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Making It Loud?
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Brian Ravnaas
science forum beginner


Joined: 24 Mar 2005
Posts: 23

PostPosted: Thu Mar 24, 2005 10:04 pm    Post subject: Re: wall of water an effective sound barrier? Reply with quote

realizing that such a wall is not so likely to ever be built, but to
question my own statement above: what does anyone think about
replacing air in the cavity with water? i can imaginen it would be a
considerable task to dig into the math Sad((
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The Ghost
science forum Guru Wannabe


Joined: 24 Mar 2005
Posts: 115

PostPosted: Thu Mar 24, 2005 10:04 pm    Post subject: Re: Doppler Distortion & the "Anonymous Non-believer" Reply with quote

Bob Cain <arcane@arcanemethods.com> wrote in
news:ctv9ab0102h@enews1.newsguy.com:

Quote:


The Ghost wrote:


You did nothing meaningful, so there is nothing to refute. As per
the copy/paste of the post below, I am not alone in making that
assessment.

Refute the equation I derived or admit you can't.

There is nothing to refute. You derived nothing. You are a fraud.
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Guest






PostPosted: Thu Mar 24, 2005 10:04 pm    Post subject: Re: Removing hum from a recording Reply with quote

After giving it some thought, depending on how the intensity varies,
the affects may be more far reaching, and since the file is longer than
one second you will have to deal with fractional frequencies as well,
so I think ghosts advise, to do an FFT, is good, it's to bad he's
dead.
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Brian Ravnaas
science forum beginner


Joined: 24 Mar 2005
Posts: 23

PostPosted: Thu Mar 24, 2005 10:04 pm    Post subject: Re: Reverb room versus ETF Reply with quote

Ethan Winer wrote:
Quote:
Brian,


I don't see why the raw response matters, which is why I made the
point that
moving around the room changes the response but (apparently) not the
decay
rate. So even if the mike/speaker/room/whatever is down 10 dB at 40
Hz, the
difference between the peak level at t=0 and at t=1 second should
still
reflect the correct decay rate. At least that's how it seems to me.


For your tests, it doesn't matter at all. I had proposed estimating
room damping via the "3dB" method, and for that it would matter. So,
no, for your tests i haven't any concerns about it.

Quote:

I imagined creating a grid with a transparent background that has the
same
angled shape and aspect ratio as the ETF graph. Then in a graphics
program
it would be laid on top of the graph to provide a "floating" 3D grid.
It
wouldn't be that difficult. But it's even easier to ask Doug Plumb to
add an
Export feature. :->)

Send that guy a link to all these discussions, maybe he'll get
motivated and put some new features in...? Smile))

Brian
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Ethan Winer
science forum beginner


Joined: 08 Jun 2005
Posts: 37

PostPosted: Thu Mar 24, 2005 10:04 pm    Post subject: Re: Reverb room versus ETF Reply with quote

Brian,

Quote:
Send that guy a link to all these discussions, maybe he'll get motivated
and put some new features in...? Smile))


Doug Plumb keeps hinting to me that he's working on something new, but it's
been a few months now with no further news. And it's not like I don't have
plenty of other things to do! :->)

--Ethan
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The Ghost
science forum Guru Wannabe


Joined: 24 Mar 2005
Posts: 115

PostPosted: Thu Mar 24, 2005 10:04 pm    Post subject: Re: Removing hum from a recording Reply with quote

lemo5@optonline.net wrote in
news:1107751084.074551.60880@z14g2000cwz.googlegroups.com:

Quote:
After giving it some thought, depending on how the intensity varies,
the affects may be more far reaching, and since the file is longer than
one second you will have to deal with fractional frequencies as well,
so I think ghosts advise, to do an FFT, is good, it's to bad he's
dead.


