Uncertainty of ANSI/ASA S12.42 Hearing Protection Device Impulsive Measurements

ANSI/ASA S12.42 was extended in 2010 to include methods for measuring the performance of hearing protection devices (HPDs) in impulsive noise conditions. The standard specifies the instrumentation, methods, and data analysis required to measure impulse peak insertion loss (IPIL). IPIL is defined as the amount by which an HPD reduces the effective peak level of an impulsive sound. To characterize HPDs whose attenuation may be level-dependent, IPIL is measured at several impulse peak sound pressure levels, typically in the range of 130-170 dB. Factors contributing to the uncertainty of IPIL measurements include repeatability in the generation of test impulses, variability of the HPD samples under test and their repeated fitting to the test fixture, and spectral properties of the impulse source and the HPD’s attenuation. To help inform future revisions to the S12.42 standard, we quantify IPIL measurement uncertainty for a variety of HPDs tested with two different impulsive sound sources. End users of HPDs should be educated about the uncertainty inherent in IPIL assessments of HPD performance.