Double width studs for isolation?

1. Studs should be 16" on center.
2. Use 2X6 lumber (Good, but not essential).
3. Apply 1/2 inch sheet rock.
4. Apply a layer of styrofoam (or other lightweight plastic insulation panel). One inch thickness is fine.
5. Apply another layer of 1/2" sheet rock.

5/8 sheet rock is to avoid sags between ceiling rafters which are on 2 foot centers.

Schipo...I believe that if the styrofoam is sandwiched between sheetrock layers it's safe. Exposed to air inside a wall is a problem.

Nsgarch...I too went to MIT, but was more interested in women than calculus. Tech Hi Fi in the warehouse also, Graduated elsewhere; Pratt Institute of which, as an architect you are probably aware.

As to acoustic isolation, my expertese is that I actally did a room with the foam insulation sandwiched between sheet rock. I did it for thermal insulation, but was astonished by the acoustic isolation result.

Stagered studs have pros and cons. It minimizes direct transmission through the wall, but, with sheetrock on only one side of the studs the walls are not very stiff.

Nsgarch...I have built many 2X4 interior walls, and they are almost floppy until you get the sheetrock on the second side.

Elevick...When working on a 200plus year old house (like mine) studs are where you find them. Often they are rock hard hemlock that you can hardly get a straight nail into. Makes life interesting.