| Layers | Typical lab STC | Relative cost |
|---|---|---|
| Two rows of 2×4 studs with a 1 in gap, insulation in both, 5/8 in each side | 56 | $$$ |
Common for party walls in townhouses. Loud music is barely audible and speech is inaudible.
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.