Night Vision Acoustic Array (NVAA)

This report describes the concept and design of a handheld acoustic array developed for the Night Vision and Electronic Sensors Directorate the Night Vision Acoustic Array (NVAA) that keeps track of the location of sounds detected in a battlefield environment. The NVAAs purpose is to alert a forward observer (FO) of gunfire, explosions, and other transient signals outside of their field of view. The targets are displayed on the small screen relative to the array pointing direction. The FO slews the array in each detected direction to inspect the target with the scope mounted on top of the case. The technical specifications and design parameters are described, along with some caveats given the nature of acoustic propagation. The signal processing features a novel coherence detector, which uses simultaneously data from all channels, unlike the conventional approach of averaging pairs of them. The theory for this new coherence is described, along with an illustration of the performance improvement over the conventional approach. A users manual is also provided.