LTC Lorraine Babeu, Mary Ginseel, M.S., MSG Lamar Garrett, Tomasz Letowski, Ph.D.
Level dependent hearing protection provides little to no attenuation when the noise levels are low; however, when impulse noise such as weapons fire is present and the attenuation mechanisms of the protector are activated, level dependent hearing protection is key to a safe listening environment. This type of hearing protection is well suited for dismounted troop movement and field artillery. Within the last ten years there has been great interest in level dependent earmuffs and earplugs starting with the system developed at the French-German Institute and in use by the French Army. The American version, the combat earplug, has two sides. The yellow side is the level-dependent side and the green side is a standard earplug. Twelve soldiers received pre and post audiogram and distortion product otoacoustic emission (DPOAE) testing after firing the M16 or M4 semi-automatic rifle. During firing they wore either the French or American version of the combat arms earplug. The goal was to determine if there was a change in the audiogram or the DPOAE as result of the exposure to weapons fire.