Differential effects of suppressors on hazardous sound pressure levels generated by AR-15 rifles: Considerations for recreational shooters, law enforcement, and the military

Abstract

Objective: Firearm discharges produce hazardous levels of impulse noise that can lead to permanent hearing loss. In the present study, we evaluated the effects of suppression, ammunition, and barrel length on AR-15 rifles. Design: Sound levels were measured left/right of a user’s head, and 1-m left of the muzzle, per MIL-STD-1474-D, under both unsuppressed and suppressed conditions. Study sample: Nine commercially available AR-15 rifles and 14 suppressors were used. Results: Suppressors significantly decreased peak dB SPL at the 1-m location and the left ear location. However, under most rifle/ammunition conditions, levels remained above 140 dB peak SPL near a user’s right ear. In a subset of conditions, subsonic ammunition produced values near or below 140 dB peak SPL. Overall suppression ranged from 7–32 dB across conditions. Conclusions: These data indicate that (1) suppressors reduce discharge levels to 140 dB peak SPL or below in only a subset of AR-15 conditions, (2) shorter barrel length and use of muzzle brake devices can substantially increase exposure level for the user, and (3) there are significant left/right ear sound pressure differences under suppressed conditions as a function of the AR-15 direct impingement design that must be considered during sound measurements to fully evaluate overall efficacy.

Key Words:

• AR-15
• permanent hearing loss
• rifle fire
• suppressors
• silencers

Acknowledgements

Research reported in this publication was supported by the American Suppressor Association (ASA) through a contract to the University of Florida; the ASA also provided study weapons and ammunition for use at the Gainesville Target Range while testing suppressor devices. All manufacturers brought suppressors to the study site at their own expense and remained on site during testing to comply with federal firearm regulations. The content is solely the responsibility of the authors and does not necessarily represent the official views of the ASA, the manufacturers involved in testing, the University of Florida, the Alachua County’s Sherriff’s Department, the High Spring’s Police Department, or the Gainesville Target Range. The authors gratefully acknowledge equipment loans and technical support from Brüel & Kjær, especially Jim Wyatt, Gert Nyrup, and Alfonso Moreira. We also thank David Butcher of the Alachua County Sheriff’s Office for volunteering his time, and Mark Ocepek and Steve Bottcher from the Gainesville Target Range for donating their time, facilities, and suppressors to this study. All authors contributed to data collection. EL and CL collaborated in writing major portions of the manuscript and interpreting the data.

Declaration of interest

Edward Lobarinas, Christopher Spankovich, and Colleen G. Le Prell were employees of the University of Florida during the conduct of this study.