A viscoelastic damping compound applied between two layers of drywall converts vibration into a tiny amount of heat. It is most useful where there is no room to decouple, and it helps at the low-mid frequencies where walls resonate.
- Typical gain: 5–10 STC over the same double-layer wall without compound.
- Apply per the manufacturer's coverage rate, then screw the second layer on within the working time.
- Works on existing walls: add a new layer over the old one.