A proposal for systematic investigation of reproducibility deviations in Laboratory Acoustical Measurements.

Abstract

Cases have been observed in airborne sound isolation and impact noise insulation testing where apparently identical assemblies have achieved significantly different STC and/or IIC ratings, not only when tested at different test facilities but also when re‐tested in the same facility [J. LoVerde and W. Dong, J. Acoust. Soc. Am. 125, 2629 (2009); J. Acoust. Soc. Am. 123, 3504 (2008)]. Acoustical test data will be presented demonstrating several cases and showing that the deviations are significantly larger than the expected statistical variation based on the reproducibility of the test method as reported within the applicable ASTM standards. The reason(s) for the variation in these test results are unknown, and there has been no systematic investigation of possible causes. Standards committees, test laboratories, and government agencies have not shown a satisfactory level of interest in either quantifying the deviations or exploring the reasons behind them, which may be theoretical, material, and/or procedural. A protocol is presented for a se‐ries of investigations that could be performed in an acoustical testing laboratory intended to identify and quantify causes of the variations.