I was involved in planning a recording studio once (never got around to building it, as the chief engineer divorced the producer's daughter and wasn't welcome there any more but that's a whole nother story!). If you are worried about noise from outside the studio leaking in, the best soundproofing is multiple layers of sheetrock, separated by lath running horizontally -- spaced about 18" or so. The more layers, the better the sound-insulating quality. This is the method used at GOOD hotels (such as I've only ever slept in once!), and in one local tv studio here in coffeetown that butts up against the freeway (expressway).

Studioless in Seattle,
Alex
O..O
=o=