Infrasound signature measurements for U.S. Army infantry weapons during training

Abstract

United States Military personnel are exposed to blast overpressure from a variety of sources during training and military operations. While it is known that repeated exposure to high-level blast overpressure may result in concussion like symptoms, the effect of repeated exposure to low-level blast overpressure is not well understood yet. Impulsive acoustic sources such as pressure waves generated by explosions, artillery launches, and rocket launches are typically characterized by a broadband energy distribution with resulting pressure measurements that exhibit frequency components well into the infrasound range. This study focused on data acquired in the audible and infrasound range during infantry weapons training for machine gun, grenade launcher and rocket fire events. Time, frequency and time-frequency analysis are used to quantify infrasound intensity for each event type. High resolution time-frequency analysis using the synchrosqueezed wavelet transform is used to precisely quantify energy content in the lowest frequency range. Preliminary results indicate that data collected from these weapon systems exhibited a large amount of infrasound in the range between 2 and 20 Hz. This energy can couple directly with the human body and in case of repeated exposures this coupling can include altering of physiological processes.