Auralex Sheetblok Sound Barrier

SheetBlok Sound Isolation Barrier is a dense, limp-mass vinyl material that is about 6dB more effective than solid lead at stopping the transmission of sound. It acts as a thin, dense sound barrier layer in walls, ceilings or floors and is most effective when used as one component of a multi-layered construction scheme.

SheetBlok helps in decoupling (i.e. floating) floors and walls and, while it's not normally considered a finish product per se, it is paintable with latex paint.