Acoustic panels improve sound inside a room. Stopping sound passing between rooms is a different job measured by STC (Sound Transmission Class). For stores, aim for walls of about STC 45 for fitting rooms and offices.
| STC | What you hear through the wall |
|---|---|
| 30 | Normal speech easily understood |
| 40 | Loud speech heard but not understood |
| 45 | Loud speech barely heard |
| 50 | Loud music faint, speech inaudible |
| 60+ | Most sounds inaudible |
How to reach STC 45
- Add mass: a second layer of 5/8 in drywall. See mass law.
- Decouple the two sides: resilient channel, staggered or double studs. See decoupling.
- Fill the cavity with mineral wool insulation.
- Seal every gap with acoustic sealant, and treat outlets and doors. See flanking paths.
Compare real wall assemblies in our STC assembly guides.