Hello!
I've been looking in modern physics textbooks for a reference to
the acoustic transverse Doppler effect.

In other words, the Doppler shift that you'd expect to hear if the
source was stationary wrt the air, and you were moving past at v m/s,
and pointed your rifle mic out at 90 degrees to your direction of
motion ... when you hear a quick burst of signal entering your
directional mic, what sort of frequency shift should it have?

Anyone know of a good reference source that gives the "official"
equation for this shift?



PS: I know what =I= think it ought to be, but I can't find the damned
thing in print.
PPS: If modern physics people don't know about the effect, can I lay a
claim to it? grin


=Erk= (Eric Baird)

Eric Baird wrote:
Hello!
I've been looking in modern physics textbooks for a reference to
the acoustic transverse Doppler effect.

In other words, the Doppler shift that you'd expect to hear if the
source was stationary wrt the air, and you were moving past at v m/s,
and pointed your rifle mic out at 90 degrees to your direction of
motion ... when you hear a quick burst of signal entering your
directional mic, what sort of frequency shift should it have?

Anyone know of a good reference source that gives the "official"
equation for this shift?



Acoustic Doppler shifts depend only on the compenent of motion
toward or away from the listener, so there is no transverse
Doppler shift.


PS: I know what =I= think it ought to be, but I can't find the damned
thing in print.
PPS: If modern physics people don't know about the effect, can I lay a
claim to it? grin


Since it doesn't exist, you are welcome to it.

-E


=Erk= (Eric Baird)

EjP wrote:


Eric Baird wrote:

Hello!
I've been looking in modern physics textbooks for a reference to
the acoustic transverse Doppler effect.
In other words, the Doppler shift that you'd expect to hear if the
source was stationary wrt the air, and you were moving past at v m/s,
and pointed your rifle mic out at 90 degrees to your direction of
motion ... when you hear a quick burst of signal entering your
directional mic, what sort of frequency shift should it have?

Anyone know of a good reference source that gives the "official"
equation for this shift?


Acoustic Doppler shifts depend only on the compenent of motion
toward or away from the listener, so there is no transverse
Doppler shift.


....unless of course the source were moving fast enough to
consider relativistic effects of course, in which case
it would be exactly the same as the EM transverse Doppler
shift.


PS: I know what =I= think it ought to be, but I can't find the damned
thing in print. PPS: If modern physics people don't know about the
effect, can I lay a
claim to it? grin


Since it doesn't exist, you are welcome to it.

-E


=Erk= (Eric Baird)

Eric Baird wrote:

In other words, the Doppler shift that you'd expect to hear if the
source was stationary wrt the air, and you were moving past at v m/s,
and pointed your rifle mic out at 90 degrees to your direction of
motion ... when you hear a quick burst of signal entering your
directional mic, what sort of frequency shift should it have?


The rifle mic character implies a very directional microphone, so that
hypothetically, source sound is only received when adjacent to the sound
source. FYI, the beamwidth of such mics is not so narrow.

The sound entering the microphone when adjacent to the source will be
the same frequency as emitted since at that position, for an instant,
the distance to the source is not changing.

However the rate of change of frequency with time will be a maximum, as
it is swinging from a higher frequency as you were approaching, to a
lower frequency as you soon will be moving further away.


Anyone know of a good reference source that gives the "official"
equation for this shift?


See the FAQ file in my web page. This gives accurate values when you are
approaching, and when you are receding from, a sound source. For the
braodside pass by, the frequency swings from a high frequency to a low
frequency. The frequency behavior with time can be calculated according
to plane geometry (a simple calculation when your path is a straight
line). The velocity used in every case is the rate of change of distance
to the source.

--------- www.CampanellaAcoustics.com ---------

"I have simply studied carefully whatever I've undertaken, and tried to
hold a reserve that would carry me through." - Charles A. Lindbergh.

"As for background noise level; 35 dBA is a good classroom; 45 dBA is a
sound masking system!" - Anthony K. Hoover

On Fri, 13 Feb 2004 02:15:11 +0000 (UTC), Eric Baird
wrote:

Hello!
I've been looking in modern physics textbooks for a reference to
the acoustic transverse Doppler effect.

In other words, the Doppler shift that you'd expect to hear if the
source was stationary wrt the air, and you were moving past at v m/s,
and pointed your rifle mic out at 90 degrees to your direction of
motion ... when you hear a quick burst of signal entering your
directional mic, what sort of frequency shift should it have?

