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Eric's new LITE2SOUND kit sounds like a lot of fun. He reports on some early experimentation using the board's photodiode sensor -
pointing it at a computer CRT yields a strange humming tone that varies depending on what the screen is displaying. The LED in an optical computer mouse plays strange chirping whistles. Infrared remote controls make wild bursts of noisy data. You're hearing frequencies from lines of code executing in a microprocessor... stuff that was never intended to be heard. When you combine LITE2SOUND with a laser pointer, things get really interesting. There is bizarre audio from a vinyl record as it spins on the turntable, using a laser instead of the needle. Listening to reflected laser light as you move it over the surface texture of objects is often a surprise; it plays the texture like a phonograph needle. You can even pick up unusual sounds from a guitar string as the laser reflects off of it. There are still many things to try...Further explanation, ordering info and a bunch of interesting sound samples can be found over on ericarcher.net.
You could also try hooking up a CdS cell, photodiode, or small solar cell to an audio jack and plug it into a microphone input. An instrument tuner that displays Hz can be used as an optical tachometer.
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Really cool product!
The germanium diode in a crystal circuit can also interact with light and produce some interesting results.
I have been experimenting with the simple crystal circuit inside a meditation aid "Beta Blocker Radio" from EJ Gold. Normally this particular radio does it's magic passively, but I hacked into it and ran an audio line-out to my iMac computer. I use Audio Hijack Pro as a real-time DSP and recording tool, and then the fun begins!
The diode in this crystal radio circuit reacts quite differently to laser, white DC light, AC light, and even candlelight. I have a movie of this effect at http://www.youtube.com/watch?v=v10_By6J_CM
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