How Can I Block Noise From a Shared Wall?
Updated
Block noise from a shared wall by sealing its leaks first, because one unsealed 1/8 in. gap 1 ft long drops a wall from STC 46 to 36 in PABCO's Sound Design Guide (opens in a new tab). Then add mass, and only decouple one side if you're able to rebuild it.
- Seal: pad every outlet box on the shared wall with acoustic putty, caulk the gap at the wall base behind the baseboard, and fill any pipe and cable holes.
- Add mass: a second 5/8 in. drywall layer took an insulated 2x4 wall from STC 34 to 37 in USG's lab tests (opens in a new tab). It helps, but not a lot.
- Decouple: stripping your side and rehanging the drywall on resilient channel took that same wall to STC 48. One screw through the channel into a stud undoes it. NRC Canada calls rigid connections "the acoustical equivalent of an electrical short circuit" (CBD-239 (opens in a new tab)).
Watch out: acoustic panels and furniture against the wall barely help. A 2 in. fiberglass panel weighs about 0.5 lb/sq ft (3.0 lb/cu ft x 2 / 12 for Owens Corning 703 (opens in a new tab)). That's under a quarter of the 2.2 lb/sq ft in a 5/8 in. drywall layer (USG (opens in a new tab)), and that layer only bought 3 points. The soundproof panels guide explains why absorbers don't block.
Renting and can't open up the drywall? Stop at step 1 and check out the removable options in soundproof panels for apartments. If the real issue is a person and not the wall, how to soundproof against loud neighbors covers the other routes, and the soundproof panels FAQ has more answers.