h a l f b a k e r yTrying to contain nuts.
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As I currently work at night, when I arrive home at 7 in the morning to go to bed, the rest of the world is startng to wake up. I tried for the longest, to think of a way to destroy all the birds in my neighborhood, but instead I thought of a less violent way to solve my problem. Sound Proof windows.
Pretty simple, they would work on the same principle as sound proof headphones. A double paned window with six sound sensor/recorders on the outside. One in each corner and two on either side of the middle. The windows will have a hallow inside, like many windows today, except it would have six small speakers corresponding to each sensor on the outside. And maybe a slightly thicker than normal inside pane. The unacceptable noise from outside would be recorded and as it passed through the windows first pane. An exactly opposite wave would be played (the same wave just some fraction of a second later) as it passed through the middle pane, therby cancelling out the original waves, and hopefully, not allowing for any sound to enter my bedroom. If this works the implications are pretty cool. Imagine a completely silent house (if you wanted). No loud motorcycles, no loud speakers, nothing to disrupt you.
1987 Time Magazine Article: "The Art of High-Tech Snooping"
http://www.bugsweep...itech_snooping.html
Laser bounce window eavesdropping detailed along with other techniques. [bristolz, Jul 07 2005]
Window Speaker
http://www.m-media....ays/s3i/omnivox.php
[Worldgineer, Jul 07 2005]
Google Answers response to soundproofing problems.
http://answers.goog...hreadview?id=507807
[DrBob, Jul 11 2005]
[link]
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This could work; would it be better than triple glazing? |
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Gets my muffin. Except I think that should be "noise cancelling" rather than "soundproof." |
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Neat idea. Would you need all six
sensors? I would have thought (just
guessing) that the outer pane of glass
would reverberate mainly in a 'simple'
mode, with the centre oscillating most.
With luck, a single sensor/cancellor pair
in the middle of the inner and the outer
glasses might be enough.
I don't
know how good triple-glazing is, but
any system only has to be as good as
walls and window-frames around it. No
point blocking 99% of window-sound if
wall, vents, frames and whatever
transmit 3%. |
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This sort of thing can work only for very small areas such as the cavity inside a headphone. For large areas—like a bedroom—there will be areas of constructive and destructive interference, eventually averaging out some distance from the window, where the net effect will probably be more noise than before. |
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Where would the interference come from? The sound would be cancelled within a relatively small area, the center of the window. If much of the sound never makes it through the windows, what will, whats left of the waves, have to interfere with, besides the small amount that comes in elsewhere? And how could these dilluted waves create more sound than the original? |
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[ldischler] and [2021] - I'd be optimistic
about this working. [ldisch']'s point
applies to a case where you're trying to
cancel out noise which is already
bouncing around within a large volume.
In this instance, you're trying to block
sound on its way through a relatively
well-defined system (the
window).
I would imagine
that, in response to noise, the outer
pane of stiff glass will vibrate in a
simple mode, with the centre-point of
the pane more or less tracking the
sound waves. The inner pane will
behave similarly, though at a lower
amplitude.
Thus, the inner
pane is effectively behaving like a
simple loud-speaker cone (crudely). An
antiphase generator in the middle of
this inner pane (and driven by a suitably
attenuated and antiphased signal
picked up directly from the outer pane)
would probably cancel most of the
vibration in the inner pane. I bet this
would work to a fair degree. |
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[KaGe] - as I understand it, the
interference is picked up from the outer
pane. This would be the best source,
since its behaviour should mimic that of
the inner pane (same size, same shape,
same material). |
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//Where would the interference come from?//
Interference is a property of waves. You have one source (the outside frame, which is vibrating in a complex way) and you have six more sources—your speakers. For complete cancellation, all of the sources would have to be coincident, but since they aren’t, you’ll have regions of destructive interference, where there is less noise, and regions of constructive interference, where there is more noise. If you have 40db coming through the window from outside, and you produce 40db of out-of-phase noise with your speakers, you will get an average of 43 db at some distance away, ie, twice as much noise. |
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I suggest you all test drive the Acura RL if you get a chance. Fairly large cabin space, certainly much larger than headphone cavities, and amazingly effective electronic environmental noise cancellation. A cottony silence that must be experienced to be believed. |
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Unless I'm missing the point here, I
think we're dealing with a very different
situation from a standard ambient-
noise-canceller.
We are not
talking about picking up noise 'in the
air' and trying to cancel out 'in the air'
(which is indeed diffcult).
Instead, we are talking about
trying to stop the glass panes vibrating
(ie, transmitting sound). Since the
outer pane can be used as a 'pickup'
with very similar properties to the inner
pane (which is then driven in
antiphase), I would expect this to work
quite well. |
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Actually, you may be able to cancel noise effectively by attaching a white-noise driven dither generator to the inside pane that just drowns out the outside pane vibrations. |
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As for bris's automotive example, I’ve seen a patent where microphones are placed above the passenger seats, and the canceling noise is generated to minimize the noise at those locations. |
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ldischler
Ok but when the vibrations hit the outer window they will be reverberated within the window as one sound. The window should emit one wave compromised of all the sounds. So, as I said earlier there is not really a need for six speakers. Two options present themselves. One take all six recordings, merge them, and play them into the window as one sound with one speaker. Which should be pretty close to what the window pane is producing. OR Record the sound directly from the window pane somehow? Im sure it could be done. The glass will be vibrating with sound. Somehow extract the waves from the vibration and this way you could more accurately produce the exact sound.
