Have you ever seen those music-synchronized lights before? They're pretty neat. This intructable will show you how to make a device that sends your voice or any other form of audio over a beam of light. The picture below is the finished product. I found the information on this project here. Please note that I used a lot of salvaged parts for this project; you could ultimately make a much better version with the right parts. I have tried to use this setup with a laser, but they seem to be too sensitive, and burn out easily. If there is a very simple solution to using a laser with this, please let me know. There are videos of it in action below.
-A CdS Photocell
-Some battery holders with battery clips if needed (one for the audio-to-light modulator [transmitter], one for the receiver, and one for a microphone (optional))
-An Audio Output Transformer (RadioShack Catalog No. 273-1380)
-Some form of amplifier (I used a battery-powered one from RadioShack (Cat. No. 277-1008))
-Some MONO (NOT stereo) audio jacks (Three will do)
-Some form of LED, Preferably a bright one
-A container to hold all the doo-dads in (for the transmitter). I just used what I had: a pill container. You want to keep all the circuitry concealed in some form of container, because if you touch the circuitry, I found out it gives you a small unpleasant shock (because of the transformer?), and it disrupts the signal to the LED, therefore giving you a bad signal.
-Some hook-up wire
The Pictures below are what I had to buy (except for the mics). I salvaged the rest.