| Layers | Typical lab STC | Relative cost |
|---|---|---|
| 2×4 studs at 16 in, one layer of 1/2 in drywall each side, empty cavity | 33 | $ |
Typical older interior wall. Speech passes through easily. Normal speech can be understood through the wall.
Getting the rated performance
- Build it exactly as tested; small changes (screw spacing, stud gauge) change results.
- Seal the perimeter and all penetrations with acoustic sealant.
- Carry the wall to the structure above.
Values are typical lab ratings from published test data for similar assemblies; your manufacturer's tested assembly is the authority. Field performance is usually lower: see field ratings.