the lower frequencies.

Hey, another good one!

Actually, it would seem that the diaphragm should do the
'reciprocity' thing you were talking about earlier, and not change the
sound.

If you accept Doppler "distortion" as described by others, then instruments
producing multiple tones has the problem. Hit two keys on the piano and the
wood vibrates for both sounds.

Yes, it's true, but the piano (and almost all instruments')
soundboard moves a very small amount (the soundboard's large surface
area makes up for the small movement and gives the instrument decent
volume), and so the doppler effect/distortion generated is
insignificant.


What a freaking miss!

Do you mean mess, or is there some lady involved whom I haven't
heard about?

Thank God my ears are not trained enough to hear it!


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

"Jim Carr" wrote in message
news:t3TWc.21701$L94.6656@fed1read07...
"Bob Cain" wrote in message
...


Porky wrote:

Jim, have you ever seen a speaker with a passive radiator? In fact
the
diphragm both is driven by the acoustic wave and allows some sound to
pass
through it, but what if the the diaphragm were soundproof" If it were
low
enough in mass, you'd still hear sound through it, and if it were
massless,
you'd hear all the sound. The question then becomes, does the diapragm
generate Doppler distortion because it is driven by the acoustic wave,
especially at the lower frequencies.

Hey, another good one!

If you accept Doppler "distortion" as described by others, then
instruments
producing multiple tones has the problem. Hit two keys on the piano and
the
wood vibrates for both sounds.

What a freaking miss! Thank God my ears are not trained enough to hear it!

My position (I think!:-)) is that any thing, be it speaker, instrument,
etc, that produces a complex waveform as a gestalt doesn't introduce Doppler
distortion because the sound wave is created as a single complex entity.
If a speaker produces Doppler shift, then a guitar or piano string, or any
other musical instrument or portion thereof which vibrates and whose
individual notes have high frequency components (i.e. they aren't pure
sinewave tones, which would include almost all musical instruments that have
anything that vibrates as a soundsource) would also produce Doppler shift
with every individual note as well as with combinations of notes played, and
if this were the case then Doppler shift would be a part of the natural
order of things musical, and Doppler shift could thus be entirely
disregarded as a source of "distortion", period!
I think this should pretty much drive the final nail in the Doppler
distortion issue's coffin, because if speakers introduce Doppler shift then
so does everything else which vibrates to produce sound. I still don't think
Doppler shift is introduced by speakers opperating under normal conditions,
but if it is, it's a part of the natural order and not distortion at all!:-)

"Ben Bradley" wrote in message
...

What a freaking miss!

Do you mean mess, or is there some lady involved whom I haven't
heard about?

Oh, I meant miss alright. Christian Doppler's youngest daughter, Wilda. When
Doppler's wife left him and took their daughter, they rode away on a train.
His daughter was screaming the whole time. It was then that he noticed the
pitch seemingly change. Over the years people assumed he meant whistle, not
Wilda.

"Jim Carr" wrote in message
news:HsVWc.23452$L94.20600@fed1read07...
"Ben Bradley" wrote in message
...

What a freaking miss!

Do you mean mess, or is there some lady involved whom I haven't
heard about?

Oh, I meant miss alright. Christian Doppler's youngest daughter, Wilda.
When
Doppler's wife left him and took their daughter, they rode away on a
train.
His daughter was screaming the whole time. It was then that he noticed the
pitch seemingly change. Over the years people assumed he meant whistle,
not
Wilda.

Hmmm, Google didn't have anything on a Wilda Doppler, and a brief search
didn't even turn up anything about a marriage, could it be that Jim is doing
a bit of leg pulling? :-)
However, I did find the following at
http://www-gap.dcs.st-and.ac.uk/~his...s/Doppler.html :
"Although changes in colours were impossible to observe with the
instruments of the time, the situation with sound was rather different. As
early as 1845 experiments were conducted with musicians on railway trains
playing instruments and other trained musicians writing down the apparent
note as the train approached them and receded from them. In 1846 Doppler
published a better version of his principle where he considered both the
motion of the source and the motion of the observer.
Not everyone of course was immedately convinced by Doppler's theory. His
most vigorous opponent was Petzval, by this time professor of mathematics at
the University of Vienna. Their dispute was based on a misunderstanding, in
some sense both were correct but they could not see that they were arguing
about different things."

The second paragraph seems to parallel what has been going on in this
thread. *LOL*

BTW, http://www.kettering.edu/~drussell/Demos.html has links to some neat
animated gifs that illustrate various acoustic and other phenomena.

http://www.kettering.edu/~drussell/L...html#acoustics is a list of
acoustics related links.

I didn't check to see if any of them directly applied to this thread, but
they do seem like some of them might be useful for recordists and music
lovers.

Jim Carr wrote:

If you accept Doppler "distortion" as described by others, then instruments
producing multiple tones has the problem. Hit two keys on the piano and the
wood vibrates for both sounds.

Yes, absolutely! There are all _kinds_ of weird modulation effects going on
between notes on pianos. That is why pianos are so difficult to simulate
believably.

On the whole, though, the sympathetic vibration effects in a piano are
going to swamp everything else... and some of them are not even harmonic!
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Bob,

The hole in the wall is a good question.

But I think a hole in the hall and a speaker are not identical. If
you have two speakers, one producing a 50 Hz wave and a second,
producing a 4 kHz wave, and both waves pass through the hole, there is
no internaction and no Doppling.

If I place a membrane over the hole, the membrane will revieve the two
waves and vibrate as the sum of them and reradiate the two waves and
again there will be no Doppler. There is no relative motion between
the Rx and Tx. There is no relative motion between the original Tx
and the Rx. The membrane in the middle just follws the air thats
already moving.
If you want to think of the membrane as a Rx a nd a Tx, then there is
Doppler created when the membrane receives the wave and then exactly
the opposite Doppler is created when the membrane re-transmits the
wave.

By the way, Doppler has nothing to do with the speed relative to the
meduim as others are talking about, it has everything to do with the
relative speed of the Tx and the Rx.

THE KEY IS RELATIVE MOTION BETWEEN THE TX AND RX. NOTHING ELSE.

Mark