Methods for validation of electromechanical evaluation of hearing protection

Preventing hearing injury while maintaining situational awareness is of critical importance while using hearing protection devices (HPDs). Determining the optimal HPD for such varied conditions as operating machinery, riding in aircraft, and using firearms is a non-trivial task. Currently, the Noise Reduction Rating (NRR) is the only required HPD specification; other important characteristics of advanced HPDs are not reported in a standardized manner despite the availability of relevant test standards. Barriers to standardized performance reporting are the use of human subjects and the range of performance capabilities of commercially available HPDs. To complement existing test standards and support standardization of performance reporting across a broader range of performance capabilities, a suite of quantitative, sensor-based tests is being developed to quickly, inexpensively, and comprehensively evaluate candidate HPDs. The five-test battery evaluates signal quality, sound localization, level-dependent frequency response, electronic self-noise, and impulse noise response. In parallel, a set of human subject tests is being developed to validate the electromechanical metrics. Here, we will present (1) preliminary results comparing human performance with complementary electromechanical data and (2) a software tool under development incorporating the electromechanical tests to optimize HPD selection for application-specific hearing protection.