acoustics

[Androcles]

"Rich Grise" <rich@example.net> wrote in message
news:HGAcj.83626$GV4.20532@trnddc05...
: On Tue, 25 Dec 2007 15:30:57 +0000, Androcles wrote:
: > "BobG" <bobgardner@aol.com> wrote in message
: >
: > : If they were having a conversation, they were conversing, not :
: > conversating.
: >
: > On the other hand, there are five metacarpals. The other side of the
: > coin is the obverse, not the reverse or the converse.
:
: No, actually, the obverse is the "front" of the coin, usually considered
: to be "heads", and the "tails" side is the reverse.
:
: Hope This Helps!

No, in fact, observe the other side is the inside and conversely
has a reversed head on the reverse and a converse tail on
the reverse of the obverse.
Hope that is declarified.

 

[Don Klipstein]

In article <3ku4n3lqc9r463rcuoi1k8b6pbhu2avctv@4ax.com>, John Larkin wrote:

On Tue, 25 Dec 2007 09:34:20 -0500, "Ethan Winer" <ethanw at
ethanwiner dot com> wrote:

Rich,

'I see you, you see me' is pretty much a universal law.

Not if I'm in the dark, and you're in the sun. Or if I'm hiding in the
bushes and you're not. Or if I have a telescope but you don't.

I thought this refers to a principle that when a ray is traced from
origin to destination, percentage loss at each lossy point are the same in
both directions, percentage reflected by partially reflective objects
in the way is the same for both directions, and percentage making it from
origin to destination are the same in both directions.

Of course, polarizers and polarized light can complicate this, but we
can't have a situation where there is a container that light can enter but
not exit along the same path in a way that allows a thermal radiator to
heat a target in the container to a higher temperature than the thermal
radiator is at.

- Don Klipstein (don@misty.com)

 

[Sjouke Burry]

Androcles wrote:

"Rich Grise" <rich@example.net> wrote in message
news:HGAcj.83626$GV4.20532@trnddc05...
: On Tue, 25 Dec 2007 15:30:57 +0000, Androcles wrote:
: > "BobG" <bobgardner@aol.com> wrote in message
:
: > : If they were having a conversation, they were conversing, not :
: > conversating.
:
: > On the other hand, there are five metacarpals. The other side of the
: > coin is the obverse, not the reverse or the converse.
:
: No, actually, the obverse is the "front" of the coin, usually considered
: to be "heads", and the "tails" side is the reverse.
:
: Hope This Helps!

No, in fact, observe the other side is the inside and conversely
has a reversed head on the reverse and a converse tail on
the reverse of the obverse.
Hope that is declarified.


They do have pills for what ails you.

In the mean time: stay calm.

 

[Androcles]

"Sjouke Burry" <burrynulnulfour@ppllaanneett.nnlll> wrote in message
news:4772f6e1$0$25482$ba620dc5@text.nova.planet.nl...
: Androcles wrote:
: > "Rich Grise" <rich@example.net> wrote in message
: > news:HGAcj.83626$GV4.20532@trnddc05...
: > : On Tue, 25 Dec 2007 15:30:57 +0000, Androcles wrote:
: > : > "BobG" <bobgardner@aol.com> wrote in message
: > : >
: > : > : If they were having a conversation, they were conversing, not :
: > : > conversating.
: > : >
: > : > On the other hand, there are five metacarpals. The other side of the
: > : > coin is the obverse, not the reverse or the converse.
: > :
: > : No, actually, the obverse is the "front" of the coin, usually
considered
: > : to be "heads", and the "tails" side is the reverse.
: > :
: > : Hope This Helps!
: >
: > No, in fact, observe the other side is the inside and conversely
: > has a reversed head on the reverse and a converse tail on
: > the reverse of the obverse.
: > Hope that is declarified.
: >
: >
: They do have pills for what ails you.
: In the mean time: stay calm.

Nah, I just ignore fuckheaded trolls like you that are not amused
by a simple play on words you are incapable of understanding
and rely on insult for their kicks. Piss off, you fucking moron.
*plonk*

 

[Bob Masta]

On Wed, 26 Dec 2007 09:01:06 -0500, "Ethan Winer" <ethanw at
ethanwiner dot com> wrote:

Bob,

The output is not "focused" in the same sense as when the dish is used as
a collector

Yes, but the person away from the collector isn't a "large" source either.
So it still seems it would be 100 percent reciprocal, no?

This is like half of a pair of reflectors like you see in parks, where two
people can be hundreds of yards away and talk as if they're next to each
other.

You have given the answer in your example: If one reflector was all
it took to get 100% reciprocal operation, then they wouldn't use
two reflectors.

