[Acen]

Something that's always amazed me doing live sound work, is how sensitive mics are to what I'd class as practically inaudible noises.

Say I have a mic on a stand at the back of a room (i.e. Earthworks M30), someone can enter the door from the opposite side, and quietly walk somewhere else in the room. The mic will pick up each step they're making in a pretty obvious fashion on a spectrograph in Smaart. Or a fan from an LED light hanging from truss in the ceiling.