How Close to abosultely soundproof can I get...and how ?

Hi Everyone: this looks like a great forum and very helpful so I thought I would give it a try. I just moved into a new (old) house and I want to convert the small single car garage into a studio/jam/rehersal room with a set of drums, bass and a couple of guitars. The room will be small as I am limited to approx 9 ft x 15 ft and a ceiling height of 11 ft finished space once I build the room in a room concept. One problem is my sons bedroom is directly above the garage and I unsually would start making sounds at about 11pm at night when he's asleep. The other problem is its a very quite neighbourhood I moved into and I don't think the neighbours would appreciate my musical tastes, even less at 2 am in the morning! I did place 9-1/2 inches of roxul insulation between the floor joists in the garage ceiling in anticipation of creating this room which I am now ready to build. The garage floor is a concrete slab on grade and surounded by footing as the rest of the house is above a crawlspace about 3 feet above the garae floor slab. My goals are to achieve as soundproof a room as possible as to not wake him up, nor the neighbours at 2 am as well as try to keep the budget reasonable. I typically like to play hard rock type of music (which doesn't help either...). I'm not overly concerned with recording in the room, but rather sound isolation (as absolute as possible). The questions I have are: 1) What are the best means and methods to achieve this goal. 2) Do I need a floating floor or would the existing concrete slab on grade deal with most of the low frequencies from drums and bass (maybe I could sawcut the slab to isolate it from everything else ?)? 3)I was planning to roxul the perimeter garage walls (2x4) and then 1/2" drywall, resilient channel then 5/8" drywall. then I would build a room inside the garage 9' x 15' x height? using a 2x4 or 2x6 stud with roxul insulation and 2 layers of drywall to eachside with each layer being separated by a res-bar to decouple it. I also thought that I could use a membrane on the slab to try and decouple the floor from the room. I would also acoustically caulk the penetrations and try to limit the number of penetrations by keeping all electrical wiring, boxes, etc. within the room. I also thouoght that I would res-bar the existing garage ceiling and drywall it and then create another roxul insulated ceiling over the room itself with a drywal/res-bar/drywall type of system. Is this going to get me close to my goal or would this be unnecessary work or is this just a pipe dream. Any help or advise would be much appreciated. Thanks

You need to study up on soundproofing. My advice is to get Rod Gervais' book (linked in the stickies on this forum). Also, read the "Do I Need A Floating Floor" thread, also in the stickies. Make 100% sure you understand the "2-leaf" concept. I'd look through Sharward's build thread to understand this fully (as well as Rod's book). In short, soundproofing is about mass, airtightness, and specific construction techniques. You won't get 100% soundproofing, but with enough budget and attention to detail on your build you could make it workable for your son above you.