Blast Overpressure Studies. Nonauditory Damage Risk Assessment for Simulated Muzzle Blast from a l2Omm Ml2l Mortar System.

Abstract : This study was undertaken to establish the subthreshold, threshold, and suprathresholds for nonauditory injuries in a simulated muzzle blast environment like that produced when firing a 120mm M121 mortar system. A vertical axis explosively driven shock tube, in combination with reflector shields, was used to produce the required muzzle blast pressure-time pattern. Varying numbers of anesthetized sheep were subjected to 6 or 50 blasts of simulated muzzle blast waves in 1.5- to 3.0-dB increments. The results of the study demonstrated that sheep could be exposed to Pmax levels consisting of 6 blasts of 36 kPa each and 50 blasts of 30 kPa each and sustain no injuries to trivial upper respiratory tract injuries at most. Threshold injuries were calculated to occur at 53 and 34 kPa for 6- and 50-blast exposures, respectively. Suprathresholds for URT and GI tract lesions were predicted to be 69 and 46 kPa for 6 and 50 blasts each. A suprathreshold for lung hemorrhage was predicted at 277 kPa for 6 exposures. Comparative analyses of this study with previous complex wave studies demonstrated that the safe nonauditory subthreshold for as many as 100 complex blastwave exposures was 22 kPa.