[racket] Audio input

> A couple of my students are toying with the idea of generating pseudorandom numbers from ambient sources, and want to try using audio as a source.

Perhaps John Clements' Portaudio bindings would be a
platform-independent way to get sound from the microphone.

http://planet.racket-lang.org/package-source/clements/portaudio.plt/2/3/planet-docs/portaudio/index.html

Hmmm... but the documentation doesn't say how to use the bindings to
access the microphone though.  Does anyone else know how to get at the
mic via portaudio?