Bigerock, read the sticky's on "complete section", as well as the one on "floated floors" - there's more than just floor info there, some is applicable to your situation.
Cadesigner (Rick) showed you the correct way to get the best isolation you can get - any time you have more than two centers of mass between you and the noise (or vice versa) you LOSE performance. You want ALL the mass in your walls to be in only two places, with only one air/insulation gap between them. So, for a double framed wall (best isolation of any framing method) you would only have wallboard (several layers) on the inside of the inner frame, and the outside of the outer frame. Where the outer frame is the outside wall, you would use OSB and siding, etc, for your mass - then, the inner mass can be multi-layer gypsum.
Most of this is covered in the Sticky section at the top of this forum.
Z, the original comment was in regards to ceiling joists; my answer was in that vein. Span tables for ceiling joists don't even LIST 2x2's...
Big, on your question about leaves - check this out -
http://www.domesticsoundproofing.co.uk/tloss.htm
scroll to the very bottom of the page, and check out the graphic showing different wall constructions -
Note that the 33, 36, 57 and 63 STC walls are all double leaf walls - the 50 dB wall is a triple leaf, and the 40 dB wall is a quad leaf wall (4 different places where wallboard is placed, with air space between)
Also note that the EXACT same amount of material is used in the 40 dB wall as in the 63 dB wall - the only difference is WHERE it's placed. Also note that every time you REMOVE material that has created an extra leaf, you IMPROVE the wall's performance. These are all tested designs, not smoke and mirrors. This one graphic is probably the best argument for proper construction on the web... Steve
Hope you have better luck than I. Of course, I didn't have resources like this fine forum and Steve......YEA STEVE!! Your a godsend for people like me. Thanks a million.