Hello,

A car is designed to carry a loudspeaker. The object is to measure the
speaker characteristics to see if it is desirable so that people can
hear the audio clearly while the car is moving at least 45 km per hour.
What would be the best way to measure or characterize the sound coming
out of it?

I was thinking that the Doppler shift effect can affect the actual
sound that is coming out of the speaker, so any frequency analysis
measurement may not represent the actual frequency coming out of the
speaker. But a sound pressure measurement might help in determining how
long the audio can remain audible. Thanks!

On 17 Apr 2006 11:35:26 -0700, wrote:

Hello,

A car is designed to carry a loudspeaker. The object is to measure the
speaker characteristics to see if it is desirable so that people can
hear the audio clearly while the car is moving at least 45 km per hour.
What would be the best way to measure or characterize the sound coming
out of it?

I was thinking that the Doppler shift effect can affect the actual
sound that is coming out of the speaker, so any frequency analysis
measurement may not represent the actual frequency coming out of the
speaker. But a sound pressure measurement might help in determining how
long the audio can remain audible. Thanks!

If the people are in the car with the speaker, you don't need to worry
about Doppler - even in an open-topped car.

If the idea is to make a noise that pedestrians can hear - shame on
you!

d

--
Pearce Consulting
http://www.pearce.uk.com

Actually, it's the second thing that you mentioned that I wanted to
know. It's not geared to for pedestrians, but in a controlled
environment away from the streets.

On 17 Apr 2006 12:48:26 -0700, wrote:

Actually, it's the second thing that you mentioned that I wanted to
know. It's not geared to for pedestrians, but in a controlled
environment away from the streets.

That's fine then. Don't worry about Doppler for car speeds. Unless you
are thinking about approaching supersonic, that is.

d

--
Pearce Consulting
http://www.pearce.uk.com

That's fine then. Don't worry about Doppler for car speeds. Unless you
are thinking about approaching supersonic, that is.

Nonsense!

Just a few miles an hour, under the right circumstances can cause
considerable frequency shift. How do you think a Leslie speaker works?

James. )



"Don Pearce" wrote in message
...
On 17 Apr 2006 12:48:26 -0700, wrote:

Actually, it's the second thing that you mentioned that I wanted to
know. It's not geared to for pedestrians, but in a controlled
environment away from the streets.


d

--
Pearce Consulting
http://www.pearce.uk.com

James Lehman wrote:
That's fine then. Don't worry about Doppler for car speeds. Unless you
are thinking about approaching supersonic, that is.

Nonsense!

Just a few miles an hour, under the right circumstances can cause
considerable frequency shift. How do you think a Leslie speaker works?

James. )


Nonetheless, it's a non-issue. There's no cure for it. (beyond stopping
the car) ...just a fact of life and an immutable property of physics.

jak


"Don Pearce" wrote in message
...
On 17 Apr 2006 12:48:26 -0700, wrote:

Actually, it's the second thing that you mentioned that I wanted to
know. It's not geared to for pedestrians, but in a controlled
environment away from the streets.

d

--
Pearce Consulting
http://www.pearce.uk.com

In a controlled experiment, speakers in a moving car can actually add a very
interesting effect to music; especially when there are a few large solid
buildings to bounce sound around. That way the listener gets many audio
paths that are all slightly shifted at different angles from the moving
source. The natural effect is bound to be a lot more complex and appealing
than any rack mount digital doohickey could conjure up.

James. )



"jakdedert" wrote in message
...
James Lehman wrote:
That's fine then. Don't worry about Doppler for car speeds. Unless you
are thinking about approaching supersonic, that is.

Nonsense!

Just a few miles an hour, under the right circumstances can cause
considerable frequency shift. How do you think a Leslie speaker works?

James. )


Nonetheless, it's a non-issue. There's no cure for it. (beyond stopping
the car) ...just a fact of life and an immutable property of physics.

jak


"Don Pearce" wrote in message
...
On 17 Apr 2006 12:48:26 -0700, wrote:

Actually, it's the second thing that you mentioned that I wanted to
know. It's not geared to for pedestrians, but in a controlled
environment away from the streets.

d

--
Pearce Consulting
http://www.pearce.uk.com

James Lehman wrote:
In a controlled experiment, speakers in a moving car can actually add a very
interesting effect to music; especially when there are a few large solid
buildings to bounce sound around. That way the listener gets many audio
paths that are all slightly shifted at different angles from the moving
source. The natural effect is bound to be a lot more complex and appealing
than any rack mount digital doohickey could conjure up.

