### 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.