getActivity for incomming netStream

I have an app which makes a little clip dance when the microphone activity goes high enough. That's easy, just check Microphne.get().activityLevel

I also, however, have an incomming netStream which I'd like to do the same thing with, make the little clip dance when the activity on the incomming stream goes above a given level. This isn't so easy, there is no activityLevel properly on a netStream it seems.

Anyone have any clue how I might go about finding such a thing?

Thanks.