Howdy, Due to weight limitations, I could only use so much mass in my design. I feel that lack of mass is the weakest link in my plan here. But, it was either do what I could, or not have a studio room. Room is about 600 sq/ft overall, 11 ft average height ceiling (slanted ceiling). Room within room construction. Outer walls... 2X4 studs filled with 3.5" R-15 fiberglass batt insulation, then one layer of 3/4" plywood screwed to studs, one layer of 1/2" homasote (pressed paper "sound board") screwed down, and one layer of 1/2" sheetrock, screwed down. Then, the inner room frame is to be build with 2X4 studs, filled with 3.5" R-15 fiberglass batt insulation, and then just ONE layer of 5/8" sheetrock only! (I wish I could put more layers on this inner room wall, but I cannot add more weight than this.... everything is on the second story of a wood framed building). The one sheetrock layer of the inner wall will be spaced about 10 inches away from the outer wall all around. Inner room will be "floating", sitting on some strips of Sheetblok. Floor will be decked and floating on some U-boats. Floor will be decoupled from inner room walls. (Overall, the floor and ceiling have the same integrity as the walls described here.) This room is to be used to track drums. The goal is to keep the sound of the drums from reaching the outside of the building and disturbing the nearby neighbors in this very quiet neighborhood. I am already accepting that there WILL be some sound leakage to the outside, but I guess the concern is how much? Does anyone care to predict what the overall STC of this set-up might be, and predict how much drum sound will leak to the outside? I am hoping it will just be a "faint" sound of drums leaking to the outside, to the point where people inside neighboring houses (houses are about 30 feet away) will just barely hear it or better yet NOT hear it. But, I fear that I may wind up with a situation where the drums are still pretty darned loud outside. Wish I could know prior to completing this project. So far my outer room is essentially done, now about to start on the framing of the inner room. I am guessing that I will need to "deaden" the inside of the inner room once done to reduce resonances. I have always dreamed about having a nice "live" room to record in, but according to some things I have read, there will be less sound leakage to the outside if the inside of the room is "dead", as opposed to "live". I think I will need all the help I can get to keep the drums from leaking outside. For those of you who aren't familiar with acoustic drums, they are LOUD.... very high SPLs... like shotgun blasts. Sure wish I could have added more mass, but... this is the only room I have to work with, it's either this, or nothing. Any tips, comments, ideas etc appreciated. Thanks!