A teen whose musical tastes run to head-pounding heavy metal classics? Uncle Ted, whose snoring would wake the dead? Who knows what’s giving Robert Car pause for thought. Whatever it is, he wants to build in some effective sound-proofing.
“I’m aware of using more than one layer of drywall,” he writes in Q&A post, “but is that the only way?”
Increase the mass of the wall
Car is reluctant to add a second layer of gypsum drywall mainly because it will, however slightly, reduce the usable space in the room.
But increased mass is part of an effective strategy for reducing sound transmission.
“Here are some good rules of thumb,” writes Robert Riversong. “When the mass of a barrier is doubled, the isolation quality (or STC rating) increases by approximately 5 dB, which is clearly noticeable. Installing insulation within a wall or floor/ceiling cavity will improve the STC rating by about 4 to 6 dB. An airspace of 1-1/2 in. will improve the STC by approximately 3 dB. An airspace of 3 in. will improve the STC by approximately 6 dB.”
A second layer of drywall, often 5/8 in. rather than 1/2 in. thick, along with resilient channel to isolate the drywall from the wall framing, increases mass and reduces sound transmission. Andy Ault, however, suggests three other options.
“We practically make this our [standard operating procedure] in walls between master baths and nurseries/adjoining bedrooms,” Ault writes of SoundStop. “We bond the SoundStop to the framing using an acoustical sealant running horizontal to the framing. Then we tape the joints with butyl tape. Next, we layer the gyp board over that in a…