Not to heap on the bad news, but here's my experience:
Had a basement studio. it was on the earth side of what's called a "day basement" (aka "walkout basement'). When a band was cranked up, you couldn't hear yourself think inside the house. Outside, a 100 feet away, it was bearable, but mostly due to the kind nature of my neighbors, i was able to continue. Big sessions I would send family to the movies or something (much cheaper than soundproofing!).
Baby was born. Nursery was directly under neath studio. Commence initial attempts at sound proofing. Put up resilient channels, flexibly metal strips that affix to existing walls, allowing a second inner wall to be installed. The inner wall can presumably flex a bit on the resilient channels, to attenuate some sound. The 1" gap between inner and outer wall is supposed to also provide relief.
Replaced hollow panel doors with industrial grade oak doors with tight sealing metal frames (heavy cast steel). Neoprened all the seals of doors. Put insulation in ceiling joists. Put two thicknesses of sheetrock on resilient channels for walls/ceiling. Caulked gallons of goop into every conceivable joint/crack/microscopic pore.
Congratulated myself, then evaluated results. Maybe a 20% reduction in sound transmission, but still utterly unbearable for fellow home dwellers. Was I as meticulous as I could have been? Probably not, but the lesson is that unless you've got an elaborate plan, lots of money and serious OCD, SOUND WILL FIND A WAY OUT. Although I sheetrocked over all HVAC ductwork, that still proved to be the perfect mechanism by which sound was distributed throughout the house.
Update: Built a dream house in the country on three acres. I made a detached studio about 100' from main house. It's made of cinderblocks whose voids are filled with sand. Stucco on both inside and outside for slight extra sound control and aesthetics. Lots of acoustic treatment inside, but that's for sonic treatment, not soundproofing. Double pane fixed frame windows to eliminate leakage. Double doors to outside. Completely separate HVAC system which has wall penetration on the back side of the building from the main house.
Result? Family can still hear jamming, but it's quite subdued and easily overcome by moving to a less adjacent room, or watching TV or listening to another sound source.
Both next door neighbors (I'm not making this up) are musicians with their own studios, so we largely forgive each others' sonic excesses.
Bottom line: it took a detached building, built massively, with lots of air between it and other structures to bring sound down to a manageable levels. To retrofit a space within an existing structure and sufficiently isolate it from the rest of the building which shares common framing is an enormous task. I've been to studios in NYC where they've achieved it, but it took hundreds of thousands of dollars, experts, low-error-tolerance carpenters/engineers and the commitment to building a room which acoustically floats inside the "outer" (original) room. In NYC, this usually means a room that is several feet larger in every dimension that the resulting isolated space.
Like bass traps, diffusors etc.
cool
