A new metric for evaluating mid- and high-frequency impact noise

Abstract

Impact isolation within multi-family dwellings is currently evaluated using the single number laboratory metric Impact Insulation Class (IIC) and associated field test metrics. There is wide acceptance that IIC does not adequately quantify low frequency impact noise such as thudding from footfalls which is prevalent in lightweight joist-framed construction. However, it is often assumed that mid- and high-frequency impact sources, such as heel clicks, dragging furniture, and dropping objects, are adequately characterized by IIC. Previous research by the authors have indicated that IIC does not adequately distinguish or rank-order between the acoustical performances of resilient matting located in the upper room of a floor ceiling assembly [LoVerde and Dong, J. Acoust. Soc. Am. 120, 3206 (2006); LoVerde and Dong, Proceedings of ICVS14 (2007)]. Many condominiums have regulations that require a minimum impact sound rating when replacing or installing hard surface finish flooring, and may require field testing to show compliance with the regulations. As expected, a field IIC metric like AIIC, NISR, or ISR is not a suitable descriptor for acoustical performance. A modified metric is defined that more accurately rank-orders the mid- and high-frequency impact noise performance of assemblies and is better suited for these performance requirements.