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RichD RichD is offline
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Default audio telescope?

This may be a dumb question, I never studied acoustics....

If you look into the wrong end of a telescope,
everything looks reduced, 'anti-magnified'.
Is there anything analogous acoustically?

In both cases, the phenomena is described
by wave equations -

--
Rich
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Louis Boyd Louis Boyd is offline
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Default audio telescope?

RichD wrote:
This may be a dumb question, I never studied acoustics....

If you look into the wrong end of a telescope,
everything looks reduced, 'anti-magnified'.
Is there anything analogous acoustically?

In both cases, the phenomena is described
by wave equations -

--
Rich



It should be simple to demonstrate a Galilean telescope (one positive
and one negative lens) which will magnify or minify an acoustic image
using an ultrasonic imaging device and some common optical lenses.
They would only need to be made of a material with a different velocity
of propagation of sound than a liquid they are submerged in. The
velocity of propagation of sound is somewhat analogous to the velocity
of propagation of electromagnetic energy to demonstrate refraction at
material boundaries.

"Magnify" doesn't have the same meaning in imaging and non-imaging
situations.

An acoustic "telescope" doesn't have to be refractive. A two mirror
Cassegrain reflecting telescope can focus sound as well as
electromagnetic energy. I've experienced that working on microwave
antennas.
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isw isw is offline
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In article
,
RichD wrote:

This may be a dumb question, I never studied acoustics....

If you look into the wrong end of a telescope,
everything looks reduced, 'anti-magnified'.
Is there anything analogous acoustically?

In both cases, the phenomena is described
by wave equations -


There are various sorts of acoustic lenses, and horn-based loudspeakers
are not uncommon. Many speaker systems make use of interference effects,
too -- some, to their detriment, because the "designers" didn't
understand what they were doing ...

Isaac
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"RichD" wrote in message
...
| This may be a dumb question, I never studied acoustics....
|
| If you look into the wrong end of a telescope,
| everything looks reduced, 'anti-magnified'.
| Is there anything analogous acoustically?
|
Look up "megaphone".


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On 21/04/2011 03:48, RichD wrote:
This may be a dumb question, I never studied acoustics....

If you look into the wrong end of a telescope,
everything looks reduced, 'anti-magnified'.
Is there anything analogous acoustically?

In both cases, the phenomena is described
by wave equations -

--
Rich



An old fashioned ear trumpet turned around the wrong way would do
something similar.

An electronic amplifier makes things sound louder, Sound insulation
makes things sound quieter.

The display on a ship sonar allows the image to be zoomed in and out.




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Default audio telescope?


"RichD" wrote in message
...
This may be a dumb question, I never studied acoustics....

If you look into the wrong end of a telescope,
everything looks reduced, 'anti-magnified'.
Is there anything analogous acoustically?

In both cases, the phenomena is described
by wave equations -

--
Rich


This thread is bugging me enormously.

Because its certainly not a dumb question, and despite having an interest in
these subjects it has never occurred to me. And I don't know the answer.

I'm not sure the question has any meaning beyond imaging, and sound waves
aren't typically used for imaging.

You could in principle build sound lenses, but in practice mirrors or phased
arrays (as in sonar) would be more practical. You could artificially
simulate any optical effect in this manner, but as far as I know there is no
practical use for looking down the wrong end of a telescope even when using
light, let alone sound.

I know lots of places where light refraction and reflection is used in
nature, from eyes to fish scales, and lots of places where sound reflection
is used (every large animal's ear, bats etc), but none where sound
refraction is used.


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Hello.

If anyone wants to investigate acoustic mirrors then have a look at :

http://www.andrewgrantham.co.uk/soundmirrors/

http://en.wikipedia.org/wiki/Acoustic_mirror




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On Apr 21, 12:23*am, Louis Boyd wrote:
RichD wrote:
This may be a dumb question, I never studied acoustics....


If you look into the wrong end of a telescope,
everything looks reduced, 'anti-magnified'.
Is there anything analogous acoustically?


In both cases, the phenomena is described
by wave equations -


--
Rich


It should be simple *to demonstrate a Galilean telescope (one positive
and *one negative lens) *which will magnify or minify an acoustic image
* using an ultrasonic imaging *device and some *common optical lenses.
They would only *need to be made of a material with a different velocity
of propagation of sound *than a liquid they are submerged in. *The
velocity of propagation of sound is somewhat *analogous to the velocity
of propagation of electromagnetic energy to demonstrate refraction at
material boundaries.

"Magnify" doesn't have the same meaning in imaging and *non-imaging
situations.

An acoustic "telescope" doesn't have to be refractive. *A two mirror
Cassegrain reflecting telescope *can *focus sound as well as
electromagnetic energy. * I've experienced that working on microwave
antennas.


I remember a demo using a balloon filled with CO2 to focus sound,
though spheres as lenses aren't exactly great for building a
telescope.... Pretty neat way to show a sound analog to optics and
get the ideas of propagation velocity across to intro physics
students.

Not sure I'd like to use a balloon as a hearing aid though...

Frank.
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Hello.

If anyone wants to investigate acoustic mirrors then have a look at :

http://www.andrewgrantham.co.uk/soundmirrors/



Nice!!

