Toward a standard for assessing civilian firearm suppressor noise reduction: Environmental and procedural considerations

Currently, no consensus standard exists for measuring firearm suppressor noise reduction (FSNR). NATO developed a military standard to measure suppressor performance for an environment that does not generalize well to the recreational shooter. We propose a FSNR measurement standard using maximum accumulated A-weighted energy. Test environments included an outdoor space and a reverberant (indoor) facility with dimensions expected to provide similar results to the outdoor space. Two standard test barrels (0.308 and 0.223 caliber) mounted on a universal receiver system were used. For each environment and caliber, two ammunition types and three suppressors were tested, along with an unsuppressed condition. Ten discharges were recorded for each condition. Five field microphones were positioned at four locations around the universal receiver. Impulses in quasi-free field and reverberant environments are compared and the impact of combustion gases within the suppressor and the number of discharges to achieve stable estimates of noise reduction are considered. Similar FSNRs were observed in the environments. Clearing the suppressor of combustion gases had variable effects on impulse level, and relatively stable estimates of suppressor attenuation were achieved with seven test discharges.