Distributed acoustic sensing of shots in realistic environments

Abstract

Upon firing, most weapons emit very loud sounds. These sounds propagate over the battlefield and are distorted by the atmospheric effects, absorbed by the ground, reflected on or diffracted around buildings or mountains. It is of obvious operational interest to develop sensing systems to localize these sound sources, with arrays of distributed sensors. This study develops an original sensing approach. It uses the time-matching method, based on finding the best match between pre-calculated times of arrivals (TOAs) of the shot sounds and measured TOAs from a set of synchronous, distributed sensors. Predicting the TOAs requires a physical model able to factor in the impact of complex 3-D environments (wind and sound speed gradients, obstacles), and of complex sound sources (e.g., combination of muzzle blast and supersonic projectile wave). A very fast interface-tracking model is used, based on Sethian's Fast-Marching method, for pre-calculating the TOAs in a general and comprehensive framework. Applications to localization of shots in urban environments and to localization of long range artillery gun are presented. They demonstrate that, compared to standard methods, the above matching-and-marching approach can work without classification, with less sensors, or with a much smaller baseline array.