Ceiling Pocket - Fire Code vs Soundproofing

I operate the Amherst Red Barn Music School in Amherst, Mass and I am building a soundproof classroom/rehearsal/recording room in the basement of the historic Dickinson grain building. Fifteen years ago, the architect/owner jacked it up and put in a double drained basement. Overhead, we have log joists with the bark still on, just to give you an idea, picture follows. And on top of that, a wooden office building separated by a six-inch steel-reinforced poured concrete slab. Under the logs, I constructed a joist system that projects up between the joists in order to create a 9 in. (23 mm) pocket, stuffed with fiber glass. I did this at the suggestion of the sprinkler engineer, because of gas and water pipes in the hall that we didn't want to move -- it's a can of worms. He said it meets the prescriptive code. See NFPA Code Rev. 2007 P. 13-66 - Sprinkler Installation, Section 8.8.7,Ceiling Pockets, P. 13-66, attached below. Fingers crossed. In this case, I do not have a sealed, double joist system; and the 52 in. joists are attached to the beams. The ceiling itself will be two layers of 5/8 sheetrock with a layer of elastomeric caulk in between. To RC or not to RC, that is the question. Thanks for your help. Cheers, Kevin