Impact Sound Insulation

Impact sound insulation is the ability of a floor construction to reduce the transmission of sound caused by direct physical impact on the surface, such as footsteps, dropped objects, and furniture movement. Measured using a standardized tapping machine (per ISO 10140-3 in the laboratory or ISO 16283-2 in the field), the resulting sound levels in the room below are reported as normalized or standardized impact sound pressure levels. Unlike airborne insulation (where higher is better), impact insulation is rated by how low the transmitted level is: lower Ln,w or L’nT,w values indicate better performance. Impact insulation is improved by soft floor coverings (carpet, resilient vinyl), floating screed systems, resilient interlayers, and suspended ceilings with absorptive material. Impact sound is the most common noise complaint in multi-storey residential buildings. Building codes require IIC 50 (IBC) or L’nT,w ≤ 62 dB (UK) between dwellings. Heavy concrete floor slabs provide the best base performance due to their mass.