Noise exposure profiles for small-caliber firearms from 1.5 to 6 meters

Small caliber firearms (rifles, pistols and shotguns) are commonly used at outdoor firing ranges for training in shooting skills, job qualification and for recreation. Firearm noise from fifty-four weapons was measured at an outdoor range in the near field (6 meters and closer) of the weapons using a radial array of 18 microphones centered on the shooter’s head. Each weapon was fired five times and the microphone array was sampled at 200 kHz with at least 16-bit resolution. Peak sound pressure levels and damage risk criteria (e.g. MIL-STD 1474D, 8-hour Equivalent A-weighted Level (LAeq8), and Auditory Hazard Assessment Algorithm for Humans (AHAAH)) were computed for each microphone and compared across weapon type, caliber and load. The acoustic propagation from the muzzle to the microphone was modeled using a simple image source over a reflecting plane. The impedance of the ground was estimated from the observed data and was used to compare the measured waveforms with the estimated waveforms. These data will be used to model the exposures for multiple shooters and observers standing at or behind the firing line.