QuietRock starts with model #510, their lowest-cost product, and works up to model #545 THX, which, true to its name is a THX™ sound system certified drywall for excellent sound isolation in high-end theaters and studios.
Cuts and Scores Like Normal DrywallEven though QuietRock is denser than conventional drywall, it can still be scored and snapped (or cut) in the same way with a standard utility knife.
QuietRock is Not 100% Sound-ProofEven though Serious Materials' sales literature does use the term "soundproof," no material is truly soundproof. Anyway, "soundproof" is a misnomer. Except for the vacuum of space, nothing is 100% soundproof.
However, when you look closer at QuietRock's specs, it becomes clear that sound dampening, absorption, and mitigation are the goals of QuietRock.
Better Than Multiple Layers of DrywallEight layers of standard drywall equal one layer of QuietRock #525. So, theoretically you can hang multiple layers of drywall and achieve the same effect.
But realistically this will not happen. Multiple layers of drywall have these problems: increased weight on your walls; added cost; receptacles need to be bumped out; floor space is lost; higher labor costs; higher ancillary materials cost (joint compound, drywall tape, etc.).
Cost of QuietRockEven though Serious Materials advertises a cost of $39.95 for a single 4'x8' sheet of QuietRock #510, this is for bulk purchases. True costs run much higher.
Let's say that you can buy a sheet of conventional drywall for $8.00 at The Home Depot. Eight sheets of this drywall at $8.00 would exceed the cost of a single sheet of QuietRock #510.
You need to look at total cost rather than sheet cost. Hanging multiple sheets of conventional drywall (even if logistically possible) will also drive labor costs higher than if you were to hang single sheets of QuietRock.