ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

3pNS3. Validating a mathematical model of noise hazard with varying numbers of rounds and peak pressures produced by a rifle.

G. Richard Price

Linda L. Pierson

Joel T. Kalb

Pam Mundis

Human Res. and Eng. Directorate, Army Res. Lab., Aberdeen Proving Ground, MD 21005

A mathematical model of noise hazard [G. R. Price and J. T. Kalb, 219--227 (1991)] has correlated very highly with hearing loss to 50 Friedlander impulses from two sources at 5 different peak pressures (135 to 145 dB). In order to extend the model's range four additional noise exposures were tested: two single impulse exposures (157- and 169-dB peak) and 6 or 12 impulses at 143-dB peak pressure. These specific conditions were also chosen to contrast the model's predictions with the ``CHABA'' damage risk criterion (DRC). Four groups of ten anesthetized cats were exposed to each condition and ABR thresholds at 1, 2, 4, 8, and 16 kHz were monitored to establish hearing loss immediately and 2 months later. In each case the model's predictions were upheld and rankings of hazard by the CHABA DRC were not. Furthermore, no simple linear frequency weighting would have predicted the losses. The model's hazard rating correlated well with the group hearing losses (coefficient near 0.8) and refinement of the model's annular ligament and the intracochlear hazard formula is expected to improve this correlation.