ASA 125th Meeting Ottawa 1993 May

5aNS7. Effects of high-intensity impulse noise on the hearing of humans wearing hearing protection.

James H. Patterson, Jr.

US Army Aeromed. Res. Lab., P.O. Box 577, Fort Rucker, AL 36362-5292

Daniel L. Johnson

EG & G Special Projects, Albuquerque, NM 87119-9024

Current exposure limits for high-intensity impulse noise are based on very limited amounts of data. This study was undertaken to provide new data on the effects of a variety of impulse noises on humans exposed while wearing hearing protection. The impulses used in this study were produced by detonation of explosive material. Two types of impulses were used. One had an A duration of approximately 3.0 ms, while the other had an A duration of approximately 0.8 ms. Exposures were presented at one impulse per minute. The results of the long duration impulse have been presented previously. This presentation focuses on the short duration impulse. Sixty-five volunteers were exposed on successive days to six impulses with intensities ranging from 178 to 196 dB SPL for the shorter impulse. The number of impulses then was increased from 6 to 100 at the tolerable level. The results indicate that minimal hearing protection is adequate for 6 of the 0.8 impulses up to 196 dB SPL. It was inadequate for 12 or more impulses at 193 or for 50 or more impulses at 190 dB SPL. Protection is adequate for 50 impulses at 187. Hearing protectors which provide more attenuation were adequate for all conditions used in this study.