![]() Hearing tests are administered to these individuals with and without the protectors in place. ( 2) The NRR is based upon human subject testing conducted in the laboratory with a panel of listeners. Environmental Protection Agency (EPA) requires the single-number noise reduction rating (NRR) to be shown on the label of each hearing protector sold in the United States. ![]() Hearing protector attenuation is determined either by conducting listening tests with human subjects or by direct acoustical measurement. Factors such as the experience of study participants and test administrators, and the fit-test psychometric tasks are suggested as possible contributors to the observed results. Individual labs exhibited a range of agreement from less than a dB to as much as 9.4 dB difference with ANSI and REAT estimates. Standard deviations for residual attenuation differences were about ☒ dB for FitCheck and HPD Well-Fit compared to ±4 dB for VeriPRO. For each of the fit-test systems, the average A-weighted attenuation across the four laboratories was not significantly greater than the average of the ANSI sound field method. A-weighted attenuations measured with FitCheck and HPD Well-Fit systems demonstrated approximately ☒ dB agreement with the ANSI sound field method, but A-weighted attenuations measured with the VeriPRO system underestimated the ANSI laboratory attenuations. Differences in octave-band attenuations between each fit-test system and the American National Standards Institute (ANSI) sound field method were calculated (Atten fit-test - Atten ANSI). The NIOSH lab had the lowest average attenuations and the largest standard deviations. The Michael & Associates lab had highest average A-weighted attenuations and smallest standard deviations. The occluded fit of the earplug was maintained during testing with a soundfield-based laboratory REAT system as well as all three headphone-based fit-test systems. The Howard Leight Airsoft premolded earplug was tested with twenty subjects at each of the four participating laboratories. Army Aeromedical Research Laboratory (USAARL), which provided their data for inclusion in this report. An identical study was conducted independently at the U.S. Each system was compared to laboratory-based real-ear attenuation at threshold (REAT) measurements in a sound field according to ANSI/ASA S12.6-2008 at the NIOSH, Honeywell Safety Products, and Michael & Associates testing laboratories. The National Institute for Occupational Safety and Health (NIOSH) sponsored tests of three earplug fit-test systems (NIOSH HPD Well-Fit™, Michael & Associates FitCheck, and Honeywell Safety Products VeriPRO ®).
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