I used Celotex soundboard (I think their trade name is SoundStop)in the wall of my theater shared with the house. After I insulated the cavities between the studs with standard R19 fiberglass, I screwed the SoundStop up like drywall. It cuts easily with a sharp utility knife. Be careful with your screw gun... this stuff is soft. I didn't seal the joints with anything; it might have been a good idea to use caulk of some sort. Then I drywalled over it as usual (with longer screws, of course). Make sure you plan ahead for the additional 1/2" of wall thickness when setting electrical boxes, doors, etc.
I think the SoundStop was a cheap and easy way to gain 4-6 dB of attenuation; don't expect SoundStop to make the room "soundproof". If you're using it in exterior walls, you'll also welcome the additional R-value. It's probably not a lot, but in Tempe in July, every little bit helps...
Your post is a bit crytic, but if you're interested in noise control, get a copy of Owens-Corning's "Noise Control Guide" and "Insulations for Mechanical Systems", Pub #s 5-BL-21971 and 1-IN-14210-K, or their replacement.