Anyone know of a good reference source that gives the "official"
equation for this shift?



PS: I know what =I= think it ought to be, but I can't find the damned
thing in print.
PPS: If modern physics people don't know about the effect, can I lay a
claim to it? grin


=Erk= (Eric Baird)

Assume a set of axes, the vertical of which is represented by the
direction from the source to the microphone and draw on them a vector
representing the speed and direction of travel of the source. The
length of the Y (cosine) portion of this vector represents the net
speed of the source towards (or away from) the microphone at that
instant. Add (or subtract when moving away) this to the speed of sound
to get the ratio of perceived to actual frequency.

Once you have this clear in your head, just derive the actual equation
relating angle, velocity and frequency.

d

_____________________________

http://www.pearce.uk.com

Eric Baird wrote:

Hello!
I've been looking in modern physics textbooks for a reference to
the acoustic transverse Doppler effect.

In other words, the Doppler shift that you'd expect to hear if the
source was stationary wrt the air, and you were moving past at v m/s,
and pointed your rifle mic out at 90 degrees to your direction of
motion ... when you hear a quick burst of signal entering your
directional mic, what sort of frequency shift should it have?

Anyone know of a good reference source that gives the "official"
equation for this shift?

You want to be *very* careful about whether this is a relativistic
example (light) or a Galilean one (sound). It makes a difference.

For velocities at an arbitrary angle theta with ful reativisitic
correciton, Jackson gives

u_parallel = (u'_parallel + v)/(1+(v dot u')/c^2)
u_perp = u'_perp/(gamma_v(1+(v dot u')/c^2))

http://www.physics.umanitoba.ca/~souther/waves02/feb0402/sld011.htm

Google
"transverse doppler effect" 423 hits
"transverse doppler shift" 212 hits

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!

A reference to Jackson brings back memories (painful ones) of graduate
E&M. Thank for the memory (i think)...RonMan

In article , Uncle Al
wrote:

Eric Baird wrote:

You want to be *very* careful about whether this is a relativistic
example (light) or a Galilean one (sound). It makes a difference.

For velocities at an arbitrary angle theta with ful reativisitic
correciton, Jackson gives

u_parallel = (u'_parallel + v)/(1+(v dot u')/c^2)
u_perp = u'_perp/(gamma_v(1+(v dot u')/c^2))

http://www.physics.umanitoba.ca/~souther/waves02/feb0402/sld011.htm

Google
"transverse doppler effect" 423 hits
"transverse doppler shift" 212 hits

On Fri, 13 Feb 2004 09:21:13 +0000, Don Pearce
wrote:

Once you have this clear in your head, just derive the actual equation
relating angle, velocity and frequency.

As I said I've already derived it ... I'd just like to be able to find
an example of the effect in print in a modern reference book.

On Fri, 13 Feb 2004 09:41:23 -0800, Uncle Al wrote:

Eric Baird wrote:

Hello!
I've been looking in modern physics textbooks for a reference to
the acoustic transverse Doppler effect.

In other words, the Doppler shift that you'd expect to hear if the
source was stationary wrt the air, and you were moving past at v m/s,
and pointed your rifle mic out at 90 degrees to your direction of
motion ... when you hear a quick burst of signal entering your
directional mic, what sort of frequency shift should it have?

Anyone know of a good reference source that gives the "official"
equation for this shift?

You want to be *very* careful about whether this is a relativistic
example (light) or a Galilean one (sound). It makes a difference.

Indeed.
This is for an acoustic calculation, for sound in air, when the
transmission medium is stationary wrt the source, but when the
detector is moving relative to source and medium at v m/s.

As I stated above.


For velocities at an arbitrary angle theta with ful reativisitic
correciton, Jackson gives

SNIP!!!

That's an answer to a different question.
I was asking about a simple acoustic effect, sound in air, no use of
special relativity involved.


Google
"transverse doppler effect" 423 hits
"transverse doppler shift" 212 hits

Yes, but do any of those hits give the ACOUSTIC transverse Doppler
prediction?

Please read more carefully.

=Erk= (Eric Baird)

"Eric Baird" wrote in message
...
Hello!
I've been looking in modern physics textbooks for a reference to
the acoustic transverse Doppler effect.

What acoustic transverse effect?
The frequency shift depende only on the component of relative velocity along
a line between the detector and the source.

Franz