Auralex StopGap Acoustical Sealant, 28 oz

Isolation fails at the gaps, and StopGap is what closes them. It is a highly elastic, water-based sealant for the perimeter of a wall system and for electrical box cutouts, the two places where flanking noise routinely undoes an expensive assembly. The surface skins over to a tough film while the body underneath stays pliable, and it holds that flexibility roughly five times longer than competing sealants, so a joint that moves with the building keeps its seal instead of cracking open.

Applied in accordance with ASTM C-919, StopGap reaches a Sound Transmission Class of 53. It is paintable, dries white, does not stain, has no residual run-off, and meets ASTM E-84 for flame spread. The tube is a large 28 oz size, so a heavy-duty caulking gun is required rather than the standard 10 oz frame.