Have you ever needed to hear a conversation in a room you are unable to access or bug easily? If so, and if that room has a window, you can using a laser microphone.
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
The things you need for this build are very easily obtained and cost me about $10.
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
If you bought headphones, use the scissors to cut the actual headphone part off. We'll only need the cord for this so you can save the speakers for another project
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
Using the tripod or other way to keep it steady, point the laser pointer at a window so that the reflection is in a spot that is not too difficult to reach. Now just position the photocell so that it's in the reflection. after doing that, connect the cord to the microphone plug-in and if you're using a computer, open your recording software. begin recording and it should pick up the sound.
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.
Step 4: Thanks
Thanks for reading through my first instructable. If you liked it, please vote for it in the spy contest. Please don't try to use(or at least don't get caught using) this for anything illegal.