Searching Sound
Technology Review has one of their few stories that's not registration-required describing searching audio files for any specified set of sounds. All sorts of interesting applications become possible if you can turn analog audio into a digitally-useful product without massive human intervention.
If you really want to find out how it works:
;)
Links to PS and PDF files are on this page
http://www.cs.waikato.ac.nz/~nzdl/publications/
(They are not going to like what I am about to do to their server