Blast Overpressure Studies with Animals and Man: Task Order 1: Firing from aBunker Simulator Study, Task Order 4: Nonlinear Plug Study

摘要

To satisfy the Army's need for realistic safe limits for heavy weapon noise whilewearing hearing protection, a 2-1/2 year study was undertaken. Using active duty military volunteers, 64 subjects established that the auditory system could be adequately protected with the RACAL(registered) muff from one to three exposures of the reverberant waveforms obtained from a rocket launcher out of an enclosure. Thus, nonauditory considerations set the exposure limits for this type of waveform. This research was accomplished under Task Order 1. Using 27 subjects, two types of nonlinear (increasing attenuation with level) plugs type of hearing protection were evaluated using 6 to 100 exposures of a freefield waveform of 1.5-ms duration. With the limited number of subjects, neither plug was proven adequate to protect the auditory system from this type of waveform. Several subjects had a temporary threshold shift (TTS) of their hearing of more than 25 dB. The compressible foam plug, did appear to provide adequate protection up the auditory limits for this waveform. This research was accomplished under Task Order 4.