We hear terms like Mass Law, Mass Loaded Vinyl (MLV), Massive Drywall, and one could conclude that mass is the only thing we’re after to soundproof a room. This is only partly true. This website has a very good discussion going regarding this topic. House Repair Talk Forum
Essentially mass is not the only factor to consider with soundproof construction. It’s what you do with the mass that is key. There are many examples where mass is increased and performance does not increase. Understanding the Triple Leaf articles described the issues involved in such an assembly.
It’s how you assemble the available mass that defines your success in your sound isolation and soundproofing efforts.