Impact sound insulation performance of floating floor assemblies on mass timber slabs

Mass timber buildings become increasingly popular in North America and worldwide. Mass timber panels are mainly used structural slabs in mass timber buildings. However, due to the lightweight and low-stiffness of mass timber panels, the human induced impact sound on floors has been identified as an issue to be solved. Floating concrete topping is a common solution adopted for insulating the impact sound transmission through the mass timber slabs. However, there is few guidance on designing floating concrete floor assemblies and high performance floating floor assemblies for mass timber slabs. In this study, the relationship between concrete topping thickness, dynamic stiffness of elastic interlayers and the impact sound insulation performance of continuous floating concrete assemblies was first investigated according to ASTM test standard. It was found that the floor assemblies with lower apparent dynamic stiffness of elastic interlayer and thicker concrete topping had higher apparent impact insulation class (AIIC) ratings, but limited under 53 dBA without additional floor finish. The empirical prediction equation overestimated the improvements of floating concrete toppings on mass timber slabs. Then, a series of discrete floor raised floor assemblies using elastic mounts were tested using the tapping machine. The results showed AIIC rating of the discrete raised floating floor reached up to 65 dBA. At last, the low frequency (50 to 630 Hz) impact sound insulation performance was conducted according to JIS standard using the ISO rubber ball. With the comparison of sound pressure level (SPL) spectra among ISO rubber ball, ISO tapping machine and real adult walking on both bare floor and different floating floor assemblies, the ISO rubber ball was found to be a suitable source simulating human foot fall noise. The raised discrete floating floor still demonstrated outstanding impact sound insulation performance. However, the correlation between corrected maximum sound pressure level (LFmax) index and apparent impact insulation class (AIIC) was very low. Overall, the floating floor assemblies had similar performance regardless of the type of mass timber slabs as long as the slabs had the same thickness and wood species.