James. )



"jakdedert" wrote in message
...
James Lehman wrote:
That's fine then. Don't worry about Doppler for car speeds. Unless you
are thinking about approaching supersonic, that is.
Nonsense!

Just a few miles an hour, under the right circumstances can cause
considerable frequency shift. How do you think a Leslie speaker works?

James. )


Nonetheless, it's a non-issue. There's no cure for it. (beyond stopping
the car) ...just a fact of life and an immutable property of physics.

jak

"Don Pearce" wrote in message
...
On 17 Apr 2006 12:48:26 -0700, wrote:

Actually, it's the second thing that you mentioned that I wanted to
know. It's not geared to for pedestrians, but in a controlled
environment away from the streets.
d

--
Pearce Consulting
http://www.pearce.uk.com





One could, theoretically, compensate for Doppler shifting a moving sound
source by a controlled frequency (and speed) shifting; but the
correction would only be valid at one particular listening position. I
don't see the point, beyond experimentation.

jak

Just a few miles an hour, under the right circumstances can cause
considerable frequency shift. How do you think a Leslie speaker works?

45 mph is a shift of 1.22 times the frequency, assuming that you are ON the
road and the car is driving straight towards you. That is quite a shift,
yes.

Now, keep in mind that the speaker itself will keep it's frequency response.
A muffled speaker will not sound "brighter" if you drive with 80 mph towards
a listener. It will only shift the pitch, not the "timbre", like playing a
33 rpm record on 45 rpm speed.

If your main concern is speech and long range audibility, you might want to
consider those 100v horns.

Gert

On Mon, 17 Apr 2006 16:54:46 -0500, jakdedert wrote:


James Lehman wrote:
That's fine then. Don't worry about Doppler for car speeds. Unless you
are thinking about approaching supersonic, that is.

Nonsense!

Just a few miles an hour, under the right circumstances can cause
considerable frequency shift. How do you think a Leslie speaker works?

James. )


Nonetheless, it's a non-issue. There's no cure for it. (beyond stopping
the car) ...just a fact of life and an immutable property of physics.

Sure there is. Sit on a seat connected to the same frame as the speaker
and there will be no doppler effect. It's when you've fallen out of the
car that it'll exist and you'll have too many other problems like that tree
you're about to hit to care.

On Mon, 17 Apr 2006 20:00:27 GMT, (Don Pearce)
wrote:

That's fine then. Don't worry about Doppler for car speeds. Unless you
are thinking about approaching supersonic, that is.

The classic example of Doppler is the emergency vehicle siren
approaching and retreating. At well below supersonic speeds.

On Mon, 17 Apr 2006 21:51:27 GMT, "James Lehman"
wrote:

That's fine then. Don't worry about Doppler for car speeds. Unless you
are thinking about approaching supersonic, that is.

Nonsense!

Just a few miles an hour, under the right circumstances can cause
considerable frequency shift. How do you think a Leslie speaker works?

If the listener is rotating with the Leslie speaker, it doesn't work!

Doppler shift is a relativistic effect, so it does not effect
listeners in the same space/time frame as the speaker, i.e. passengers
in the car. Listeners waiting to cross the road will of course hear
the usual doppler shift as the car goes by. This does of course apply
at all speeds, even supersonic - otherwise you wouldn't have been able
to order more champagne on Concorde.

--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Tue, 18 Apr 2006 00:11:37 +0100, Laurence Payne
lpayneNOSPAM@dslDOTpipexDOTcom wrote:

On Mon, 17 Apr 2006 20:00:27 GMT, (Don Pearce)
wrote:

That's fine then. Don't worry about Doppler for car speeds. Unless you
are thinking about approaching supersonic, that is.

The classic example of Doppler is the emergency vehicle siren
approaching and retreating. At well below supersonic speeds.

But you don't hear that effect if you are *in* the vehicle. And
cockpit alarms work just fine in a Space Shuttle doing Mach 5.

--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Mon, 17 Apr 2006 21:51:27 GMT, "James Lehman"
wrote:

That's fine then. Don't worry about Doppler for car speeds. Unless you
are thinking about approaching supersonic, that is.

Nonsense!

Just a few miles an hour, under the right circumstances can cause
considerable frequency shift. How do you think a Leslie speaker works?