I was once shown, some years ago, an "acoustic laser" (maybe at the
University of Maryland Baltimore County campus??): Two large
(half-meter diameter) curved metal mirrors (like shallow woks, or the
curved metal dishes kids slide down snowbanks on), spaced maybe two
meters apart on an optical table to form an acoustic resonator. In the
middle a chunk of "acoustic laser material" consisting of a little
match-box sized box with an omnidirectional microphone at each end, with
each of these connected through a tiny transistor audio amp to a small
speaker on the opposite end.

Took up a lot of table space -- but "lased" nicely.
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Peter Webb wrote:

You could in principle build sound lenses, but in practice mirrors or phased
arrays (as in sonar) would be more practical.


Using parabolic sound mirrors with a microphone at the focal point is
very common for many uses. I see them for sporting events, to focus in
on remote conversations, to capture the sounds of distant animals.

You could artificially
simulate any optical effect in this manner, but as far as I know there is no
practical use for looking down the wrong end of a telescope even when using
light, let alone sound.


Both microscopes and telescopes magnify. Looking at the wrong end of a
telescope makes the image smaller but also makes it dimmer.

So the effect would be to make sounds quieter. Since it is easy to
reduce sound in general with insulation and echo suppression there is
much less call for sound from a very specific direction to be reduced.

Consider listening to a rifle shot - Once I know the direction it came
from what's the point of reducing the volume from only that direction
when I can deaden sound volume it general?

It's not like the speakers at an excessively loud rock concert are close
enough together for a directional deadener to be a better option than
peak blocking ear plugs.

I know lots of places where light refraction and reflection is used in
nature, from eyes to fish scales, and lots of places where sound reflection
is used (every large animal's ear, bats etc), but none where sound
refraction is used.


Ears are wave guides. It starts to push the border between reflection
and refraction just a bit. It demonstrates that there can be a
continium between the two effects.

But that does suggest a possible application for sound refraction - One
effect is changing the direction of sound waves in addition to difusing
them. Chose only the direction change aspect and you might end up
curving sounds around corners. Sort of like how electricity works in a
wire.

How useful this would be giviwn how easy it is to build a sound wave
guide that is based on reflection I can't say. Sometimes it's fun to
build a project that uses an aspect of nature and the motivation does
not need to go deeper. Other times such a project leads to practical
applications.


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On Apr 20, 7:48*pm, RichD wrote:
This may be a dumb question, I never studied acoustics....

If you look into the wrong end of a telescope,
everything looks reduced, 'anti-magnified'.
Is there anything analogous acoustically?

In both cases, the phenomena is described
by wave equations -

--
Rich


Acoustic imagery is exactly analogous to light imagery except that
having longitudinal waves there is no polarization affect.

The long wavelength makes diffraction much more dominant that for
light. Materials also have much greater dispersion over audible
frequencies.

Lenses tend to be difficult to demonstrate compared to mirrors due to
the large impedance mismatch to air. However, for a very limited
bandwidth an interested demonstrator could easily be made using layers
of less dense materials to build up an anti reflection coating. This
should not be too difficult due to the long wavelengths involved.
This is a demonstration I've always wanted to make but never had the
time.

http://richardfisher.com/
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On 4/20/2011 10:48 PM, RichD wrote:
This may be a dumb question, I never studied acoustics....

If you look into the wrong end of a telescope,
everything looks reduced, 'anti-magnified'.
Is there anything analogous acoustically?

In both cases, the phenomena is described
by wave equations -

--
Rich

How about an amphitheater like the Hollywood bowl.
Audience members are effectively at the 'anti-magnified'
wrong end of that acoustic telescope. That's about the
closest analogy I can think of at the moment.


Later...
Ron Capik
--
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On Wed, 20 Apr 2011 19:48:46 -0700 (PDT), RichD
wrote:

This may be a dumb question, I never studied acoustics....

If you look into the wrong end of a telescope,
everything looks reduced, 'anti-magnified'.
Is there anything analogous acoustically?

In both cases, the phenomena is described
by wave equations -


It is completely analogous. A telescope makes things look closer. A
directional microphone makes things sound closer.

If you look through a telescope the wrong way, things look further
away. If you point a directional microphone the wrong way, things
sound further away.

d
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Default audio telescope?

Hmm, the size of the observed image isn't directly related to
the nature of light waves emanating from them. The closest analogy
I can think of is the following... when you get your vision tested,
you go from large letters down to small letters. When you get
your hearing tested, you go from loud sounds to increasingly
quiet sounds (ignoring pitch and color blindness). So by that
analogy, running the sound through an attenuator rather than
through an amplifier would be one thought.

In rec.audio.tech RichD wrote:
: This may be a dumb question, I never studied acoustics....

: If you look into the wrong end of a telescope,
: everything looks reduced, 'anti-magnified'.
: Is there anything analogous acoustically?

: In both cases, the phenomena is described
: by wave equations -

: --
: Rich
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On Apr 21, 1:10*pm, Helpful person wrote:

Acoustic imagery is exactly analogous to light imagery except that
having longitudinal waves there is no polarization affect.

The long wavelength makes diffraction much more dominant that for
light. *Materials also have much greater dispersion over audible
frequencies.

