Studio wall construction

[laptoppop]

OK, I've read lots of different things, but I can't figure out the best answer.

I'm trying to add some sound isolation to a room at the back of the house...for the least cost for reasonable benefit. Its about 21x17 feet, and is covered with normal residential construction -- one layer of wallboard over non-staggered studs.

What will give me the best improvement in keeping sound from the outside out and inside sound in?

1) Adding another layer of wallboard mounted on resilent channel
2) Adding a layer of plywood with a layer of wallboard over that
3) Two layers of wallboard over the current layer
4) ????

I'm leaning toward number 2. Adding a LOT of mass, such as a brick wall, is not an option. I'm thinking that the dissimilar materials would help. I'm not sure how THICK to make the plywood. I suspect that even a thin layer will work well, but of course, the thicker, more massive layer would work better. I've been looking, but I haven't found STC numbers for different thicknesses of plywood.

So, what should I do?

Thanks,
-lee-

[John Sayers]

I'd go for No 1. using 5/8" drywall.

I asume by wallboard you mean drywall/plaster. I'd also have insulation 1" between the two layers.

cheers
john

[laptoppop]

OK, John - you're the man!

Sooooo, I'm going to put up resilient channel and wallboard with 1" of insulation on top of the existing wall, and possibly on top of the existing ceiling -- we're seeing if we open that up to the attic space or not.

Question for the board: Whats the best resilient channel to use? Where can I buy it cheaply?

Thanks!
-lee-