Numerical simulation of sound emission from weapons

Noise level near military firing ranges must be carefully controlled. To achieve this, one often employs a linear noise propagation model to calculate the noise exposure in the adjacent area. Input for such propagation models are noise levels near the source, usually measured with a microphone. However, it is very expensive to perform measurements for every new weapon under all types of use. This has motivated us to numerically predict the noise levels that serve as input for linear noise propagation models. In this paper, we use numerical simulations to calculate the propagation of the pressure wave close to the muzzle of a weapon. The acceleration of the projectile and the distribution of pressure inside the barrel are calculated using the code IBHVG2 (Interior Ballistic of High Velocity Guns). The end state, calculated by IBHVG2 as the projectile leaves the muzzle, is then used as the initial state for the hydrocode AUTODYN to determine the propagation of the shock wave. The calculated pressure is compared with experimental measurements for an AG3 rifle at a distance of 80 cm from the barrel, and the results correspond well. The method described here applies to weapons of all sizes, from hand guns to artillery guns. The end state of the combined IBHVG2/AUTODYN simulation can be used as input for another code to calculate propagation over a larger distance. The method can also be applied to situations where the blast wave close to a weapon is of interest, e.g. to calculate strain on personnel firing a cannon or effects of firing weapons in confined spaces.