Lenses tend to be difficult to demonstrate compared to mirrors due to
the large impedance mismatch to air. *However, for a very limited
bandwidth an interested demonstrator could easily be made using layers
of less dense materials to build up an anti reflection coating. *This
should not be too difficult due to the long wavelengths involved.
This is a demonstration I've always wanted to make but never had the
time.

http://richardfisher.com/


Richard has it exactly. Except for polarization sound waves do
exhibit wave actions analogous to light.

I'm sorry but loud and soft is NOT analogous to large and small
images! There is such a thing as audio imaging. Go talk to any
audiophile about his stereo setup. One really nifty setup using audio
imaging is to place your speakers back from a reflective wall aimed AT
the wall. In just the same way your image appears to be behind a
mirror, the "image" speakers will appear to your ears as being BEHIND
the wall as far as the real speakers are placed a distance in front of
the wall. This is an especially nifty trick for a movie screen.

As for Peter Webb being "bugged" since sound waves "aren't used for
imaging" I'd suggest you investigate how old shipwrecks are found on
the ocean floor. Yes, sound lenses are not especially practical to
build but they DO exist. For example a balloon filled with various
gasses create them. As someone noted, acoustic lenses are sometimes
used for dispersion on horn speakers. But sound mirrors are much
easier to build so that is the typical thing.




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On Apr 21, 10:10*am, Helpful person wrote:
On Apr 20, 7:48*pm, RichD wrote:

Acoustic imagery is exactly analogous to light imagery except that
having longitudinal waves there is no polarization affect.

The long wavelength makes diffraction much more dominant that for
light. *Materials also have much greater dispersion over audible
frequencies.

Lenses tend to be difficult to demonstrate compared to mirrors due to
the large impedance mismatch to air. *However, for a very limited
bandwidth an interested demonstrator could easily be made using layers
of less dense materials to build up an anti reflection coating. *This
should not be too difficult due to the long wavelengths involved.
This is a demonstration I've always wanted to make but never had the
time.

http://richardfisher.com/


This thread has got me interested again about acoustic lenses. Does
anyone here have a source for speed and dispersion of sound in common
materials? It seems to me that liquids (and metals) are of most
interest as neither are very lossy. (Hardwood may also be a cool
material to use.)

By the way, the intensity (or volume) of imaged sound is solely
dependent on the NA, just as in light.

http://richardfisher.com/
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"Don Pearce" wrote:
A telescope makes things look closer.
A directional microphone makes things sound closer.

hanson wrote:
Bull horns and loudspeakers are certainly NOT
audio telescopes as inferred by other posters.

A telescope, audio or video, is a passive instrument
that absorbs incoming info/energy, like these audio
gismos he
http://www.lilesnet.com/didjaknow/eardar/
"Eardar" (ahahaha..) just & then listen for the echo.

In/on a related issue, what is a
passive AUDIO MICROSCOPE and what does it do?


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In sci.physics Helpful person wrote:
On Apr 21, 10:10Â*am, Helpful person wrote:
On Apr 20, 7:48Â*pm, RichD wrote:

Acoustic imagery is exactly analogous to light imagery except that
having longitudinal waves there is no polarization affect.

The long wavelength makes diffraction much more dominant that for
light. Â*Materials also have much greater dispersion over audible
frequencies.

Lenses tend to be difficult to demonstrate compared to mirrors due to
the large impedance mismatch to air. Â*However, for a very limited
bandwidth an interested demonstrator could easily be made using layers
of less dense materials to build up an anti reflection coating. Â*This
should not be too difficult due to the long wavelengths involved.
This is a demonstration I've always wanted to make but never had the
time.

http://richardfisher.com/


This thread has got me interested again about acoustic lenses. Does
anyone here have a source for speed and dispersion of sound in common
materials? It seems to me that liquids (and metals) are of most
interest as neither are very lossy. (Hardwood may also be a cool
material to use.)

By the way, the intensity (or volume) of imaged sound is solely
dependent on the NA, just as in light.

http://richardfisher.com/


One little problem in all this is the human body doesn't have a senor that
can process imaged sound, only imaged light.

Nor is there anything that I know of analogous to photographic film for an
audio image.

Which leaves building something like a solid state video camera for audio.

One could build a 32X32 pixel audio imager with 1,024 cheap microphones
like these for $0.27 in quanties of 1,000:

http://www.mouser.com/catalog/specsheets/KT-400332.pdf

Follow those with a little amplification/buffering, a switch matrix, and
dump the output into a PC sound card with appropriate software.

And voila, you have an audio imager.


--
Jim Pennino

Remove .spam.sux to reply.
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Default audio telescope?

Acoustic imagery is exactly analogous to light imagery except that
having longitudinal waves there is no polarization affect.


Same analogies hold for optical and acoustic resonant cavities.

Whispering gallery modes are big in nano-optics right now. But they
started out, as the name indicates, in acoustics.
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"hanson" corrected ||| in
message ... & wrote:

"Don Pearce" wrote:
A telescope makes things look closer.
A directional microphone makes things sound closer.

hanson wrote:
Bull horns and loudspeakers are certainly NOT
audio telescopes as inferred by other posters.

