, Updated
Impact noise is the sound created when something strikes a floor, such as footsteps or a dropped object, and travels through the structure to the room below. It is not voices or TV travelling through the air, which need a different treatment. An underlayment placed beneath the floor finish or under the screed reduces impact noise; it does not make the room below silent.
What Lw and IIC are
- Lw (per ISO 717-2): the reduction in impact sound pressure level, in dB.
- IIC (Impact Insulation Class, per ASTM E492): the impact insulation rating of a whole floor assembly; higher is better.
Why not to compare directly
Every result is valid only for the assembly that was tested: concrete slab thickness, whether there is a ceiling, and the floor finish. Compare only numbers measured under the same conditions, and always read the test conditions in the datasheet.
Examples from the datasheets
| Product | Thickness | Result stated in the datasheet |
|---|---|---|
| GenieMat FF03NP | 3 mm nominal | Lw 23 dB (ISO 717-2) |
| GenieMat FF05NP | 5 mm nominal | Lw 25 dB (ISO 717-2) |
| GenieMat RST05 | 5 mm nominal | IIC 50 over a 6 in concrete slab with 12 × 12 in ceramic tile, no ceiling |
| EnkaSonic E10 | 10 mm | IIC 59 (ASTM E989, WTCB); dynamic stiffness s’ = 30.1 MN/m³ |
Need an underlayment for a specific project? Send us the floor build-up and your acoustic requirement on the Contact page, or see the Impact sound insulation group.