Korling Construction: Soundproofing

I grew up in North Hollywood, where set builders and prop shops were everywhere. Musicians came and went. Most musicians were carpenters too. I had plenty of experience building sound rooms, growing up where I did, but with technology and precise building, things have changed.

Recently a client, musician Sapphire Adizes, hired me to design a soundproof room for him so he wouldn’t bother his neighbors.

When I was building soundproof rooms years ago we did it the old-fashioned way: We filled the walls with sand all the way to the top. The only problem was that eventually the sand would leak through the wall or attract moisture. A more advanced soundproof room would have solid concrete walls, but that’s not affordable.

To understand soundproofing, imagine throwing a golf ball into a cotton canvas. The canvas has to move or give in order for the golf ball to quietly interact with it. When building a soundproof wall we need to create a “canvas” on the inside of the noisy room. The exterior walls are not as important because the interior wall is doing all the work of softening the noise. (Although four layers of drywall on the exterior wouldn’t hurt.)

Here is the method we use today:

1. After our 2x4 walls are built (whether the studs are steel or wood doesn’t matter), we install rubber metal clips on the studs. These rubber metal clips will receive the metal tracks in step 2. The rubber on the clips gets screwed directly onto the 2x4 studs. That creates the give or movement that we need to silence the noise.

2. Once the rubber clips are installed, we snap on long metal tracks called “hat channels,” because they look like a little hat. These tracks basically create another wall between the original 2x4 wall and the drywall. The hat channels/track must run horizontal across the 2x4 stud wall, 3 inches below the ceiling and 6 inches above the floor.

3. Once we have installed the hat channels, we can install 5/8 drywall on top of the metal track/hat channel. Some tracks and rubber clips allow you to install only 2 sheets of 5/8 drywall, but there are different ways to set up the tracks and clips to allow a builder to install 4 layers of 5/8 drywall. A sound engineer or structural engineer should be consulted first to make sure you have the correct specifications. On the walls, the extra drywall wouldn’t be so dangerous, but a ceiling that is too heavy with drywall can hurt or kill someone.

The drywall on the walls should be at least 1/4 inch to 3/8 inch off the floor. The drywall on the ceiling should hang away from the 2x4 walls as well. This gap allows a lot of movement between the interior drywall and the exterior wall, adding to the noise reduction. Four sheets of drywall is quite enough to muffle most noise and keep it from passing through to the exterior walls. Again, it’s essential to have the correct spacing, amount, and gauge of rubber clips and hat channels to support four layers of drywall.

The interior walls, where the noise is being made, are the most important in reducing noise. The exterior walls are not as important.

In addition to the soundproof room, Sapphire Adizes also needed to get a more dense sound in his recording room (removing the echo). To accomplish this we installed 2-inch and 4-inch acoustical foam on all the corners of the room, including the ceiling. Another approach would have been to rebuild the room with 45-degree angles on the ceiling, which also deadens the echo.

Always consult with your engineer, architect, builder, and sound engineer, and the local city codes before building.

You can check out more projects like that on our website www.Korling.net