Double width studs for isolation?

One of the principles of reducing sound transmission through a wall is to add mass. Unfortunately, walls are already heavy, and to make a big improvement you have to add a lot of mass.

According to the greengluecompany.com which has done these kinds of tests in independent laboratories, "to improve sound isolation by about 10db you would have to quadruple the number of drywall layers on your wall - from one each side, to four on each side." Adding mass combined with other methods is far more effective.

I suspended a ceiling consisting of 2 layers of 5/8 drywall with Green Glue in between and suspended on sound clips, and achieved over 35 db reduction in sound in the room above. I highly recommend you read the their entire web site before making your decision.

Staggered/double studs plus 2 layers of super-dense drywall (Firewall) both sides as well as fibreglas internal insulation will give the best sound-insulation for the adjoining room. This sound-insulation is called STC (Sound transmission Class) Rating. Compared to a normal drywall with say 37 STC rating, the described wall can double the sound-proofing capabilities up to 60 STC.
STC Ratings
Study Diagrams

I've been seeing ads from a company offering rolls of sheet vinyl. They suggest covering your inner walls with the stuff prior to covering with sheet rock.
Sounds good to me...

Correction.....I am getting old!?
STC Ratings are in Decibels (dB) and thus are logarithmic.
Therefore the improvement of 37STC to 60STC is more than a TRIPLING in acoustic performance.

Good best for isolation is to STAGGER the studs. also, most code is 16" on center. There are various products to weave Between the studs as damper. DO NOT use styrofoam. It is toxic as hell when it burns, and probably against code. The products I have seen are Very heavy plastic.....I have no idea how they do it, but this stuff is pretty heavy, providing mass while meeting burn/self extinguising requirements.
By staggering, you DeCouple the walls 'sharing' the studs.
Just looking up, Elvick calls it 'insane'......Nope, just 'sound' engineering. pun intended.