Suppose we think of this with light beams instead of sound waves,
and use laser pointers so that we have a planar wave front. The
guy without a reflector can aim his beam at the distant reflector,
which might have an area of (say) 10 square feet, and anywhere
he aims within that area the beam will be captured and received
more-or-less 100% at the focal point. But the guy at the focal
point can't do the same thing in reverse. He either needs to aim
his beam *exactly* at the other guy (avoiding the reflector, or
bouncing it on a careful trajectory), or else he needs many, many
beams at slightly different trajectories so that they will cover
the same 10 square-foot area at full intensity at the reflectorless
guy's end.

Best regards,


Bob Masta

DAQARTA v3.50
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, FREE Signal Generator
Science with your sound card!

 

[Ethan Winer]

Bob,

If one reflector was all it took to get 100% reciprocal operation, then
they wouldn't use two reflectors.

I don't think that follows. With only one reflector, the gain would be
insufficient for EITHER person to hear the other. Again, I'm not arguing too
strongly because I don't really know for sure. But so far I can't see why
it's not reciprocal.

The guy without a reflector can aim his beam at the distant reflector,
which might have an area of (say) 10 square feet, and anywhere he aims
within that area the beam will be captured and received more-or-less 100%
at the focal point.

Yes, but a person talking is not a beam.

--Ethan

 

[John Larkin]

On Wed, 26 Dec 2007 23:20:18 +0000 (UTC), don@manx.misty.com (Don
Klipstein) wrote:

In article <3ku4n3lqc9r463rcuoi1k8b6pbhu2avctv@4ax.com>, John Larkin wrote:
On Tue, 25 Dec 2007 09:34:20 -0500, "Ethan Winer" <ethanw at
ethanwiner dot com> wrote:

Rich,

'I see you, you see me' is pretty much a universal law.

Not if I'm in the dark, and you're in the sun. Or if I'm hiding in the
bushes and you're not. Or if I have a telescope but you don't.

I thought this refers to a principle that when a ray is traced from
origin to destination, percentage loss at each lossy point are the same in
both directions, percentage reflected by partially reflective objects
in the way is the same for both directions, and percentage making it from
origin to destination are the same in both directions.

Of course, polarizers and polarized light can complicate this, but we
can't have a situation where there is a container that light can enter but
not exit along the same path in a way that allows a thermal radiator to
heat a target in the container to a higher temperature than the thermal
radiator is at.

- Don Klipstein (don@misty.com)

There are optical isolators, like electrical isolators, that let light
go from port A to port B, but block light from B to A. They violate no
laws of thermodynamics, because they absorb the light from B, rather
than reflecting it.

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


John

 

[Richard Crowley]

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:glr8n3pvq5iiua9g6scdcg84vnobs4kuq9@4ax.com...

On Wed, 26 Dec 2007 23:20:18 +0000 (UTC), don@manx.misty.com (Don
Klipstein) wrote:

In article <3ku4n3lqc9r463rcuoi1k8b6pbhu2avctv@4ax.com>, John Larkin
wrote:
On Tue, 25 Dec 2007 09:34:20 -0500, "Ethan Winer" <ethanw at
ethanwiner dot com> wrote:

Rich,

'I see you, you see me' is pretty much a universal law.

Not if I'm in the dark, and you're in the sun. Or if I'm hiding in the
bushes and you're not. Or if I have a telescope but you don't.

I thought this refers to a principle that when a ray is traced from
origin to destination, percentage loss at each lossy point are the same in
both directions, percentage reflected by partially reflective objects
in the way is the same for both directions, and percentage making it from
origin to destination are the same in both directions.

Of course, polarizers and polarized light can complicate this, but we
can't have a situation where there is a container that light can enter but
not exit along the same path in a way that allows a thermal radiator to
heat a target in the container to a higher temperature than the thermal
radiator is at.

- Don Klipstein (don@misty.com)

There are optical isolators, like electrical isolators, that let light
go from port A to port B, but block light from B to A. They violate no
laws of thermodynamics, because they absorb the light from B, rather
than reflecting it.

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

Or just watch them interviewing the suspects on Law & Order

 

[Bob Masta]

On Thu, 27 Dec 2007 11:51:39 -0500, "Ethan Winer" <ethanw at
ethanwiner dot com> wrote:

Bob,

If one reflector was all it took to get 100% reciprocal operation, then
they wouldn't use two reflectors.

I don't think that follows. With only one reflector, the gain would be
insufficient for EITHER person to hear the other. Again, I'm not arguing too
strongly because I don't really know for sure. But so far I can't see why
it's not reciprocal.

The guy without a reflector can aim his beam at the distant reflector,
which might have an area of (say) 10 square feet, and anywhere he aims
within that area the beam will be captured and received more-or-less 100%
at the focal point.

Yes, but a person talking is not a beam.

