Build a laser listening device for less than a fast food meal.
Video after the jump.
“In a microphone, sound waves (differences in the pressure of air) cause a diaphragm to vibrate back and forth, altering its resistance to an electric current. When an electric current passes through said diaphragm, the output forms a complex signal which can then be reinterpeted by speakers or a recording device as sound. The device shown here works in a very similar way. Sound bounces off of a window, causing minuscule vibrations (acting like the microphone’s diaphragm). When a laser is trained on the window, its reflection will vibrate with the sound. The laser’s reflection, if converted to an electrical signal can now be recorded as sound. I will outline how I made my own (cost me $3, hope yours is the same or less) - the technically savy among you will spot the countless variations possible on this basic idea.”
August 16th, 2007
That’s pretty slick! It’s too bad you have to not only setup a laser to hit the window, but also find the reflected light. That makes it near impossible to actually listen to conversations “hundreds of yards away”.
You’d basically have to be perfectly perpendicularly positioned (or close enough) to even find the reflected light beam (& that’s assuming you have a bright enough laser to reflect off of a transparent window).
Still, ultra cool that this can be done at all! You just have to hope for some really thick curtains so the people behind said window don’t see a red dot on their far wall.
Hm… Is there a way to filter the light from an invisible laser so you could see it through a camera or something (infrared? UV?). Then you could set it up by looking through the camera, but the people on the other end wouldn’t see any signs of a laser listening device… Hm…
August 16th, 2007
I’m surprised at how well this works. I wonder how much, if any, improvement there would be by sticking a mirror on the window. At least that way it would be a little more discreet too.
August 16th, 2007
thats stupid
August 16th, 2007
Omg saw those stickmans? I was laughing hours.
August 17th, 2007
JOEBOB GO F*** YOURSELF
THIS IS REALLY GREAT!!!!!!!!
August 20th, 2007
copied from one the spymaters episodes from discovery channel.
Nice report but forgot one thing. the KGB put a smalll prism in the window glass of the american embassy to make things simple. thats why all new emabssies and CIA offices have two layers of glass facade.and one more thing this thing will work only with an amp.URBAN MATERIALS
try theremin bugs.They are kickass.
and lasers or any light source can be reflected off a transparent window if u go above the rafraction angle.
an infrared laser from a cdrom.A IR sensor.ONe amp. Lots of calibration.One very noisey spyphone.
August 20th, 2007
You could use one of those $1/$2 “spy ear” kids listening devices as the amplifier, just swap the microphone for a light dependent resistor.
And use a low power IR laser diode placed in a laser pointer housing for an invisible beam, you would need a digital camera to see the laser dot for alignment.
October 16th, 2007
more detail?
October 16th, 2007
Hi Hossein,
There is a link in the article that provides more information.
May 4th, 2008
Wonder if a parabolic mirrored dish (like from a flashlight) would help catch the reflected beam better. You’d have to mount the photocell backwards though. Similar to a parabolic mic or sat. dish…
May 24th, 2008
can we using this for lan network on UTP cable for p2p configuration?