If I am somehow missing/overlooking some fundamental part of the physics please teach me where im wrong. I dont pretend to know more than I do. |
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In the case of the Acura, the car owner told me that there are 2 transducers in the ceiling from which the the cancellation signals are processed. (Lexus had earlier used many transducers in the chassis but never really made the option available). |
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As for gleaning sound from the glass pane, lore has it that the Soviets did that with lasers bounced off of the Pentagon's windows, recording conversations from within the offices. Upon discovery of the eavesdropping, the Pentagon installed loudspeakers around some windows that continuously play white noise to drown out the conversation. The article I link to seems to raise the possibility that this is possible but not that it has been done for certain. |
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The laser-off-the-window trick is one
thing. But it is even easier to pick
sound off a window (or any surface) if
you can attach a transducer. Effectively,
the outer pane of glass is simply the
diaphragm of a microphone. This
should work. My only doubt is whether
it would be more effective than triple-
glazing (which can virtually eliminate
transmission of sound through the
glazed area). |
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//reverberated within the window as one sound//
No, there will be a complex mix of frequencies, each of which will act as if it's independent of the others, and the amplitude and phase of the frequencies will vary across the pane in a complex way. So, it's quite a mess. With cars, the approach is to dampen the predictable noises, say engine nose, which has known frequency components, but even there, sudden changes, such as when you rev up the engine, can throw it off. |
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I sleep on a totally different schedule than my house-mates. They always wake me up >:l
A full night of interupted sleep would be great... |
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//A full night of interupted sleep would
be great..// No it wouldn't. |
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[thesmog] my old housemate had the ultimate solution. He was stone deaf. |
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He had a cochlear implant, which allowed him to hear in the day, and he shut off his bionic ear at night. |
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It was nice to be able to crank the music when he had to be up for work in 3 hours. |
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I don't go to bed till atleast 3am, most nights.
I get up, and go back to sleep after 8am. I want this, I need this, and dern it, if it were possible, I would purchase a handfull. |
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Excellent first idea, Ka. |
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[id]'s first anno was on the button: the noise cancellation is really only effective exactly at the location of the sensor, then as the area increases you get destructive/constructive zones where the noise will be either much quieter (good) or much louder (very bad). It's a bit like feeling the heavy thrum of your engine's idle note wafting in and out with a big truck next to you at a stop light, only the effect in this case manifests spatially instead of temporally. |
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Thick windows are better. Triple pane with a storm outside. Maybe add a storm inside. That way, when the power goes out, your noise cancellation still works when the big noisy power trucks come in the middle of the night. |
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If you want a completely silent house, try strawbale construction, with extra-thick stucco in and out. It's like living in a tomb. |
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Reverberation could make up a large part of the sound level - make sure you have fewer reflecting surfaces (including the inside of the glass window). |
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I'm not sure I'm right but wat I think is happening is that the sound is really air particals moving.
which in turn make the glass particals move , wich make the air particals on the other side of the window move.
If you would have double glazing with a easy compressable gas in between, than the gas would dampen or absorb the sound. |
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//If you would have double glazing with
a easy compressable gas in between//
as opposed to that damnably
incompressible air, then? |
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Here's a thought: fill the space between the panes not with a gas but a vacuum. |
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Granted, for a window of any useful area the glass is going to be very thick. Probably thick enough to stop any intruding noise, even. But this is a silly idea so we're going to annotate in that spirit. |
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The inner and outer panes will both be of this herculean dimension, each easily thick enough to attenuate any noise, but with a vacuum between them noise transmission via the panes will be nil (all bets are off for the frame), and the window should perform better thermally, too. Where's the bad side of this? |
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Oh, right: it weighs four hundred pounds. |
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What you really need for noise cancelling is a huge, flexible house (perhaps a gigantic bouncy castle) with a built in generator that wobbles the entire structure at some scientifically chosen frequency. |
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Imagine a whole street of the things wobbling around. It would make you feel seasick just driving down the street so it would probably be effective at reducing the local traffic volume even if the acoustic properties didn't have much effect in themselves. |
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YOu might be able to do it with some
kind of fog (instead of gas) in the gap. I
half-remember reading somewhere that
fogs can attenuate sound under the
right circumstances because the
pressure-waves of the sound cause
increased condensation/re-evaporation,
thereby absorbing the pressure
difference (and hence the sound). Of
course, you may not want windows full
of fog. |
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What if the BATF shows up to investigate my marijuana grow operation and demands that I come out with my hands up? This could be dangerous. |
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Program the noise canceller to become an infrasonic noise generator, and while everybody's clutching his insides trying to figure why their bellies are churning at 12Hz, you grab your stash and run. |
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I'm bunning it because I want to see a prototype. |
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Triple-glazing is more effective insulating sound and temperature. Low tech solution and instead of using energy this saves energy.
I am not adding this to my Eco-House |
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