Firearm Owners United | Daniel Kuhl | A breakdown of firearm sound suppressing devices
The need to moderate sound
The activity of shooting firearms is one that is enjoyed by many Australians, with Australia having over 800,000 individually licenced firearm owners (1). Whilst shooting is a fun, highly enjoyable, and generally safe sport, it is not without inherent dangers. These dangers come from the sound produced from the firearm, which range from ~140 decibels to ~170+ decibels, which is comparable to a jet engine or rocket lift off happening right next to your ear (2) (3). This is undesirable as it has painful and long-lasting consequences, namely hearing damage, and for a detailed breakdown read a previous Firearm Owners United article here. With the consequences being so dire, there is a clear need to protect shooters hearing. Part of the solution is achieved by using Personal Protective Equipment (PPE) designed to mitigate damage from loud noises called Hearing Protective Devices (HPDs), however these are not always the full solution. Two popular products for ear protection, SureFire Ep4 Sonic Defenders (inner ear protection) and Howard Leight Impact Sport Earmuffs (outer ear protection) both have a Noise Reduction Rating (NRR) of 24 decibels. Combining the two types of hearing protection, inner and outer ear, is extremely helpful and recommended, however the stacking of the two does not mean 48 decibels of protection (4). The stacking of the two types of hearing protection is estimated to provide an additional 5 decibels of protection to the highest rated NRR piece of PPE that is being applied (5) (6). This means that the stacking of hearing protection will only provide an estimated 29 decibels of protection, leaving the user still being exposed to over 100 decibels every shot, well above the safe limit. Following the Workplace Health and Safety rules for the hierarchy of control for risks in the workplace, two steps before PPE should be engineering (7).
The engineering solution: Suppressors
A firearm suppressor, silencer, sound moderator, can, muzzle, are all interchangeable terms for the same thing: a device that is attached to the muzzle of a firearm that will modulate the speed and pressure of the burning propellant pushing the bullet and lowering the overall sound of the blast produced. Generally, they will be made from steel or titanium, cylindrical in shape, and hollowed out with bored baffles to allow the projectile to pass through. As the burning gas passes the baffles, it is slowed down, which then reduces the produced sound (8).
Effectiveness of suppressors & dispelling myths
Suppressors are a fantastic tool for reducing sound levels produced by shooting, however they are generally portrayed incorrectly – commonly by reducing the sound to almost nothing. The effectiveness of a suppressor relies on several factors, these include build quality, design quality, materials, the calibre being shot, and the velocity of the ammunition. Commercially, shooters can buy ammunition that ranges from sub-sonic to super-sonic velocity, sub-sonic ammunition is designed to shoot the projectile at a velocity lower than the speed of sound while super-sonic ammunition is designed to shoot the projectile at a velocity above the speed of sound. Across multiple conditions, with multiple variables (including different ammunition brands and firearms), one study on the use of a suppressor on AR-15’s (a .223rem calibre) noted a noise reduction range of 7-32 decibels, and always above 140 decibels with the only exception when sub-sonic ammunition was used (9). This means that even with a suppressor attached, the firearms all produced sounds that are above the safe limit. A study done with sub-sonic ammunition and suppressors showed that the decibel level reduction at the shooters ear was between 17 and 24 decibels, however, does not show the overall result, they do conclude that the cumulative exposure at these levels do produce a significant risk (10). A study done in controlled conditions shooting 9mm and 45 ACP pistols, 223rem and 308win rifles, was conducted and reduced the sound by a significant, however still loud, amount. The 9mm sound was reduced from ~159 decibels to ~128, the 45 ACP from ~160 decibels to ~130 and when wet (as it was designed to work wet) to 121 decibels. The 223rem rifle sound was reduced from ~160 decibels to ~135, and the 308win from ~160 decibels to ~135 (11). These numbers are significant and absolutely will help mitigate hearing damage to a shooter’s ear, however clearly suppressors do not reduce the sound to nothing, in fact many shots are still quite loud.
The sound solution conclusion
Neither suppressors alone nor HPD’s provide complete protection for a person using firearms or being near firearms in use. A combination of inner and outer HPDs with a suppressor attached to the firearm would significantly contribute to mitigating damage to a shooter’s hearing and would be an ideal situation. A suppressor does not reduce the noise generated by a firearm to such a low amount it is inaudible, the reality is that the sound produced remains quite loud, and as such does not pose a threat to public safety. Australian shooters being given the option to purchase and use suppressors would result in a safer community with less hearing problems.
- Alpers, Philip and Picard, Michael. Australia: Number of Licensed Firearm Owners. GunPolicy. [Online] 15 November 2020. https://www.gunpolicy.org/firearms/compareyears/10/number_of_licensed_firearm_owners.
- Prevention of Noise-Induced Hearing Loss from Recreational Firearms. Meinke, Deanna K, et al. 38, November 2017, Seminars in hearing, Vol. 4, pp. 267-281.
- Safe Work Australia. Noise. Safe Work Australian. [Online] [Cited: 07 January 2021.] https://www.safeworkaustralia.gov.au/noise.
- Clason, Debbie. Shooter’s ear: Hearing loss caused by gunfire. Healthy Hearing. 21 October 2019.
- The combined sound attenuation of earplugs and earmuffs. Abel, Sharon M and Armstrong, Nadine M. 1, 6 November 1992, Applied Acoustics, Vol. 36, pp. 19-30.
- Berger, Elliott H. Extra Protection: Wearing Earmuffs and Earplugs in Combination. Audiology Online. [Online] 6 August 2001. [Cited: 07 January 2021.] https://www.audiologyonline.com/articles/extra-protection-wearing-earmuffs-and-1218.
- Victorian Government. The hierarchy of control. WorkSafe Victoria. [Online] 25 February 2020. [Cited: 07 January 2021.] https://www.worksafe.vic.gov.au/hierarchy-control.
- United States Department of Alcohol, Tobacco, and Firearms. Firearms – Guides – Importation & Verification of Firearms – Gun Control Act Definition – Silencer. Alcohol, Tobacco, and Firearms. [Online] 26 April 2018. [Cited: 07 January 2021.] https://www.atf.gov/firearms/firearms-guides-importation-verification-firearms-gun-control-act-definition-silencer.
- Differential effects of suppressors on hazardous sound pressure levels generated by AR-15 rifles: Considerations for recreational shooters, law enforcement, and the military. Lobarinas, Edward, et al. 1, 28 January 2016, International Journal of Audiology, Vol. 55, pp. S59-S71.
- The reduction of gunshot noise and auditory risk through the use of firearm suppressors and low-velocity ammunition. Murphy, William, et al. 1, February 2018, International Journal of Audiology, Vol. 57, pp. 28-41.
- Comparison of Muzzle Suppression and Ear-Level Hearing Protection in Firearm Use. Branch, Matthew Parker. 6, 24 February 2011, Otolaryngology–Head and Neck Surgery, Vol. 144, pp. 950-953.