The reflector provides gain for the listener, by concentrating the
sound from a large area down to a small area at his ear. Let's
say that the reflector is 10 square feet, so all sound impinging
on that area is concentrated down to his ear due to the nature
of the parabolic shape. The gain of this operation could easily
be 100:1 if the ear catches only 0.1 square foot.

Now when we turn around and speak into the reflector
it *spreads* the sound from the small source (mouth) over
that same 10 square feet. Is there gain here? Yes, but
not the same as the prior case: Here the only gain (as far
as the guy at the other end without a reflector is concerned) is
due to the fact that without the reflector the sound would be
a spherical source from the mouth, falling off with the square
of distance. With the reflector, assuming everything was just
right, the best you could hope for would be sound that was
collimated into a plane wave that did not fall off with distance.
But the sound would still be spread over 10 square feet in
the ideal case, and much more in reality. The ear of the listener on
the other end only catches a tiny percent of that without a
reflector. If his ear only catches 0.1 square foot, there is a *loss*
of 100:1 compared to having a reflector.

Best regards,


Bob Masta

DAQARTA v3.50
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, FREE Signal Generator
Science with your sound card!

 

[Ethan Winer]

Bob,

Let's say that the reflector is 10 square feet, so all sound impinging on
that area is concentrated down to his ear due to the nature of the
parabolic shape. The gain of this operation could easily be 100:1 if the
ear catches only 0.1 square foot.

Yes, but my point is that the source / person is not 10 square feet!

--Ethan

 

On Dec 28, 10:46 am, "Ethan Winer" <ethanw at ethanwiner dot com>
wrote:

Bob,

Let's say that the reflector is 10 square feet, so all sound impinging on
that area is concentrated down to his ear due to the nature of the
parabolic shape. The gain of this operation could easily be 100:1 if the
ear catches only 0.1 square foot.

Yes, but my point is that the source / person is not 10 square feet!

So far, everyone is making a bunch of assumptions,
many of which simply don't hold, with the result being
that the conclusions people are reaching are HIGHLY
suspect.

For example:

1. A parbolic reflector, has TWO focal points. If the
source or receiver is placed at the principle focal
point, the other focal point is an infinite distance
away and the system then will focus an incoming
set of parallel rays to the focal point and vice versa.
Move the focal point farther from the principle point,
and the other focal point now moves closer to the
system and the incoming/outgoing rays are no
longer parallel, but convergent.

Asserting that a parabolic disk will focus a set of
parallel rays to a small point ASSUME that the source
or receiver is placed at the infinity focus point of the
parabola.

A reciprocal transmitter-receiver system would
consist of two parabolic reflectors, with the
transmitter and receiver placed at the principle
focus of each reflector. The transmitter would
emit a parallel bundle of rays which the receiver
could refocus back to the focal point again.

BUT, a system does not REQUIRE a reciprocal
physical arrangement. You could have, say, a
transmitter with no reflector placed 100 feet away
and a receiver with its reflectors aimed at it and the
receiver moved out somewhat to compensate.

2. The ability of any such system to focus to a small
point is a function of the size of the reflector and
the wavelengths involved. With a reflector a few
FEET in diameter and wavelengths ranging from
several inches to many feet, the efficacy of a parabolic
reflector is limited. At low frequencies where the
wavelength is large compared to the dish, it simply
doesn't focus anything. At higher frequencies and
thus shrter wavelengths, the region of focus is,
essentially, defined by the wavelength. I.e. at say
1 kHz, you are simply NOT going to have any precision
in focusing smaller than a couple of feet at best.

 

[Benj]

On Dec 25, 3:25 pm, Uncle Al <Uncle...@hate.spam.net> wrote:

Whispering galleries and inside elliptic reflectors, yes. This is the
preferred way to build confessionals in church - at one focus - with
rentable scholarship rooms at the other focus.

Really? I"m going to have to look into this. I"m thinking I'd really
like to line up a few "scholarship" hours at peak confession times!

Parabolic reflector (satellite dish), not so much. Incoming will be
focused but outgoing will be collimated.

Obviously the "whispering gallery" setup would use TWO parabolic
reflectors which is the equivalent of the elliptic chamber. Both are
conic sections and work nearly the same. A single parabolic reflector
is the usual microphone setup. But a single reflector is the "I see
you, you see me" equivalent of only ONE person with a telescope as
opposed to each person having one. If both persons have similar
telescopes then that is the optical equivalent of a "whispering
chamber". And I might mention that acoustic lenses exist as well so a
reflector isn't essential to create the effects.

 

[Ethan Winer]

dpierce.cartchunk.org@gmail.com> wrote:

.... snip ...

Interesting stuff.
So with only one dish, is "I see you, you see me" true?

