Laser microphone countermeasures

I've googled for laser microphone countermeasures and can't seem to find a specific reference to this in particular.

Would taping a material such as, for instance, aluminum foil (or other material, but aluminum foil or tin foil in particular) over windows, so that the foil would vibrate against the glass when interior sound waves were generated, make those sounds inaudible or more difficult to discern clearly in the case of an outside laser microphone or other similar device? Why or why not?

(Someone told me this and I wanted to know whether they were correct or not.) Thanks, and my apologies if this is an elementary or already covered question. (I did search! lol)

Edited for punctuation.

[edit on 6/26/2007 by AceWombat04]

If someone was serious enough to use lasers to eavesdrop on your conversations, a bit of foil is not going to stop them. For anyone who doesn't know, a laser microphone works by interferometrically detecting the minute vibrations in such things as windows caused by the alternating air pressure that our ears interpret as sound.
Air is devilishly tricky, and no matter how tightly you stick that piece of foil it probably wouldn't distort the microphone readings much at all. I don't know where the operator has to be positioned relative to the window - because you would think that they would have to be exactly 90° out from the flat surface for the laser to bounce back straight at them, but the practical implications of that would make it near impossible - so even taping foil on the outside of the window to distort the out-going laser would not work.
If you taped foil on the outside of the window, but not touching the window, and then cut a few slits in it, that would probably work. But if you couple that with walking about in a tinfoil hat (which no doubt you do ) then the neighbors might start getting the wrong impression. Or the right one . . . ?

Double planes of glass would work well, but that would be very expensive. Your best bet would simply be to cover up the glass so that your eye cannot see it, which means a laser cannot see it. And I would think that a pane of glass that is rigidly set into the frame would transmit sound much better than one which is 'rattly' and loosely set.
Forgive me for asking, but why on earth do you want to know about countermeasures for laser microphones?

Thanks for your prompt response and insights (and you made me laugh too, with the tinfoil hat comment lol.)

EDIT: I re-read your reply, and decided to add that the claimed purpose of the foil was not to deflect the laser, but rather to cause additional vibrations that would mute or distort the window's vibrations. Would that work?

RESUMING ORIGINAL POST: Well, in recent days I've been told some slightly differing accounts of things that transpired before I was born. It involves family, so I don't want to elaborate. Sufficed to say, I trust them, and would like to chalk up inconsistencies in their versions/stories to age, imprecise recall, etc. One of the things one of them told me was that tin foil or aluminum foil could be used to counter monitoring that was dependent on window vibrations. I want to believe that, but something just felt inherently incorrect, or at least incomplete. Your post would seem to suggest the same lol. I'm thinking both their memories just aren't what they used to be, or that they were simply misinformed.

[edit on 6/26/2007 by AceWombat04]

Originally posted by AceWombat04
I've googled for laser microphone countermeasures and can't seem to find a specific reference to this in particular.

Would taping a material such as, for instance, aluminum foil (or other material, but aluminum foil or tin foil in particular) over windows, so that the foil would vibrate against the glass when interior sound waves were generated, make those sounds inaudible or more difficult to discern clearly in the case of an outside laser microphone or other similar device? Why or why not?

(Someone told me this and I wanted to know whether they were correct or not.) Thanks, and my apologies if this is an elementary or already covered question. (I did search! lol)

Edited for punctuation.

[edit on 6/26/2007 by AceWombat04]

Laser eavesdropping is an outdated technology, heck back in my high school electronics class I had an option to build one and that was back in '88.
If you think someone is using such a device against you then you might just use something as simple as a back massager thats taped to the window, that will negate most vibrations that come from ambient noises such as voice within your house.

No, I don't suspect I'm being eavesdropped on lol. I was just told a story in the last few days that I am checking up on for plausibility. Specifically, it involved the use of tin foil/aluminum foil being taped to windows for this purpose, and I'm trying to figure out whether that makes sense or not.

I think the window itself can act as a relay of the wave.

This site sells the plans for such a device.
www.amazing1.com...

I would try a jamming device or noise cancelation device which would produce a oposite wave. I think foil would amplify the vibration.
[edit on 27-6-2007 by Freezer]

[edit on 27-6-2007 by Freezer]

I should clarify again that this isn't because I myself seek such countermeasures, or because I suspect I'm being spied on. Someone told me a story, and I'm testing the scientific plausibility of that story based on the expertise of those here at ATS, who I'm sure in most cases know far more than me about pretty much everything there is to know lol.

My understanding about how laser mics work is that when people speak, changes in air pressure caused by sound waves cause vibrations of a diaphragm, and those vibrations (in a standard microphone) would be translated into electrical information, whereas with a laser mic, the laser detects movements of the window pane in response to interior sound waves, with the window pane essentially acting as the diaphragm and the laser allowing the changes to be translated into electrical information that can be recorded as sound.

What was described to me was a process whereby simply taping aluminum foil (I don't know if they meant tightly of loosely) to the inside of a window would cause those vibrations to be artificially muted or altered, because the foil itself would vibrate against the glass. The person who told me this said this would make any discussions recorded, while still audible, largely unintelligible.

Specifically, is there any foundation for this?