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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.
The only thing I'd put in a gravel pit is an SM-57 or 58. Those things are crazy durable. anything less robust will be seriously damaged. Sound quality is kind of crap though.
My next thought is that you could rent 4 wireless mic kits and set them around the edge of the pool (or just two on opposite sides from each other). I'm assuming that the performer will have a particular way of doing the gravel sequence since it's part of a larger routine. In that case you can get down to one if they're really consistent in rehearsal.
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for gravels, i would opt for contact mics / piezo strips.
for breathings.. well, if you can't attach anything to the performer's body, you can only try with a shotgun mic placed on top of it (if he will stay in the same place for the whole performance).
It might be worth discussing a wireless with the performer otherwise you are going to have cables everywhere. If they are really anti-wireless then you could rent a parabolic dish and connect it to a wireless transmitter and follow the artist round with that.
When I have had to do unusual events like this I mic everything with Audio Technica cardioid lavalier mics in AT8418 Unimounts and have attached them successfully to all sorts of objects.
The unimount has a built in pop screen which also acts partially as a suspension mount, as the foam completely encases the mic isolating it from the support.