A laser microphone is a device that uses the vibrations of a window or similar pane of glass or plastic to record sounds near said window. A laser is pointed at a window and a photocell is placed where the laser's reflection lands. That photocell is then connected to a recording device. The vibrations of the eindow causes slight movements in the laser's reflection which, in turn, cause small fluxuations in the photocell microphone's current. This may seem complicated but it can be done cheaply and easily.
Step 1: Things Needed
Soldering gun( or just electrical tape if you're being really cheap)
Scissors( if you're using headphones)
A laser pointer $1.50
A photocell $.30
A bad pair of headphones or, as I used, a speaker cable ending normal headphone jack $3.80
A tripod $0.00( already had one and isn't needed)
Recording device or computer with recording software
Step 2: Assembly
Connect the photocell to the headphone's cables. Solder it or just tape it with electric tape.
That's it, really. It's that easy.
Step 3: How to Use
If you want higher quality sound and less likelihood that people will see it, use a red laser to aim, then put an infrared laser( way too expensive for me and too hard to find) in it's place.
This project works best in dark places.
Curtains may help hide you but they muffle the sound quite a bit.
I had a sound file but there was a lot of light pollution in the room from an emergency light and the laser was being bounced off a clock's face which added a lot of background noise. I will upload a new sound file when i have a chance to make one.