A telescope, audio or video, is a passive instrument
that absorbs incoming info/energy, like these audio
gismos he
http://www.lilesnet.com/didjaknow/eardar/
||| "Eardar" (ahahaha..) just listens for noise while
||| "radar" "radio-yells" & then listens for the echo.

In/on a related issue, what is a
passive AUDIO MICROSCOPE and what does it do?




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On Thu, 21 Apr 2011 18:26:54 -0700, "hanson" wrote:

"hanson" corrected ||| in
message ... & wrote:

"Don Pearce" wrote:
A telescope makes things look closer.
A directional microphone makes things sound closer.

hanson wrote:
Bull horns and loudspeakers are certainly NOT
audio telescopes as inferred by other posters.

A telescope, audio or video, is a passive instrument
that absorbs incoming info/energy, like these audio
gismos he
http://www.lilesnet.com/didjaknow/eardar/
||| "Eardar" (ahahaha..) just listens for noise while
||| "radar" "radio-yells" & then listens for the echo.

In/on a related issue, what is a
passive AUDIO MICROSCOPE and what does it do?


The threading has confused me. The bits that start with "Hanson Wrote"
- are they quotes from earlier posts by you? How does that work?

If you are just replying, please omit that pre-amble. The news system
makes it clear without that.

d
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"Don Pearce" wrote:
"hanson" corrected ||| in
message ... & wrote:
hanson wrote:
"Don Pearce" wrote:
------------
Don, above is what you call the Preamble.
Most of the time I put it there to show who
did partake in the discussion that follows.
------------

"Don Pearce" wrote:
A telescope makes things look closer.
A directional microphone makes things sound closer.

hanson wrote:
Bull horns and loudspeakers are certainly NOT
audio telescopes as inferred by other posters.

A telescope, audio or video, is a passive instrument
that absorbs incoming info/energy, like these audio
gismos he
http://www.lilesnet.com/didjaknow/eardar/
||| "Eardar" (ahahaha..) just listens for noise while
||| "radar" "radio-yells" & then listens for the echo.

In/on a related issue, what is a
passive AUDIO MICROSCOPE and what does it do?

"Don Pearce" wrote:
The threading has confused me. The bits that start with
"Hanson Wrote" - are they quotes from earlier posts by
you? How does that work?
If you are just replying, please omit that pre-amble.
The news system makes it clear without that.

hanson wrote:
.... ahahaha... it does not matter whether it says
"wrote" or "writes"... By the time you read it, it IS
a "wrote", n'est pas... ahahahaah...

Don, there are all kinds of new readers, each with
a different format, and then there are poster who
mangle the threads, switch topic & suject lines...

When I reply, or OP, I always put in
== "Poster's name" wrote: ==
with the intent to ID who said what, because the
"" type system is not universal.

Some posters use "|||", others ":::" or no markers
at all. Google leaves in "Hyde text"; Still others
use a full line of "=========" or "---------------"

There is no uniform "news system, Don. Live with it,
besides, "An Eagle does not hunt fFies"... So, do
address the issue, instead of whining over format.
Thanks for the laughs, though... ahahahanson


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On Apr 21, 9:26*pm, "hanson" wrote:

A telescope makes things look closer.
A directional microphone makes things sound closer.


This is pretty much wrong. A telescope is an imaging device that
magnifies the image of distant objects. A directional microphone, on
the other hand, is a directional audio antenna. It is analogous to a
directional radio or other electromagnetic antenna, not a telescope.
One CAN however produce a map of some sonic source with one by
scanning it over the source and recording intensities.

Bull horns and loudspeakers are certainly NOT
audio telescopes as inferred by other posters.


True.

A telescope, audio or video, is a passive instrument
that absorbs incoming info/energy, like these audio
gismos he *
http://www.lilesnet.com/didjaknow/eardar/


I positively LOVE the old gadgets at this site! My all-time favorite
is the Dr. Seuss machine (the last one in the series of photos).
Thanks for the laughs, ha ha ha Hanson.

Note that these gadgets are directional microphones, NOT "audio
telescopes" even though they do map intensities of sources. Oh wait.
The exception would be the huge curved "mirrors" built on the coast.
These doubtless DO form sonic images of the source which can be
scanned by movable microphones or a huge array of them totally
analogous to a telescope where the image plane can be scanned with a
single photocell. The horn units do NOT form images.

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"Benj" wrote in message
...
On Apr 21, 9:26 pm, "hanson" wrote:

A telescope makes things look closer.
A directional microphone makes things sound closer.


This is pretty much wrong. A telescope is an imaging device that
magnifies the image of distant objects. A directional microphone, on
the other hand, is a directional audio antenna. It is analogous to a
directional radio or other electromagnetic antenna, not a telescope.
One CAN however produce a map of some sonic source with one by
scanning it over the source and recording intensities.

Bull horns and loudspeakers are certainly NOT
audio telescopes as inferred by other posters.


True.

A telescope, audio or video, is a passive instrument
that absorbs incoming info/energy, like these audio
gismos he
http://www.lilesnet.com/didjaknow/eardar/


I positively LOVE the old gadgets at this site! My all-time favorite
is the Dr. Seuss machine (the last one in the series of photos).
Thanks for the laughs, ha ha ha Hanson.

