Experimental study of shooting sound around semi-open shooting ranges

Measurements of shooting sound around semi-open shooting ranges are analyzed. Recorded sound signals show bullet sound and muzzle sound contributions. Time differences between bullet and muzzle sound pulses are explained by calculation of acoustical travel times. In general bullet sound contributions are stronger in forward directions (angles 0 to 90 degrees with respect to the shooting direction) than in backward directions. A representative frequency is defined to characterize the relative importance of bullet sound in the emitted sound spectrum. This is further analyzed by means of silencers on the firearms, as silencers suppress the muzzle sound but not the bullet sound. The effect of acoustical absorption material on the shooting range is also investigated. Differences of the order of 10 dB between different shooting ranges are attributed to acoustical absorption material of the overhead screens (baffles) on the range. For practical applications it would be useful to represent a shooting range by a single point source with a direction-dependent sound emission spectrum. The accuracy of this approximation is investigated.