i was asked to do sound design / processing for a live performance-art act. specifically, i need to be able to pick up live sounds from several locations across the stage, mix and process them simultaneously. one challenging scenario is this: the performer/dancer will be crawling on the surface of some sort of round metal container (about 4 meter diameter) full of gravel (about 1 meter deep). what i want to do is install a few microphones inside the gravel pool (say place them 20-30cm deep), in order to pick up and amplify the friction sound produced by the gravel as the performer will crawl on its surface. additionally, i'd like to be able to pick up and amplify the performer's breathings as he crawls.
question 1: what would be the best type of microphones to use in order to pick up the gravel sound?
question 2: what would be the best way to pick up the performer's breathings? - the solution must not involve attaching a mike to the performer's body.