This ghost thinks that you need to shake the dust off that book on your
shelf called a dictionary.


ghost, noun: The spirit of a dead person, especially one believed to appear
in bodily likeness to living persons or to haunt former habitats. The
center of spiritual life; the soul. A demon or spirit.
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Guest






PostPosted: Thu Mar 24, 2005 10:04 pm    Post subject: Re: Removing hum from a recording Reply with quote

I may not be familiar with them there fancy dictionary, but I make a
hard and honest living.
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The Ghost
science forum Guru Wannabe


Joined: 24 Mar 2005
Posts: 115

PostPosted: Thu Mar 24, 2005 10:04 pm    Post subject: Re: Removing hum from a recording Reply with quote

lemo5@optonline.net wrote in
news:1107893675.743862.11350@z14g2000cwz.googlegroups.com:

Quote:
I may not be familiar with them there fancy dictionary, but I make a
hard and honest living.


That's nice, but I fail to see what that has to do with either removing hum
from a recording, or with your incorrect assertion that this ghost is dead.

You wouldn't by chance be an alter ego to Bevis & Butthead of the audio
groups?
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Guest






PostPosted: Thu Mar 24, 2005 10:04 pm    Post subject: Re: Removing hum from a recording Reply with quote

Quote:
That's nice, but I fail to see what that has to do with either
removing hum
from a recording, or with your incorrect assertion that this ghost >is
dead.


Quote:
You wouldn't by chance be an alter ego to Bevis & Butthead of >the
audio
groups?

I have never been haunted before - especially over the internet, it is
quite an interesting experience.
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Brian Ravnaas
science forum beginner


Joined: 24 Mar 2005
Posts: 23

PostPosted: Thu Mar 24, 2005 10:04 pm    Post subject: Re: Reverb room versus ETF Reply with quote

i realize here that my 3dB FFT concept has some significant flaws. The
frequency response of the mic, the speaker, and whatever reflection
effects were occuring at that measuring position would have to be
accounted for, so...

if one wanted to attempt to scrutinize a single room mode and the
effect of some absorbing material on it, perhaps my idea was poor.

left with decay rates, which isn't so un-satisfying from a pondering
perspective.

in any case, i wouldn't hazard to describe me as an acoustics expert Smile
, i have some background in modal analysis in mechanical structures,
and i do find the analogy of in-room absorption tests to that
interesting.

Ethan, your thought about the graphical overlay is pretty ambitious,
but ineteresting. i wouldn't have a clue how to attempt that.

Ethan Winer said this:

"Then there's still the problem of some peaks being hidden behind
others. I
have a series of plots I took in the same room at five different
locations,
all with the room empty. In some room locations, modes that had been
hidden
behind others elsewhere in the room now show clearly, and vice versa"

Yes, that makes great sense. A common means of taking a peek at
mechanical modes is with a clamped free beam, like this:
http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html

Except in some potential extreme circumstance, the modes are very well
spaced in the frequency domain, and a single accelerometer position can
reveal the lot of 'em.

But at other times, one does impact or steady-state stimulation of more
complex structures, and this overlap can/will happen then, especially
in situations where damping is very high, and the modes are very broad.
In those situations it can be useful to find some location on the
structure in question where some given mode is maxmially expressed.
Sort of like finding the place in the room where some peak is maximum,
(i think). And then try again for another mode in the band you want to
look at, and so forth. Maybe you room acoustics folks have
models/sketches so sort of predict where these minima and maxima will
occur.

it can get tedious, but it's a necessary part of so many projects in
industry, and it's done all the time. The nice thing about your
project, i think, Ethan, is that you seek understanding of how those
things compare, and not (per your comments in the past) a formal sabin
number. Simplifies things alot.

that's part of the beauty of a reverb room and measuring the average
decay of many modes. This topic got me thinking about the possibility
of measuring a "diffuse" modal field in a mechanical panel. what a
pipedream that is, i'm sure the panel would be larger than most labs.
lol

perhaps it would be interesting to get a copy of ETF, i've never worked
with it.

Brian
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Angelo Campanella
science forum Guru Wannabe


Joined: 08 May 2005
Posts: 226

PostPosted: Thu Mar 24, 2005 10:04 pm    Post subject: Re: wall of water an effective sound barrier? Reply with quote

Brian Ravnaas wrote:
Quote:
Dan Jacobson wrote:
Just curious if water would be as effective as brick or concrete for
stopping sounds. Heavy and limp. Perhaps a wall of square water
jugs with no gaps.
the mass could be good if it was thick, and the traditional resonance
effects wouldn't be applicable.

