Pro amplifies soundproofing suggestions

As a home theater designer by trade and a woodworker by hobby, I was pleasantly surprised to see such a well-done article about sound dampening in issue 277 (October 2021). I especially commend you on recommending the use of hat channels with isolation clips—something that many people forget to mention—and to avoid attaching anything to studs. Please allow me to add to your article based on my experience.

First, instead of using two layers of 5⁄8" drywall, I layer one each of 5⁄8", 3⁄8", and 1⁄4" drywall, as shown, right, alternating horizontal and vertical orientation between layers. I find it easier to glue the 1⁄4" up first to the hat channel or stud, then glue the 3⁄8" to that (I like Green Glue on this layer if budget allows); then screw the final 5⁄8" layer through all three. This minimizes the number of screws in the wall and, because each thickness of drywall has a different frequency range of sound control, you get more rounded sound blocking.

Also, instead of mounting electrical boxes to the studs, I pigtail the electrical lines out of a 1" hole in the drywall and use remodel (“old work”) boxes at the end. These are designed to be added after the wall is completed, so they can go anywhere there isn’t a stud, and they simplify drywall installation since you don’t have to cut accurate electrical box openings multiple times. (But you may need to bend a tab a little, if it hangs up.)

I don’t recommend fiberglass batt insulation for sound insulation because paper-backed fiberglass insulation creates a double vapor barrier that can lead to moisture problems down the road. The best sound-dampening product is rock wool: It installs easier, it’s almost impossible to compress to the point that it loses its sounddampening abilities, and you can double it up in a double wall.

Finally, the most overlooked area in sound dampening is the ceiling above. You can follow all of the best practices on the walls, but a single heating duct in the ceiling negates it all. It’s important to look up and use some common sense here, too.

Again, a great article from an unexpected source. Well done, WOOD magazine!