Cited research
References
Why eyewear can undermine earmuff protection
Earmuffs are rated with a Noise Reduction Rating (NRR), a laboratory value measured without eyewear. In real-world use, the temples of safety, shooting, and prescription glasses pass between the head and the earmuff cushion, breaking the acoustic seal.
Research using gunfire found that sound reaching the ear was up to 17 dB louder when shooting glasses were worn under earmuffs. Other studies have found even greater losses: up to 18 dB with prescription glasses, and 15 to 25 dB of lost peak protection with certain earmuff and ballistic-glasses combinations. In some cases, the leak caused the earmuff to amplify low-frequency sound rather than reduce it.
The amount of protection lost varies with the earmuff and eyewear, and thicker temples generally cause larger losses. The studies below document this often-overlooked gap in hearing protection.
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Effect of shooting glasses on earmuff attenuation measured with an acoustic test fixture for gunfire impulsesView sourceOpen full article
Flamme, Murphy, Tasko, et al. (2024). Effect of shooting glasses on earmuff attenuation measured with an acoustic test fixture for gunfire impulses. Presented at the NHCA Annual Conference and the Acoustical Society of America meeting.
Researchers tested a top-selling earmuff and shooting-glasses combo kit, sold as a package to be worn together, using rifle fire and an acoustic test head. With the glasses on, the gunshot peak measured inside the earmuff was up to 17 dB louder than with the earmuff alone. The findings were also published in NHCA's Spectrum (August 2024) and in the Journal of the Acoustical Society of America. -
NIOSH Health Hazard Evaluation ReportView sourceOpen full article
Tubbs & Murphy (2003). NIOSH Health Hazard Evaluation Report HETA 2002-0131-2898, Fort Collins Police Services.
NIOSH measured police firearms on indoor and outdoor ranges with an acoustic mannequin. With safety glasses under the earmuffs, peak reduction was 12 to 18 dB, compared with 29 to 32 dB for the earmuffs alone. The leak from the glasses caused the earmuff to provide negative attenuation below 200 Hz, meaning low-frequency sound was actually amplified. -
Comparison of different types of hearing protection devices for use during weapons firing.View sourceOpen full article
This Canadian military study tested earmuffs with standard-issue ballistic glasses during weapons fire. Wearing the glasses cut peak protection by about 5 dB for one earmuff model and by 15 to 25 dB for another. The results show that how much protection is lost depends heavily on the specific earmuff and eyewear combination.
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Attenuation of earmuffs used simultaneously with safety spectacles in exposure to impulse noise.View sourceOpen full article
Researchers tested five earmuff models with three models of safety spectacles and with prescription glasses, using microphones placed in the ears of real people. Safety glasses with rectangular temples reduced impulse-noise protection by up to 9 dB, and prescription glasses reduced it by as much as 18 dB.
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Attenuation characteristics of fit-compromised earmuffs and various non-standard hearing protectors.View sourceOpen full article
This 3M laboratory study measured earmuff protection on human subjects wearing safety glasses, caps, hoods and other gear. An earmuff rated NRR 26 lost 2 dB with thin-temple safety glasses and 11 dB with thick-temple glasses.
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Selection of Earmuffs and Other Personal Protective Equipment Used in Combination.View sourceOpen full article
Researchers tested five earmuff models with two types of safety glasses on an acoustic test head. With the wider-temple glasses, sound levels under some earmuffs rose by more than 20 dB at 160 and 200 Hz, and the overall A-weighted level under the earmuffs rose by roughly 6 to 13 dB. The authors recommend choosing safety glasses with thin temples when they must be worn with earmuffs.
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The effect on earmuff attenuation of other safety gear worn in combination.View sourceOpen full article
Seventy-two participants were tested wearing hard-hat-mounted earmuffs alone and in combination with safety glasses, a half-mask respirator, or both. Protection dropped by as much as 5 dB with glasses or the respirator, and by 9 dB with both.