James. )


They work by having the speaker moving and the listener stationary.
When you are in a car, moving along at the same speed as the speaker,
there is *no* net Doppler.

d

--
Pearce Consulting
http://www.pearce.uk.com

Wasn't the original poster talking about a car with a speaker on it,
observed (or rather heard) from outside the car, on the road?

It wasn't perfectly clear to me what kind of setup was being described.

On Tue, 18 Apr 2006 06:08:06 -0400, "mc"
wrote:

Wasn't the original poster talking about a car with a speaker on it,
observed (or rather heard) from outside the car, on the road?

It wasn't perfectly clear to me what kind of setup was being described.


No, I don't think so. He appeared to be talking about listening within
the car, but the car was open, so it would be listening within a
moving air stream. The result of this would be (assuming speakers at
the back, and listening further forwards) that although there would be
no net Doppler change - the listening end would cancel the speaker end
- as the car travelled faster, the sound would have to travel further
to reach the ear, so it would be attenuated. If the car approached the
speed of sound, the distance of travel would approach infinite, and
the volume of the sound would fade away to nothing.

d

--
Pearce Consulting
http://www.pearce.uk.com

In .com, on 04/17/06

at 11:35 AM, said:

Hello,

A car is designed to carry a loudspeaker. The object is to measure the
speaker characteristics to see if it is desirable so that people can
hear the audio clearly while the car is moving at least 45 km per
hour. What would be the best way to measure or characterize the sound
coming out of it?

I was thinking that the Doppler shift effect can affect the actual
sound that is coming out of the speaker, so any frequency analysis
measurement may not represent the actual frequency coming out of the
speaker. But a sound pressure measurement might help in determining
how long the audio can remain audible. Thanks!

Doppler shift involves RELATIVE movement. If you and the car are
traveling together, there is no shift for you, but an observer in a
passing car or a pedestrian will experience doppler shift.

One could introduce a nag with moving air, but compared to the speed of
sound, a little wind does not represent much frequency modulation. I
would expect that wind and car noises would introduce many more
measurement difficulties than a potential frequency shift due to moving
air. Simple mechanical noise and impulses (resulting from bumps in the
road, engine noises, etc.) that excite a resonance in the measurement
microphone or the speaker under test will cause much more trouble.

-----------------------------------------------------------
spam:
wordgame:123(abc):14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15
13 (Barry Mann)
[sorry about the puzzle, spammers are ruining my mailbox]
-----------------------------------------------------------

AZ Nomad wrote:
On Mon, 17 Apr 2006 16:54:46 -0500, jakdedert wrote:


James Lehman wrote:
That's fine then. Don't worry about Doppler for car speeds. Unless you
are thinking about approaching supersonic, that is.
Nonsense!

Just a few miles an hour, under the right circumstances can cause
considerable frequency shift. How do you think a Leslie speaker works?

James. )


Nonetheless, it's a non-issue. There's no cure for it. (beyond stopping
the car) ...just a fact of life and an immutable property of physics.

Sure there is. Sit on a seat connected to the same frame as the speaker
and there will be no doppler effect. It's when you've fallen out of the
car that it'll exist and you'll have too many other problems like that tree
you're about to hit to care.


Not if the car's sitting still...no doppler shift and no problem with
the the tree....

g

jak

On Tue, 18 Apr 2006 10:17:27 -0500, jakdedert wrote:


AZ Nomad wrote:
On Mon, 17 Apr 2006 16:54:46 -0500, jakdedert wrote:


James Lehman wrote:
That's fine then. Don't worry about Doppler for car speeds. Unless you
are thinking about approaching supersonic, that is.
Nonsense!

Just a few miles an hour, under the right circumstances can cause
considerable frequency shift. How do you think a Leslie speaker works?

James. )


Nonetheless, it's a non-issue. There's no cure for it. (beyond stopping
the car) ...just a fact of life and an immutable property of physics.

Sure there is. Sit on a seat connected to the same frame as the speaker
and there will be no doppler effect. It's when you've fallen out of the
car that it'll exist and you'll have too many other problems like that tree
you're about to hit to care.


Not if the car's sitting still...no doppler shift and no problem with
the the tree....

g

Shouldn't be a problem staying in the car. If you go flying out
of a parked car....

In article , AZ Nomad wrote:
On Tue, 18 Apr 2006 10:17:27 -0500, jakdedert wrote:


AZ Nomad wrote:
On Mon, 17 Apr 2006 16:54:46 -0500, jakdedert
wrote:


James Lehman wrote:
That's fine then. Don't worry about Doppler for car speeds. Unless you
are thinking about approaching supersonic, that is.
Nonsense!