Note that these gadgets are directional microphones, NOT "audio
telescopes" even though they do map intensities of sources. Oh wait.
The exception would be the huge curved "mirrors" built on the coast.
These doubtless DO form sonic images of the source which can be
scanned by movable microphones or a huge array of them totally
analogous to a telescope where the image plane can be scanned with a
single photocell. The horn units do NOT form images.

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"Benj" wrote:
"hanson" wrote:
"Don Pearce" wrote:




"Don Pearce" [1] wrote:
A telescope makes things look closer.
A directional microphone makes things sound closer.

"Benj" wrote:
This is pretty much wrong. A telescope is an imaging device that
magnifies the image of distant objects. A directional microphone, on
the other hand, is a directional audio antenna. It is analogous to a
directional radio or other electromagnetic antenna, not a telescope.
One CAN however produce a map of some sonic source with one by
scanning it over the source and recording intensities.

"hanson" wrote:
Bull horns and loudspeakers are certainly NOT
audio telescopes as inferred by other posters.

"Benj" wrote:
True.

"hanson" wrote:
A telescope, audio or video, is a passive instrument
that absorbs incoming info/energy, like these audio
gismos he
http://www.lilesnet.com/didjaknow/eardar/

"Benj" wrote:
I positively LOVE the old gadgets at this site! My all-time favorite
is the Dr. Seuss machine (the last one in the series of photos).
Thanks for the laughs, ha ha ha Hanson.

Note that these gadgets are directional microphones, NOT "audio
telescopes" even though they do map intensities of sources. Oh wait.
The exception would be the huge curved "mirrors" built on the coast.
These doubtless DO form sonic images of the source which can be
scanned by movable microphones or a huge array of them totally
analogous to a telescope where the image plane can be scanned with a
single photocell. The horn units do NOT form images.

hanson wrote:
.... ahahaha.. Well, Jacoby, one can nit-pick the meaning
of any subject line apart, to fit and satisfy one's own whims
and agenda. The classic example is of course is Relativity.
Good talking to your. Happy Passah/Easter to you, Ben,
... and thanks for the laughs... ahahaha... ahahanson

PS:
A few posters recently cranked themselves over my
style of "quoting" without specifying what "quoting" was.
I wonder now.
In the post I got from you, on my OE 6, the line:
="Don Pearce" [1] wrote: =
did NOT appear.
I now **added** this [1] line, because without it seems
that I, hanson, said what was actually expressed by Don.

Did you NOT receive [1], or did you omit line [1]?
Is that the issue that those other folks have bitched about?





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On Thu, 21 Apr 2011 16:29:55 -0700 (PDT), Helpful person wrote:

On Apr 21, 10:10*am, Helpful person wrote:
On Apr 20, 7:48*pm, RichD wrote:

Acoustic imagery is exactly analogous to light imagery except that
having longitudinal waves there is no polarization affect.

The long wavelength makes diffraction much more dominant that for
light. *Materials also have much greater dispersion over audible
frequencies.

Lenses tend to be difficult to demonstrate compared to mirrors due to
the large impedance mismatch to air. *However, for a very limited
bandwidth an interested demonstrator could easily be made using layers
of less dense materials to build up an anti reflection coating. *This
should not be too difficult due to the long wavelengths involved.
This is a demonstration I've always wanted to make but never had the
time.

http://richardfisher.com/


This thread has got me interested again about acoustic lenses. Does
anyone here have a source for speed and dispersion of sound in common
materials? It seems to me that liquids (and metals) are of most
interest as neither are very lossy. (Hardwood may also be a cool
material to use.)

By the way, the intensity (or volume) of imaged sound is solely
dependent on the NA, just as in light.

http://richardfisher.com/



Seems to be for ultrasonics, but of possible interest:
http://www.3dguys.com/acoustography.php

Acoustic images can be formed by simple shadow casting (analogous to
radiography) or with acoustic lenses (analogous to photography or
videography). In the through-transmission shadow mode of acoustography
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RichD RichD is offline
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On Apr 21, AES wrote:
I was once shown, some years ago, an "acoustic laser"
Two large (half-meter diameter) curved metal mirrors (like
shallow woks), spaced maybe two meters apart on an optical
table to form an acoustic resonator. *In the middle a chunk of
"acoustic laser material" consisting of a little
match-box sized box with an omnidirectional microphone at
each end, with each of these connected through a tiny
transistor audio amp to a small speaker on the opposite end.

Took up a lot of table space -- but "lased" nicely.


Sounds nifty, but I'm unclear on the concept of
acoustic laser - what is the definition, what
did you observe?

--
Rich
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Skywise Skywise is offline
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wrote in :

Which leaves building something like a solid state video camera for
audio.

One could build a 32X32 pixel audio imager with 1,024 cheap microphones
like these for $0.27 in quanties of 1,000:

http://www.mouser.com/catalog/specsheets/KT-400332.pdf

Follow those with a little amplification/buffering, a switch matrix, and
dump the output into a PC sound card with appropriate software.

And voila, you have an audio imager.


