TIL - Laser Microphone

[hoochymamma]

Honestly, I had no idea such device exists.

It turns out there are expensive as **** devices used by intelligence agencies (but can also be bought from some selected companies) that can eavedrop windows for up to 400 meters away.

Imagine to possibilities with such device, you can literally eavedrop every single person you ever dream of without zero to no risk.

[mjj9994]

That is like 1980s technology. Today the agencies could probably just tap into your cell phone/smart tv/alexa and listen through that.

[sndprv]

[reggind]

The results are really not super. Some researchers at MIT got interesting results from some videos that were captured at a high speed by detecting micro movements in inanimate things. The laser based systems reflect off of a window and generally at a long distance. So you have both the fact that your microphones diaphragm is a piece of rigidly held glass, so there is not a lot of displacement, combined with the fact that they also work just as well the other way, that is outside noises can excite them as much as inside noises, and air effects on the laser beam itself. One of those things where I would say it can not be done, but the results are probably not what you are hoping for. The MIT people got much better results, I think the has demos using a leaf on a plant, and the best result was a potato chip bag. Oddly that makes sense though as most microphone diaphragms, at least for dynamic and condenser mics are generally some kind of thin mylar. Ribbons being the odd men out but they are so low output they would not be near my top choice for this hobby.