| Layers | Typical lab STC | Relative cost |
|---|---|---|
| 4 in solid brick, mortar joints full | 45 | $$ |
Older buildings; seal gaps in mortar. 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.