Measurement of impulse peak insertion loss for four hearing protection devices in field conditions

Abstract

Objective: In 2009, the U.S. Environmental Protection Agency (EPA) proposed an impulse noise reduction rating (NRR) for hearing protection devices based upon the impulse peak insertion loss (IPIL) methods in the ANSI S12.42-2010 standard. This study tests the ANSI S12.42 methods with a range of hearing protection devices measured in field conditions. Design: The method utilizes an acoustic test fixture and three ranges for impulse levels: 130–134, 148–152, and 166–170 dB peak SPL. For this study, four different models of hearing protectors were tested: Bilsom 707 Impact II electronic earmuff, E·A·R Pod Express, E·A·R Combat Arms version 4, and the Etymotic Research, Inc. Electronic BlastPLG™ EB1. Study sample: Five samples of each protector were fitted on the fixture or inserted in the fixture's ear canal five times for each impulse level. Impulses were generated by a 0.223 caliber rifle. Results: The average IPILs increased with peak pressure and ranged between 20 and 38 dB. For some protectors, significant differences were observed across protector examples of the same model, and across insertions. Conclusions: The EPA's proposed methods provide consistent and reproducible results. The proposed impulse NRR rating should utilize the minimum and maximum protection percentiles as determined by the ANSI S12.42-2010 methods.

Key Words::

• Hearing protection devices
• impulse noise
• noise reduction rating
• noise-induced hearing loss

Acknowledgements

The authors acknowledge the contributions of NIOSH student interns Brian Kim and Joseph Echt for their assistance with the data analysis. The authors also acknowledge the contributions of the members of the Acoustical Society of America, Accredited Standards Committee S12 for Noise, Working Group 11 for their diligence in producing the ANSI S12.42-2010 standard. Portions of this work were supported by the U.S. EPA Interagency Agreement DW75921973-01-0.

Disclaimer: The views and the opinions expressed within this paper are those of the authors and do not represent any official policy of the Centers for Disease Control and Prevention and the National Institute for Occupational Safety and Health or the U.S. Environmental Protection Agency.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Note

1. 170 dB: 0.92m = 0.92x – 0.04y; 150 dB: 2.7m =1.5x – 2.2y; 130 dB: 19.2m =1.4x – 19.2y