Just a few miles an hour, under the right circumstances can cause
considerable frequency shift. How do you think a Leslie speaker works?

James. )


Nonetheless, it's a non-issue. There's no cure for it. (beyond stopping
the car) ...just a fact of life and an immutable property of physics.

Sure there is. Sit on a seat connected to the same frame as the speaker
and there will be no doppler effect. It's when you've fallen out of the
car that it'll exist and you'll have too many other problems like that tree
you're about to hit to care.


Not if the car's sitting still...no doppler shift and no problem with
the the tree....

g

Shouldn't be a problem staying in the car. If you go flying out
of a parked car....

I am trying to figure out how fast you have to swing your head around to hear
doppler. All I get is a headache and sore neck.

greg

Get a small, light weight set of computer speakers and hold them in your
hands. Wave them around in the air around your head like a windmill.


James. )


"GregS" wrote in message
...
In article , AZ
Nomad wrote:
On Tue, 18 Apr 2006 10:17:27 -0500, jakdedert
wrote:


AZ Nomad wrote:
On Mon, 17 Apr 2006 16:54:46 -0500, jakdedert

wrote:


James Lehman wrote:
That's fine then. Don't worry about Doppler for car speeds. Unless
you
are thinking about approaching supersonic, that is.
Nonsense!

Just a few miles an hour, under the right circumstances can cause
considerable frequency shift. How do you think a Leslie speaker
works?

James. )


Nonetheless, it's a non-issue. There's no cure for it. (beyond
stopping
the car) ...just a fact of life and an immutable property of physics.

Sure there is. Sit on a seat connected to the same frame as the
speaker
and there will be no doppler effect. It's when you've fallen out of
the
car that it'll exist and you'll have too many other problems like that
tree
you're about to hit to care.


Not if the car's sitting still...no doppler shift and no problem with
the the tree....

g

Shouldn't be a problem staying in the car. If you go flying out
of a parked car....

I am trying to figure out how fast you have to swing your head around to
hear
doppler. All I get is a headache and sore neck.

greg

The effect of a Leslie speaker comes from the mixture and interference of
the back of the speaker cone, which is fixed and the moving hole in the drum
in front of the speaker cone. You are correct in that Doppler effect is
relative to the listener, but a listener can not be both fixed and moving at
the same time.

James. )


"Stewart Pinkerton" wrote in message
...
On Mon, 17 Apr 2006 21:51:27 GMT, "James Lehman"
wrote:

That's fine then. Don't worry about Doppler for car speeds. Unless you
are thinking about approaching supersonic, that is.

Nonsense!

Just a few miles an hour, under the right circumstances can cause
considerable frequency shift. How do you think a Leslie speaker works?

If the listener is rotating with the Leslie speaker, it doesn't work!

Doppler shift is a relativistic effect, so it does not effect
listeners in the same space/time frame as the speaker, i.e. passengers
in the car. Listeners waiting to cross the road will of course hear
the usual doppler shift as the car goes by. This does of course apply
at all speeds, even supersonic - otherwise you wouldn't have been able
to order more champagne on Concorde.

--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Wed, 19 Apr 2006 03:32:25 GMT, "James Lehman"
wrote:

Get a small, light weight set of computer speakers and hold them in your
hands. Wave them around in the air around your head like a windmill.

You are then moving the speakers relative to your ears - different
situation from being a passenger in the same car as the speakers.

--

Stewart Pinkerton | Music is Art - Audio is Engineering

Posted Via Usenet.com Premium Usenet Newsgroup Services
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On Wed, 19 Apr 2006 03:32:25 GMT, "James Lehman"
wrote:

The effect of a Leslie speaker comes from the mixture and interference of
the back of the speaker cone, which is fixed and the moving hole in the drum
in front of the speaker cone. You are correct in that Doppler effect is
relative to the listener, but a listener can not be both fixed and moving at
the same time.

Of course he can - I am moving at a bit less than 1,000mph right now,
since I'm on the surface of a rotating planet - doesn't seem to affect
my hi-fi, though!

--

Stewart Pinkerton | Music is Art - Audio is Engineering

Posted Via Usenet.com Premium Usenet Newsgroup Services
----------------------------------------------------------
** SPEED ** RETENTION ** COMPLETION ** ANONYMITY **
----------------------------------------------------------
http://www.usenet.com

On Wed, 19 Apr 2006 06:53:12 +0100, Stewart Pinkerton wrote:


On Wed, 19 Apr 2006 03:32:25 GMT, "James Lehman"
wrote:

The effect of a Leslie speaker comes from the mixture and interference of
the back of the speaker cone, which is fixed and the moving hole in the drum
in front of the speaker cone. You are correct in that Doppler effect is
relative to the listener, but a listener can not be both fixed and moving at
the same time.

