What's the Cheapest Way to Soundproof a Wall?
Updated
The cheapest way to soundproof a wall is to seal its leaks with acoustical caulk and outlet putty pads, 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). Sealing gets back rating the wall already has, and you don't have to tear anything out.
Work through these in order, cheapest first. The STC numbers come from USG's lab tests (opens in a new tab) of a 2x4 wall with 5/8 in. drywall.
- Seal the base and outlets. Pull the baseboard, run non-hardening acoustical sealant along the gap at the floor, then wrap each outlet box in a putty pad.
- Fill an empty cavity. Fiberglass in the cavity took the wall from STC 32 to 34. Blown cellulose, which airport sound programs (opens in a new tab) use for sidewalls, goes in through small holes, so you're not tearing out the wall.
- Add a second drywall layer. Screw it over one side and the insulated wall went from 34 to 37.
- Decouple one side. Strip one side and rehang it on resilient channel, and the same wall jumped to 48. It's the most labor, and the biggest gain.
Watch out: acoustic panels hung on the wall are poor value here. They soak up echo in your room, but they add far less weight than a drywall layer, so they'll block less than the 3 points that layer bought. The soundproof panels guide shows which panel types block and which only absorb.
A whole room leaks in more places than one wall, and it's usually the door first. The order for that job is in the cheapest way to soundproof a room. You'll find more low-cost fixes in the soundproof panels FAQ.