Lighttosoundconverter
From the MAKE: Flickr pool

5Volt shares info, schematic and video on this simple yet fun/interesting project –

This is my simple light to sound converter. It simply converts light variations into sound. Listen to remote controls, TVs, burning flames, light bulbs and anything that emits either visible or infrared light.

Get more details on how to build your own from his blog – Light to sound converter