Double width studs for isolation?

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.

Magfan, I totally understand the "sound" engineering. However, having renovated many buildings, I know what it's like to have to open up walls to search for studs. That's why I'd push for either 16" studs with random in between or at least a pattern to aid in future finding of the studs?
If I was buying a property with random studs this would greatly devalue the property and would be considered a "knock" down on any wall unless plans were available with exact dimensions and proof of proper construction by a qualified contractor.

Also, I've never seen it in a store, but on some home reno shows on HGTV, I've seen a new type of sound absorbing drywall. It's a bit expensive. I believe it has a sheet of metal sandwiched between layers of gypsum. It might work through the stiffening effect that Nsgach noted. Maybe you can find it somewhere. Try the websites for drywall manufacturers.
Markphd 02-07-09

Quiet Rock, 545 THX
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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.