With this design you'd need an audio input for every microphone.
A typical sound card only has 2 inputs (stereo) so you'd need
512 audio cards. And then processing all those signals? Yikes!

Rather, have a microcontroller scan your 1024 inputs and send
the values to the PC via USB, where software then assembles the
input into an image.

OH, very important point. Each pixel would be generating a value
based on sound volume. Frequency would have to be discarded, so
this would be a 'monochrome camera'. You could expand to three
inputs for each pixel with each of a different bandwidth, then
that could give you 'color' when represented as RGB.

Brian
--
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism
Seismic FAQ: http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html
Quake "predictions": http://www.skywise711.com/quakes/EQDB/index.html
Sed quis custodiet ipsos Custodes?
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Peter Webb Peter Webb is offline
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Default audio telescope?


"Skywise" wrote in message
...
wrote in :

Which leaves building something like a solid state video camera for
audio.

One could build a 32X32 pixel audio imager with 1,024 cheap microphones
like these for $0.27 in quanties of 1,000:

http://www.mouser.com/catalog/specsheets/KT-400332.pdf

Follow those with a little amplification/buffering, a switch matrix, and
dump the output into a PC sound card with appropriate software.

And voila, you have an audio imager.


With this design you'd need an audio input for every microphone.
A typical sound card only has 2 inputs (stereo) so you'd need
512 audio cards. And then processing all those signals? Yikes!

Rather, have a microcontroller scan your 1024 inputs and send
the values to the PC via USB, where software then assembles the
input into an image.

OH, very important point. Each pixel would be generating a value
based on sound volume. Frequency would have to be discarded, so
this would be a 'monochrome camera'. You could expand to three
inputs for each pixel with each of a different bandwidth, then
that could give you 'color' when represented as RGB.


Disagree. You could measure the sound pressure wave, which will give you
frequency information.

Indeed, I suspect that you would have to anyway, for a couple of reasons:

1. If you just try and measure average intensity from each mike over some
period, you are effectively sticking in a bandpass filter which removes high
frequencies, which is where most of the directional information comes from.

2. The cheapest/easiest/most effective of building such a device is by
attaching them to a flat surface (eg a wall) and use it is as a phased array
(eliminates mirrors and lenses and the attenuation and distortion they
create). This will require the baseband signals to be correlated.

I think you could actually build a very accurate imaging device in this
manner. If you place the microphones (say) 10 metres apart, you should get a
resolution at 10 kHz of about 1/100 of a radian. Same principle as used in
radio astronomy when linking radio-telecopes seperate by a large distance to
improve resolution.



Brian
--
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism
Seismic FAQ: http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html
Quake "predictions": http://www.skywise711.com/quakes/EQDB/index.html
Sed quis custodiet ipsos Custodes?


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Default audio telescope?

In sci.physics Skywise wrote:
wrote in :

Which leaves building something like a solid state video camera for
audio.

One could build a 32X32 pixel audio imager with 1,024 cheap microphones
like these for $0.27 in quanties of 1,000:

http://www.mouser.com/catalog/specsheets/KT-400332.pdf

Follow those with a little amplification/buffering, a switch matrix, and
dump the output into a PC sound card with appropriate software.

And voila, you have an audio imager.


With this design you'd need an audio input for every microphone.
A typical sound card only has 2 inputs (stereo) so you'd need
512 audio cards. And then processing all those signals? Yikes!


No, you don't.

You make up a switch with 16 16-1 FET mux chips and a little logic to
make either a single 1024-1 switch and feed it into one channel of a PC
sound card or 2 512-1 switches and feed it into the L-R channels of a
2 channel sound card.

Rather, have a microcontroller scan your 1024 inputs and send
the values to the PC via USB, where software then assembles the
input into an image.


Show me the microcontroller that has 1024 analog inputs.

That's why you build the switching, to scan the microphone outputs.

OH, very important point. Each pixel would be generating a value
based on sound volume. Frequency would have to be discarded,


No, it wouldn't.

What the hell do you think a sound card processes?

You get all of amplitude, frequency, and phase.

so
this would be a 'monochrome camera'. You could expand to three
inputs for each pixel with each of a different bandwidth, then
that could give you 'color' when represented as RGB.


Or you could just analyze the frequency information from the microphones
with the sound card and have an essentially infinite number of "colors".



--
Jim Pennino

Remove .spam.sux to reply.


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Default audio telescope?

In sci.physics Peter Webb wrote:

"Skywise" wrote in message
...
wrote in :

Which leaves building something like a solid state video camera for
audio.

One could build a 32X32 pixel audio imager with 1,024 cheap microphones
like these for $0.27 in quanties of 1,000:

http://www.mouser.com/catalog/specsheets/KT-400332.pdf

Follow those with a little amplification/buffering, a switch matrix, and
dump the output into a PC sound card with appropriate software.

And voila, you have an audio imager.


With this design you'd need an audio input for every microphone.
A typical sound card only has 2 inputs (stereo) so you'd need
512 audio cards. And then processing all those signals? Yikes!

Rather, have a microcontroller scan your 1024 inputs and send
the values to the PC via USB, where software then assembles the
input into an image.

