Sound Transmission Class: wall
Sound Transmission Class (STC), Impact Insulation Class (IIC), and Outdoor-Indoor Transmission Class (OITC) ratings for building assemblies — walls, floor-ceilings, doors, windows, partitions — per ASTM E90/E413/E492/E1425
| assembly type | assembly id | STC rating (dimensionless) | assembly description | construction detail | fire rating hr (hr) | frequency weaknesses | thickness in (in) | weight psf (lb/ft2) |
|---|---|---|---|---|---|---|---|---|
| wall | wall_cmu_8in_furring | 52 | CMU wall 8 in with furring and gypsum | 8 in nominal CMU (ungrouted); 3/4 in Z-furring strips on one side; 5/8 in gypsum on furring; air gap; opposite face exposed | 1.5 | Air gap decouples gypsum from CMU; mid-freq flanking reduced; practical upgrade | 9.5 | 33 |
| wall | wall_cmu_8in_grouted | 53 | CMU wall 8 in fully grouted | 8 in nominal CMU fully grouted; normal-weight grout 140 pcf; both faces exposed | 0 | Mass law governs; coincidence around 500-800 Hz reduced with grout mass; very robust at high freq | 7.5 | 75 |
| wall | wall_cmu_8in_ungrouted | 44 | CMU wall 8 in ungrouted | 8 in nominal CMU ungrouted; both faces exposed; 70 pcf LW block | 0 | Low-freq weakness below 125 Hz; coincidence ~800 Hz for hollow CMU; leakage at mortar joints | 7.5 | 30 |
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