Comparative measurements of the performance of hearing protectors with an ATF are useful for the development of national and international standards also, the methods in the American National Standards Institute/Acoustical Society of America (ANSI/ASA) S12.42 standard are still being refined to understand the assessment of hearing protection when exposed to high-level impulse noise. This study utilized two models of the same ATF to measure the impulsive response of four hearing protector conditions. This paper reports and compares the measurements obtained with both fixtures. The Methods section describes the construction of the test fixtures, the acoustic impulse source, the hearing protectors used as well as the data acquisition system and analysis methods. In the Results section, the impulse waveforms are described and the results for each of the hearing protector conditions and the statistical analyses are presented. In the Discussion section, the effects of the fixture position, ear canal length, and the performance of double protection are discussed.

NIOSH and 3M E-A-RCAL both purchased acoustic test fixtures from the French-German Research Institute of Saint-Louis (ISL) built following the publication of the ANSI/ASA S12.42-2010 standard.

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