test for independence of audio signals

Hi there everyone. I am currently doing a project on blind source separation of audio signals and one of the requirements is that the signals are independent of one another. does anyone know any built command of matlab or way to test for independence of let's say between 2 audio signals.

[Jan]

I'm not sure, how independence is defined. Perhaps CORRCOEF(Sound1, Sound2) is enough already?

[ckchew]

thanx so much for the help Simon!:)