Development of a two-parameter system for evaluating impact noise insulation

Abstract

Impact insulation is currently described with a single number metric impact insulation class (IIC), which correlates poorly with subjective reaction and does not often properly rank order acoustical performance of assembly components. Modifications to IIC have been proposed, but the methods are limited to changing the source or the metric. Experience indicates that impact noise can be divided into two broad classes: Low frequency thudding (e.g., footfalls) and mid/high frequency noise (e.g., heel clicks, dragging furniture, etc.). Low-frequency impact sound pressure level (ISPL) is generally influenced by different variables than the mid/high-frequency ISPL; the authors propose that the two are largely independent. Therefore, two domains are required to adequately characterize the impact noise insulation of an assembly [LoVerde and Dong, 33rd Inter-Noise Proceedings Paper 296, 167 (2004)]. A variety of candidate two-domain systems have been reviewed, where one domain describes the low-frequency performance and the second domain the mid/high-frequency performance [LoVerde and Dong, 14th International Congress Sound and Vibration Paper 476 (2007)]. The two domains are calculated using third-octave ISPL data obtained from recent field impact noise tests. The results suggest that a two-domain system offers considerable improvement over current single-number metrics for evaluating and designing assemblies.