New Build Wall Construction
The soundproofing treatment described here targets the reduction of noise bleeding through a new wall that is not yet built. As we describe in our course on Transmission Loss here at the Academy, our goal with this sound control project is to isolate one room's noise from the next by impairing the common wall's ability to conduct vibration. The treatment prescribed below follows the basic principles required for sound deadening a wall: disconnecting the structure and lining it with weight.
We start with the illustration of a standard wall assembly. A single set of 2x4 studs are built to support drywall on both sides of a common wall. As we teach in our course on Sound Transmission, sound energy vibrates freely back and forth structurally through this common set of studs. This is called structure borne vibration. Regardless of what is stuffed in the cavity between the studs, including fiberglass insulation, the studs themselves are the true culprit for sound bleed and the focus of our treatment.
STEP 1: DISCONNECTION
Your goal with new build construction is to avoid common contact points in your wall assembly. By disconnecting your structure, you force the collapse of the structure borne sound waves inside your wall. For a new wall construction, there are two common building techniques used to create this disconnection. A double wall or a staggered stud wall which are both illustrated here:
A staggered stud wall will typically be 6" thick, alternating 2x4 studs back and forth running them flush with either side of your 2x6 base plate. A double wall is simply two separate walls standing side by side with complete disconnection. This will take more depth out of your room, but will also deliver a disconnected base plate. Both assembly's are equally effective at combating unwanted sound bleed by creating the disconnection in your common wall. The sound wave attempting to transmit through the studs will simply collapse inside the wall.
STEP 2: DENSITY
Once you've built either of these disconnected wall structures, the next step is to line the wall with density by stapling dB-Bloc to the existing face of your studs. This is a mass loaded vinyl material measuring just 1/8" thick, but weighing in at more than 150 pounds per roll. The extreme density will slow your wall's ability to vibrate, which will in turn will slow down the amount of energy the wall is able to deliver through your assembly. dB-Bloc is available in 54" x 30' rolls as is shown here:
STC values rate a wall assembly's ability to combat sound transmission. Test results for dB-Bloc in a lab setting rate an STC of 27. When applied in a field application, in conjunction with a disconnected framing technique, the STC value of a finished wall assembly can spike dramatically. A standard wall configuration will carry an average STC rating of 38, while a luxury wall assembly will boast STC ratings of 55-60. Individual results will vary depending on leakage, quality of construction, floor vibrations, ceiling plenum's, flanking paths, and a host of other factors that extend beyond the control of the treatment.
dB-Bloc is mechanically applied to your studs with staples or screws. Overlap the seams by 1-2" as you layer this material to 100% of your common wall surface. dB-Bloc can be hung horizontally or vertically. Our test results are triggered with a single layer of the material on just one side of the wall, ideally the source side where the original sound is coming from. For harsher sound sources with stronger budgets for this project, you can duplicate the treatment on both sides of the wall to trigger on average an additional 3-5 dB drop.
Your treatment sequence: wall disconnection + dB-Bloc + drywall