OH, very important point. Each pixel would be generating a value
based on sound volume. Frequency would have to be discarded, so
this would be a 'monochrome camera'. You could expand to three
inputs for each pixel with each of a different bandwidth, then
that could give you 'color' when represented as RGB.


Disagree. You could measure the sound pressure wave, which will give you
frequency information.


A PC sound card will give you anything you want from the microphones and
you have frequecy, amplitude, and phase available for analysis.

Indeed, I suspect that you would have to anyway, for a couple of reasons:

1. If you just try and measure average intensity from each mike over some
period, you are effectively sticking in a bandpass filter which removes high
frequencies, which is where most of the directional information comes from.

2. The cheapest/easiest/most effective of building such a device is by
attaching them to a flat surface (eg a wall) and use it is as a phased array
(eliminates mirrors and lenses and the attenuation and distortion they
create). This will require the baseband signals to be correlated.


And it becomes a phased array via software running on the sound card.

I think you could actually build a very accurate imaging device in this
manner. If you place the microphones (say) 10 metres apart, you should get a
resolution at 10 kHz of about 1/100 of a radian. Same principle as used in
radio astronomy when linking radio-telecopes seperate by a large distance to
improve resolution.



--
Jim Pennino

Remove .spam.sux to reply.
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Skywise Skywise is offline
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Default audio telescope?

"Peter Webb" wrote in
u:


"Skywise" wrote in message
...
wrote in
:

Which leaves building something like a solid state video camera for
audio.

One could build a 32X32 pixel audio imager with 1,024 cheap
microphones like these for $0.27 in quanties of 1,000:

http://www.mouser.com/catalog/specsheets/KT-400332.pdf

Follow those with a little amplification/buffering, a switch matrix,
and dump the output into a PC sound card with appropriate software.

And voila, you have an audio imager.


With this design you'd need an audio input for every microphone.
A typical sound card only has 2 inputs (stereo) so you'd need
512 audio cards. And then processing all those signals? Yikes!

Rather, have a microcontroller scan your 1024 inputs and send
the values to the PC via USB, where software then assembles the
input into an image.

OH, very important point. Each pixel would be generating a value
based on sound volume. Frequency would have to be discarded, so
this would be a 'monochrome camera'. You could expand to three
inputs for each pixel with each of a different bandwidth, then
that could give you 'color' when represented as RGB.


Disagree. You could measure the sound pressure wave, which will give you
frequency information.

Indeed, I suspect that you would have to anyway, for a couple of
reasons:

1. If you just try and measure average intensity from each mike over
some period, you are effectively sticking in a bandpass filter which
removes high frequencies, which is where most of the directional
information comes from.

2. The cheapest/easiest/most effective of building such a device is by
attaching them to a flat surface (eg a wall) and use it is as a phased
array (eliminates mirrors and lenses and the attenuation and distortion
they create). This will require the baseband signals to be correlated.

I think you could actually build a very accurate imaging device in this
manner. If you place the microphones (say) 10 metres apart, you should
get a resolution at 10 kHz of about 1/100 of a radian. Same principle as
used in radio astronomy when linking radio-telecopes seperate by a large
distance to improve resolution.


I do not disagree with what you describe, but you described a completely
different method than what was originally proposed, which was to use
acoustic lenses and mirrors to form an image. Phased array has no need
for these structures.

Brian
--
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism
Seismic FAQ: http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html
Quake "predictions": http://www.skywise711.com/quakes/EQDB/index.html
Sed quis custodiet ipsos Custodes?
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Skywise Skywise is offline
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I think there is a misunderstanding, perhaps on my part, of what
is being "imaged". Can we go back to that and describe what is meant
to make sure we are on the same page? I thought we were talking
about an almost literal "image" in the sense of optics and light,
except using sound to convey the information, and that we would
end up with a "picture" on a screen. In that sense I see each pixel,
for example, representing the intensity of sound in a specific
direction, just as in a picture each pixel represents the brightness
in a specific direction.

BTW, could you please leave the crossposts on the followup? It
appears you are hailing from sci.physics, but since the OP
crossposted, there are now participants from other groups such
as myself. I know there are arguments against crossposting, but
since it's been done we might as well leave it in order to keep
the conversation from breaking up.

Brian
--
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism
Seismic FAQ: http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html
Quake "predictions": http://www.skywise711.com/quakes/EQDB/index.html
Sed quis custodiet ipsos Custodes?
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[email protected] jimp@specsol.spam.sux.com is offline
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Default audio telescope?

In sci.physics Skywise wrote:
I think there is a misunderstanding, perhaps on my part, of what
is being "imaged". Can we go back to that and describe what is meant
to make sure we are on the same page? I thought we were talking
about an almost literal "image" in the sense of optics and light,
except using sound to convey the information, and that we would
end up with a "picture" on a screen. In that sense I see each pixel,
for example, representing the intensity of sound in a specific
direction, just as in a picture each pixel represents the brightness
in a specific direction.


Direction has little to nothing to do with it.

Each pixel in an image represents the amplitudes of some set of frequencies
of the image.

An image is an image, whether it is formed from the visiable spectrum,
IR, UV, microwave, or sound.

BTW, could you please leave the crossposts on the followup?


Nope.

It
appears you are hailing from sci.physics,


Yep.

crossposted, there are now participants from other groups such
as myself.


