Inspired by Quality of random numbers I would like to set up a true random data generator in Mathematica.

My idea is to use the static from an open microphone. I recall reading about extracting the "most random" data from such a source but I do not remember the specifics. Presumably all recognizable patterns and frequencies would need to be filtered out, and the remaining data "balanced" (for lack of a better term) to get a uniform distribution.

I would like to know how this may be accomplished and what quality and quantity of random data I could expect to to gather. If the mic static idea is not valid, I would like to know what other options exist.