How Does Soundproof Drywall Work?

a room with drywall

Soundproof drywall can be effective in helping to soundproof a room. Although no room can be totally soundproof, testing has revealed that soundproof drywall will actually provide soundproofing to a level in excess of standard soundproofing.

What Is Soundproof?

Soundproofing is measured by a sound transmission class (STC) rating. A rating of 40 is generally deemed to be soundproof and this measures how much sound passes through a wall. With soundproof drywall, the STC rating usually runs between 50 and 55 which is well above the standard soundproof level. This shows that it does the job very well. At that level, you wouldn’t be able to hear someone speaking on the other side of the wall.

Damping Sound

man playing an instrument

Because sound is made up of vibrations, the theory behind soundproofing works on the principle that if you can dampen the sound, you can actually reduce the volume. Soundproof drywall takes that theory and uses a technique called constrained layer damping. There’s actually nothing new about this but there are changes in the way the theory has been applied. Previous applications were restricted to industrial or construction fields such as reducing the noise of bridges over highways or the sound of airplane engines. It’s now being applied to make soundproof drywall by using a creative process.

Making Soundproof Drywall

Drywall is made of gypsum. To create soundproof drywall, layers of gypsum are alternated with layers of other materials such as plastic polymers or glue. Depending on the manufacturer, those layers could also comprise of metal or ceramic materials. The intention is to stiffen the drywall. If there’s less vibration, there will be less sound and the drywall will be more soundproof.

This is in contrast to most drywall which vibrates very easily even though you can’t see it. It tends to amplify rather than dampen the sound. Soundproof drywall is thicker than most standard drywall and is around 5/8 inch thick. Because it’s made sturdier by the additional layers, it won’t vibrate in the same manner.

Installing Soundproof Drywall

theater room

Soundproof drywall will cut in the same way as regular drywall and comes in standard sized sheets of 4 feet by 8 feet. The thickness can make for a tougher installation, especially with electrical outlets. It’s attached to studs and the sheets are joined in the same way. You use the exact same finish on it that you would on drywall. However, the cost of soundproof drywall is going to be very off-putting for most people and means it will be restricted to special projects. The price is much higher than standard drywall.

Extra Soundproofing

There are those who advocate adding soundproof drywall over an existing layer of drywall. This can be effective as part of a strategy to give sound isolation to a room. However, you’d also need to put acoustic insulation between all the studs in the room and around any door frames for maximum effect. If you’re doing this, you can’t afford to leave any gaps as the sound will leak. Most people, however, would never need a room like this.