Distinguishing Noise from Sounds - a question of recognition?

Hi there,

Does anyone know of anyone researching into the identification of different noises, as opposed to distinct sounds, and can they point me at them please?

By "Noise" i mean multiple asynchronous multi-source sounds which equate to radio "Squelch", and by "Sounds" I mean single source audio output which can be identified (with practice).

We are working on identifying large flocks of birds who all tweet and flap asynchronously at www.withymbe.info

Many thanks,