| Layers | Typical lab STC | Relative cost |
|---|---|---|
| 2×4 studs, insulated, 2 × 5/8 in Type X each side | 45 | $$ |
Good mass upgrade without changing framing. Loud speech is barely audible.
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.