Does Soundproof Drywall Really Work?

Installing Drywall In a Room 155387955
Installing drywall in a room. Jodi Jacobson/Getty Images

If you have ever had problems with sound next-door (or if you have been the problem), you may be interested in soundproofing your home.

One way to soundproof is to layer-up your walls with ordinary drywall. Another way is to use a specialty sound-dampening product like QuietRock.  

What Is It?

QuietRock is a sound damping drywall that manufacturer PABCO (owner of QuietRock since August 2013) says, "...was the first manufactured sound damped panel on the market," having been introduced in 2002.

QuietRock's new entry-level panel is model #510, which replaces their classic #500.  This is their lowest-cost 1.5" panel and it is designed for do-it-yourselfers. It is available at Lowe's Home Improvement.  

Composition

Creating multiple layers of materials is a sure way to deaden sound transmission.  QuietRock works on the same principle.

QuietRock is a three-layer sandwich:  two layers of approximately 1/4" drywall with a sheet of "viscoelastic sound-absorbing polymers" in the middle.

In crude terms, this middle layer can be thought of as "rubber."  But this is not quite accurate, as viscoelastic materials (such as Sorbothane) dissipate energy better than any synthetic rubber or polymer.

It is a special material that combines the elasticity of synthetic rubber with a viscous (sticky and thick) quality.  Elastic + viscous = viscoelastic.

Does Soundproof Drywall Really Work?

Yes.  Any brand of soundproof drywall will always limit sound absorption more than a similarly sized sheet of conventional drywall.

 

However, be aware that the degree of sound absorption may not be as much as you might expect and that sound absorption ratings rely on other materials, not just on the soundproof drywall.

STC Ratings Are For Wall Assemblies, Not Panels 

Drywall panels, both sound-dampening and conventional, are rated for Sound Transmission Class (STC).

 Higher STC numbers mean better sound-proofing.

But STC ratings are not for single panels.  They are for entire wall assemblies: usually 2 layers of the soundproofing drywall; studs; insulation.

Look at how QuietRock compares to a typical interior wall constructed with conventional drywall:

 QuietRockDrywall
Wall AssemblyOne layer 1/2” QuietRock® 510 gypsum panel applied vertically on each side of 2 x 4 wood studs.  Glass fiber insulation (3 1/2") is installed in the stud space. 1 /2” CertainTeed drywall (one layer) on each side of 2 x 4 wood studs. Mineral wool insulation (3 1 /2”) is installed within the cavity. 
STC Rating5234

Cuts and Scores Like Normal Drywall

Even 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.

What About Multiple Layers of Drywall?

Eight layers of standard drywall equal one layer of QuietRock #510. 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.).

 With ceiling, it's not even possible to hang multiple layers of drywall, because this adds too much weight to the joists above.

Cost

Currently, the cost of QuietRock 510 is about $52 per 1/2" thick, 4' x 8' panel at Lowe's.

Also from Lowe's, the cost of one sheet of conventional 1/2" thick drywall is $11.00.

This means that you can purchase nearly 5 sheets of conventional drywall for the cost of a single sheet of QuietRock #510.

Comparing the two products on the basis of STC ratings, soundproof drywall would be the wiser purchase because it allows you to pack in greater sound absorption in a smaller size.  

Not only that, layering up more than two sheets of drywall becomes logistically difficult.  Electrical box extenders do not extend past 1/2".  Plus, it becomes difficult to extend other building items, such as baseboards, crown molding, window sills, light switches, etc.

Fun Fact

QuietRock works up to Model #545, a commercial-grade, sound proof drywall panel with excellent sound isolation in high-end theaters and studios. 

It is interesting to note that, with its previous owner, Serious Materials, it was called Model #545 THX. True to its name, this was a THX™ sound system-certified drywall licensed by THX Ltd. sound systems, itself owned by George Lucas' Lucasfilm Ltd.