Of course he can - I am moving at a bit less than 1,000mph right now,
since I'm on the surface of a rotating planet - doesn't seem to affect
my hi-fi, though!

That's because you're on the same planet.

What if the stereo was loud enough to be heard from another planet? (and
how the hell could the sound travel through vacuum? Better call the Star Trek
script writers) You'd need to correct for doppler effect.

On Wed, 19 Apr 2006 14:14:38 GMT, AZ Nomad
wrote:

On Wed, 19 Apr 2006 06:53:12 +0100, Stewart Pinkerton wrote:


On Wed, 19 Apr 2006 03:32:25 GMT, "James Lehman"
wrote:

The effect of a Leslie speaker comes from the mixture and interference of
the back of the speaker cone, which is fixed and the moving hole in the drum
in front of the speaker cone. You are correct in that Doppler effect is
relative to the listener, but a listener can not be both fixed and moving at
the same time.

Of course he can - I am moving at a bit less than 1,000mph right now,
since I'm on the surface of a rotating planet - doesn't seem to affect
my hi-fi, though!

That's because you're on the same planet.

What if the stereo was loud enough to be heard from another planet? (and
how the hell could the sound travel through vacuum? Better call the Star Trek
script writers) You'd need to correct for doppler effect.

Irrelevant, since the question concerns speaker and listeners in the
same car, hence with no *relative* movement, and no Doppler effect.

--

Stewart Pinkerton | Music is Art - Audio is Engineering

On Wed, 19 Apr 2006 17:52:27 +0100, Stewart Pinkerton wrote:


On Wed, 19 Apr 2006 14:14:38 GMT, AZ Nomad
wrote:

On Wed, 19 Apr 2006 06:53:12 +0100, Stewart Pinkerton wrote:


On Wed, 19 Apr 2006 03:32:25 GMT, "James Lehman"
wrote:

The effect of a Leslie speaker comes from the mixture and interference of
the back of the speaker cone, which is fixed and the moving hole in the drum
in front of the speaker cone. You are correct in that Doppler effect is
relative to the listener, but a listener can not be both fixed and moving at
the same time.

Of course he can - I am moving at a bit less than 1,000mph right now,
since I'm on the surface of a rotating planet - doesn't seem to affect
my hi-fi, though!

That's because you're on the same planet.

What if the stereo was loud enough to be heard from another planet? (and
how the hell could the sound travel through vacuum? Better call the Star Trek
script writers) You'd need to correct for doppler effect.

Irrelevant, since the question concerns speaker and listeners in the
same car, hence with no *relative* movement, and no Doppler effect.

I didn't read that in the original post. It simply asked how the sound
would be from a car going 45mph. Probably on the same planet.

On Thu, 20 Apr 2006 05:50:43 GMT, AZ Nomad
wrote:

On Wed, 19 Apr 2006 17:52:27 +0100, Stewart Pinkerton wrote:


On Wed, 19 Apr 2006 14:14:38 GMT, AZ Nomad
wrote:

On Wed, 19 Apr 2006 06:53:12 +0100, Stewart Pinkerton wrote:


On Wed, 19 Apr 2006 03:32:25 GMT, "James Lehman"
wrote:

The effect of a Leslie speaker comes from the mixture and interference of
the back of the speaker cone, which is fixed and the moving hole in the drum
in front of the speaker cone. You are correct in that Doppler effect is
relative to the listener, but a listener can not be both fixed and moving at
the same time.

Of course he can - I am moving at a bit less than 1,000mph right now,
since I'm on the surface of a rotating planet - doesn't seem to affect
my hi-fi, though!

That's because you're on the same planet.

What if the stereo was loud enough to be heard from another planet? (and
how the hell could the sound travel through vacuum? Better call the Star Trek
script writers) You'd need to correct for doppler effect.

Irrelevant, since the question concerns speaker and listeners in the
same car, hence with no *relative* movement, and no Doppler effect.

I didn't read that in the original post. It simply asked how the sound
would be from a car going 45mph. Probably on the same planet.

Not *from* a car, *in* a car.

--

Stewart Pinkerton | Music is Art - Audio is Engineering