That's my take on it. Some minor resonance effects from the stiffnesses
of the supporting wall (wood, steel, glass) will apply. But I expect it
to mainly follow the mass law.

Angelo Campanella
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Guest






PostPosted: Thu Mar 24, 2005 10:04 pm    Post subject: Re: Acoustics simulation by the BEM Reply with quote

You might also try

http://www.ScienceOxygen.com/math490.html ( Partial Differential Eqn )
http://www.ScienceOxygen.com/simulator.html
for some other applications...
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DM
science forum beginner


Joined: 24 Mar 2005
Posts: 2

PostPosted: Thu Mar 24, 2005 10:04 pm    Post subject: Re: Standing waves terminology revisited Reply with quote

A quick look at group velocity and phase velocity will reveal the source of
the word "Standing wave"
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The Ghost
science forum Guru Wannabe


Joined: 24 Mar 2005
Posts: 115

PostPosted: Thu Mar 24, 2005 10:04 pm    Post subject: Re: Doppler Distortion & the "Anonymous Non-believer" Reply with quote

Bob Cain <arcane@arcanemethods.com> wrote in
news:cti7sg130kk@enews4.newsguy.com:

Quote:


The Ghost wrote:

You claim that you have predictive equations. Based on your record,
I would suggest that you don't have squat. Post "your" COMPLETE
analysis and "your" closed-form predictive equations and prove me
wrong.

I did. You've seen it. I'm not going to do your research
for you.

Refute it if you can. If not, shut the f**k up. Nothing
you could have to say other than a reasonable refutation is
of further interest to me.


Bob


You did nothing meaningful, so there is nothing to refute. As per the
copy/paste of the post below, I am not alone in making that assessment.







Newsgroups: sci.physics, rec.audio.pro, rec.audio.tech
From: Jon Yaeger <jon...@bellsouth.net> - Find messages by this author
Date: Thu, 07 Oct 2004 20:55:22 -0400
Local: Thurs, Oct 7 2004 5:55 pm
Subject: Re: Basic Acoustic Derivation/Proof Needed
Reply to Author | Forward | Print | Individual Message | Show original |
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in article Xns957BB5D488546theghosthotmail...@64.164.98.6, The Ghost at
thegh...@sbcglobal.net wrote on 10/7/04 8:49 PM:




- Hide quoted text -
- Show quoted text -

Quote:
w...@needs.email.anyhow (Goofball_star_dot_etal) wrote in
news:41657179.63226838@usenet.plus.net:

Well, I am not particularly keen to trash his work in public, behind
his back but aren't you just a teeny weeny bit concerned that to reach
the conclusuion that he does, that he really needs to know the
position of the speaker cone in relation to the frequency/phase
modulation? And you a self-proclaimed scientist and all.


Quote:
Bob Cain can call himself whatever he wants. However, not only is he not
a
scientist, he is not even a c-grade engineer, which is evident from the
fact that he is so technically inept that he had to come to sci.physics
begging someone to spoon feed him through the trivial solution of an
elementary one-dimensional wave equation which is discussed in virtually
every introductory textbook on acoustics. Worse yet, he is still making
up
and using meaningless terminology and pulling clearly incorrect equations
out of thin air, so he still doesn't understand the solution that he was
spoon fed.



And that's the charitable explanation! Wink
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Bob Cain
science forum Guru


Joined: 07 Jun 2005
Posts: 360

PostPosted: Thu Mar 24, 2005 10:04 pm    Post subject: Re: Doppler Distortion & the "Anonymous Non-believer" Reply with quote

The Ghost wrote:

Quote:

You did nothing meaningful, so there is nothing to refute. As per the
copy/paste of the post below, I am not alone in making that assessment.

Refute the equation I derived or admit you can't.


Bob
--

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

A. Einstein
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