Evaluation of hearing protection devices with high-amplitude impulse noise

Abstract

Presently, the evaluation of HPDs (hearing protection devices) is mainly based on audiometric threshold methods. However, in the military environment soldiers may be exposed to impulse noise levels of 190 dB and higher if large caliber weapons or IEDs (improvised explosive devices) are considered. In this case it seems reasonable to expect that an evaluation done at hearing threshold might not represent the protection which will be encountered at these highest levels. Therefore, it is necessary to evaluate the HPDs with signals close to the effective exposure. ISL has developed procedures using explosive charges creating very high levels of impulse noise (up to 195 dB peak) for the evaluation of HPDs. ISL also has developed an artificial head that can withstand this type of exposure and has sufficient self-insertion loss for the measurement of double hearing protection. The presentation will give a description of the techniques used at the ISL. It will present some results showing the possibilities to determine the performance of different types of HPDs when subjected to extreme impulse noise levels. Moreover, the new version of the ISL artificial head, compatible ANSI-ASA-S12.42-2010, and possible problems when using it will be presented.