So ignore the Followup-To: header.


--
Jim Pennino

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Randy Yates Randy Yates is offline
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On 04/20/2011 10:48 PM, RichD wrote:
This may be a dumb question, I never studied acoustics....

If you look into the wrong end of a telescope,
everything looks reduced, 'anti-magnified'.
Is there anything analogous acoustically?

In both cases, the phenomena is described
by wave equations -


Rich,

The common telescope is a device that is "bidirectional", i.e., it "processes"
light both ways, and either end can be used as receiver or transmitter.

"Audio telescopes" are more likely to operate electronically and are
thus "unidirectional," so you don't have the ability to reverse
input and output function.
--
Randy Yates % "So now it's getting late,
Digital Signal Labs % and those who hesitate
% got no one..."
http://www.digitalsignallabs.com % 'Waterfall', *Face The Music*, ELO


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"Randy Yates" wrote in message
m...
| On 04/20/2011 10:48 PM, RichD wrote:
| This may be a dumb question, I never studied acoustics....
|
| If you look into the wrong end of a telescope,
| everything looks reduced, 'anti-magnified'.
| Is there anything analogous acoustically?
|
| In both cases, the phenomena is described
| by wave equations -
|
| Rich,
|
| The common telescope is a device that is "bidirectional", i.e., it
"processes"
| light both ways, and either end can be used as receiver or transmitter.
|
| "Audio telescopes" are more likely to operate electronically and are
| thus "unidirectional," so you don't have the ability to reverse
| input and output function.

Obviously you've never heard of a telephone.



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On Apr 26, 9:53*am, Randy Yates wrote:

Rich,

The common telescope is a device that is "bidirectional", i.e., it "processes"
light both ways, and either end can be used as receiver or transmitter.

"Audio telescopes" are more likely to operate electronically and are
thus "unidirectional," so you don't have the ability to reverse
input and output function.
--

Not true. Neither the receiver (compare with camera) nor the audio
source (compare with illumination) are part of the telescope.

http://richardfisher.com/
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On 04/26/2011 02:44 PM, Helpful person wrote:
On Apr 26, 9:53 am, Randy wrote:

Rich,

The common telescope is a device that is "bidirectional", i.e., it "processes"
light both ways, and either end can be used as receiver or transmitter.

"Audio telescopes" are more likely to operate electronically and are
thus "unidirectional," so you don't have the ability to reverse
input and output function.
--

Not true. Neither the receiver (compare with camera) nor the audio
source (compare with illumination) are part of the telescope.


You're right: "receiver" and "transmitter" were the wrong terms. Substitute
"input" and "output," respectively.

However, this was a terminology issue; the basic point was sound (no pun
intended).
--
Randy Yates % "So now it's getting late,
Digital Signal Labs % and those who hesitate
% got no one..."
http://www.digitalsignallabs.com % 'Waterfall', *Face The Music*, ELO
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On Tue, 26 Apr 2011 21:14:33 -0400, Randy Yates wrote:

On 04/26/2011 02:44 PM, Helpful person wrote:
On Apr 26, 9:53 am, Randy wrote:

Rich,

The common telescope is a device that is "bidirectional", i.e., it
"processes" light both ways, and either end can be used as receiver or
transmitter.

"Audio telescopes" are more likely to operate electronically and are
thus "unidirectional," so you don't have the ability to reverse input
and output function.
--

Not true. Neither the receiver (compare with camera) nor the audio
source (compare with illumination) are part of the telescope.


You're right: "receiver" and "transmitter" were the wrong terms.
Substitute "input" and "output," respectively.

However, this was a terminology issue; the basic point was sound (no pun
intended).


Indeed earlier posts in this thread concerned the refraction of sound.

Sure, just as with an optical telescope one can invert such apparatus,
i.e. "reverse its inputs and outputs", with about the result one might
expect, just as one can do with apparatus which focuses sound by
reflecting it.

Not sure why you'd do it, having peered through the objective lens of a
telescope before.... [grin]

-- RLW
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Default audio telescope?


"AES" wrote in message
...
Hello.

If anyone wants to investigate acoustic mirrors then have a look at :

http://www.andrewgrantham.co.uk/soundmirrors/



Nice!!

I was once shown, some years ago, an "acoustic laser" (maybe at the
University of Maryland Baltimore County campus??): Two large
(half-meter diameter) curved metal mirrors (like shallow woks, or the
curved metal dishes kids slide down snowbanks on), spaced maybe two
meters apart on an optical table to form an acoustic resonator. In the
middle a chunk of "acoustic laser material" consisting of a little
match-box sized box with an omnidirectional microphone at each end, with
each of these connected through a tiny transistor audio amp to a small
speaker on the opposite end.

Took up a lot of table space -- but "lased" nicely.


What do you mean by "lase" in this context? "sase"? s for sound?

Could soundwaves be made highly directional also?

Thanks

I remember some bizarre experiment being reported in New Scientist"
a very long time ago about two guys messing up with something which
from the description appeared to be an "acoustic laser" indeed and one
of the experimenters getting killed by the contraption.

(perhaps from something else entirely, i.e. not having anything to do with
intense sound waves.)


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