Developing a method to assess noise reduction of firearm suppressors for small-caliber weapons William J Murphy1, Adam R. Campbell1, Gregory A. Flamme2, Stephen M Tasko3, James E. Lankford4, Deanna K Meinke5, Donald S. Finan5, Edward L. Zechmann1, Michael Stewart6, 1Hearing
2
Loss Prevention Team, Division of Applied Research and Technology, National Institute for Occupational Safety and Health, 1090 Tusculum Ave. Cincinnati OH 45226-1998
Stephenson and Stephenson Consulting and Research, LLC, 2264 Heather Way, Forest Grove, OR 97116
[email protected] 3Western
Michigan University, Kalamazoo MI,
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4University 5University
of Northern Illinois, Dekalb IL,
[email protected]
of Northern Colorado, Greeley CO,
[email protected],
[email protected] 6Central Michigan
University, Mt. Pleasant MI,
[email protected]
Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the Centers for Disease Control and Prevention and the National Institute for Occupational Safety and Health. Products mentioned in this presentation are not endorsed by CDC/NIOSH Presentation to Acoustical Society of America, May 10, 2018
Firearm Exposures Military personnel
Law enforcement personnel
Recreational shooters
Ways to reduce firearm noise exposure? Hearing Protection Devices • Muffs/Plugs • Active/Passive
Reduces Noise at the Ear • Must have appropriate HPD for specific shooting activities • Must wear devices consistently • Research has shown that firearm users do not consistently use HPDs, even during target practice
How suppressors work • High level impulses are generated by sudden release of high pressure gases that accelerate the projectile • Pressure is reduced by coupling a chamber with larger volume to end of barrel • Baffles within the chamber act as a muffler • Suppressors cannot reduce the noise caused by supersonic flight of projectile
Elements of the gunshot noise
Settles, 2006
Experimental Setup for Microphones
Microphone Array
Firearms Tested • 300 Blackout • Daniels Defense SBR M4 • Glock 19 • Ruger 10-22 • Savage Arms 10 .223 • Sig Sauer MPXSA • Savage Arms 110 .338 LaPua
• Ambush A11 • DRD M762 • RockRiver Arms LAR-15 • Ruger American • Walther P22 • Kimber .45 ACP
Examples of peak level suppression
Examples of Reduction of LAeq by Suppressors
Comparison of Peak and LAeq Reductions
Frequency Spectrum of Suppressed/Unsuppressed Shot
Frequency Spectrum of Suppressed/Unsuppressed Shot
Frequency Spectrum of Suppressed/Unsuppressed Shot
Frequency Spectrum of Suppressed/Unsuppressed Shot
Spectrum of the Reduction by Angle: Low Velocity
Spectrum of the Reduction by Angle: High Velocity
The marginal effect of the suppressor by angle
Range of marginal effect of the all guns
Conclusions Angular Effects At the right or left ear • Peak levels were reduced between • Greater Marginal Effective Suppression to the sides 5 and 32 dB • LAeq levels were reduced between 6 • Must consider changing impulse and 28 dB levels with angle. In Front of Firing Line • Marginal effect for LAeq8 reduction was 10 to 20 dB across all guns Behind Firing Line • Marginal effect for LAeq8 reduction was 18 to 22 dB across all guns
Spectral Effects • N-wave affects suppression in the forward cone where N-wave is outside the blast wave. • N-wave affects high frequency suppression more. • Greatest suppression 0.4 to 1.0 kHz
Questions?
