My band uses a garage for rehearsals (cant afford a studio). Got many complaints from the neighbors, police showing up, dogs howling, etc... The keyboard plyr (who owns the house/garage) decided to completely sound-proof the garage. we did a bit of brainstorming and came up with a master plan; we would fabricate a stand-alone sealed structure WITHIN the garage!! We built a large room inside the garage which sits on 4 big rubber pads. theres about 20" of free space surrounding the room to provide access to the interior walls of the garage in case it was needed. Took a coupla weeks to build and has a nice ventilation system ( a/c with inlet & vent). It is 100% effective. The band can be playing full tilt in the room, and a person standing directly outside the garage hears only the subdued thumping of the kick drum. At 60 feet, (the neighbors yard), you hear nothing 'cept the birds and crickets! All said and done, the project cost a little over $2k. But we figure we would have spent close to that for a year's worth of rehearsal studio time. Id like to hear from any of you who have tackled a similar problem.