--Ethan

 

On Dec 29, 10:11 am, "Ethan Winer" <ethanw at ethanwiner dot com>
wrote:

dpierce.cartchunk....@gmail.com> wrote:

... snip ...

Interesting stuff.
So with only one dish, is "I see you, you see me" true?

Well, look at the optical analogy: with piece of equipment
available for under $5,000, you can see details on the moon
with a resolution on the order of a kilometer or less. But
the person standing on the moon without such an optical aid
couldn't even begin to resolve the county you live in.

It's a somewhat extreme example of the general case, but
going back to the acoustic equivalent, there is gain going in
both directions, but it is not entirely symmetrical. Assume
both "transmitters (i.e., persons speaking) radiate omni-
directionally. In the case of the speaker and no reflector,
the entire energy is emitted in all directions, and a far away
reflector intercepts only a very small portion of the radiated
power. However, the speaker is placed at the principle
focal point of the reflector, the reflector intercepts a much
larger portion of the total radiated power and collimates
it into a beam.

Imagine, for instance, a 1 meter diameter reflector and
the receiver and transmitter placed 30 meters apart.
In the former case, the reflector at the receiving end
intercepts only about 0.11% of the total radiated acoustic
power of the transmitter, whereas in the latter case, where
the focal length might be on the order of a half meter, it
intercepts maybe 30% of the energy.

However, the use of the reflector at the transmitter does
not, as assumed in the discussion, result in a collimated
beam with no divergence, for the reasons mentioned
previously. Rather, it, too, has divergence which is wave-
length and thus frequency dependent: more divergence
at lower frequencies than at high.

Be all that as it may, the result is more along the lines of
"I hear you a bit better than you hear me., or maybe not,
depends."

 

[Ethan Winer]

Be all that as it may, the result is more along the lines of
"I hear you a bit better than you hear me., or maybe not,
depends."

Thanks.

 

[syntheticwave]

On Dec 27 2007, 2:52 pm, NoS...@daqarta.com (Bob Masta) wrote:

On Wed, 26 Dec 2007 09:01:06 -0500, "Ethan Winer" <ethanw at

ethanwiner dot com> wrote:
Bob,

The output is not "focused" in the same sense as when the dish is used as
a collector

Yes, but the person away from the collector isn't a "large" source either..
So it still seems it would be 100 percent reciprocal, no?

This is like half of a pair of reflectors like you see in parks, where two
people can be hundreds of yards away and talk as if they're next to each
other.

You have given the answer in your example:  If one reflector was all
it took to get 100% reciprocal operation, then they wouldn't use
two reflectors.

Suppose we think of this with light beams instead of sound waves,
and use laser pointers so that we have a planar wave front.   The
guy without a reflector can aim his beam at the distant reflector,
which might have an area of (say) 10 square feet, and anywhere
he aims within that area the beam will be captured and received
more-or-less 100% at the focal point. But the guy at the focal
point can't do the same thing in reverse.  He either needs to aim
his beam *exactly* at the other guy (avoiding the reflector, or
bouncing it on a careful trajectory), or else he needs many, many
beams at slightly different trajectories so that they will cover
the same 10 square-foot area at full intensity at the reflectorless
guy's end.  

Best regards,

Bob Masta

              DAQARTA  v3.50
   Data AcQuisition And Real-Time Analysis
             www.daqarta.com
Scope, Spectrum, Spectrogram, FREE Signal Generator
        Science with your sound card!

In that connection seems a procedure interesting, restores acoustic
wave fronts according huygens principle:

http:www.syntheticwave.de

H.

 

[syntheticwave]

On Jan 16, 12:37 am, syntheticwave <hel...@googlemail.com> wrote:

In that connection seems a procedure interesting, restores acoustic
wave fronts according huygens principle:

http:www.syntheticwave.de

... possibly does not become clear from the link above alone, why
connected that animation with the topic "see I you, you see me"
discussed here. Therefore I would like to justify, what I want to
express by the link:
We must include the Huygens principle ( http://en.wikipedia.org/wiki/Huygens_principle
)
into the view of the topic. Thus acoustic waves can be bundled or
diverged or nearly at will aligned by the represented loudspeaker
field. Just suitably delay for each elementary wave would be need.
Perhaps that becomes clearer with the "acoustic curtain" animation:
http://www.syntheticwave.de/acoustic%20curtain.htm

With the light waves the conditions are alike in principle yet, but
both propagation speed and wavelength are by completely different
dimensions. If the light is not coherent, it hardly comes to
extinctions and overlays, as with the many longer acoustic waves the
case is. Therefore applies see I you, you normally sees me. But
whether I hear you, it depends on the fact how the elementary waves
superimpose.


Greetings Helmut, and sorry for my bad English ƒş