Evaluation of mid- and high-frequency impact insulation methods

Impact insulation is currently measured using impact insulation class (IIC) and a standard tapping machine described in ASTM E492 and E1007 (and corresponding ISO metrics and standards). The resultant IIC value does not correlate well with subjective reaction. In previous papers, the authors have focused on the low-frequency thudding from footfalls in lightweight wood construction and shown that the impact sound pressure level (ISPL) in the 63-Hz octave band correlates better with subjective reaction than IIC or other metrics [LoVerde and Dong, J. Acoust. Soc. Am. 112, 2201 (2002); INCE Inter-Noise 2004 Proceedings, 167 (2004); J. Acoust. Soc. Am. 119, 3220 (2006)]. Further, the low-frequency ISPL is controlled by different variables than the mid/high-frequency ISPL. This suggests that a two-metric system would be valuable where the first metric describes the low-frequency performance and the second metric describes the mid/high-frequency performance. Field testing experience is presented showing that IIC does not adequately differentiate the mid/high-frequency performance of various resilient materials. Candidate mid/high-frequency metrics are evaluated to determine if any result in improved methods for evaluation and rank-ordering of floor/ceiling assemblies.