No DIY espionage kit is complete without a long-distance listening device, and no DIY long distance listening device is complete unless it uses a sweet laser in some form or fashion.
If you agree with that statement, then you're in luck, because the following project will show how you can use a laser pointer to hear noises from hundreds of feet away.
material :
Laser pointer, Old pair of headphones, Cadmium Sulfide Photocell (available at most Radio Shacks or electronics store), Tripod, Binder clips or duct tape, Laptop or other recording device.
Clip the earphones off your old headphones, and strip back the protective conduit to expose three wires (red, white, and black).
There are two contacts on the photocell. Solder both the red and white wires to one contact, and the black wire to the other.
Plug the headphone jack into your laptop or other recording device. Using binder clips or duct tape, secure the
photocell to something sturdy so that it can be easily moved and aligned.
Again using your clips or tape, attach the laser to your tripod and secure the power button so the laser remains on.
Find a room with a window you'd like to spy on, and aim the laser at the window at an angle. Determine where the laser reflects, and situate your photocell so the reflected beam hits the front of the cell.
Any noise from inside the room will cause the window to vibrate, which will get picked up by the laser and
photocell. You might have to process the raw input to remove unwanted noise and isolate the voices. Check out the cool video to see it in action.