The United States Marine Corps buys a lot of earplugs. You find them all around Camp Pendleton: under the bleachers at the firing range, in the bottoms of washing machines. They are effective, and cheap as bullets,which also turn up in the washing machines. (And, though you didn’t ask for it, here’s one more similarity between bullets and earplugs: Both have been used by physicians to protect their ears from screams. The Army Medical Department Journal states that the real reason soldiers in the pre-anesthesia era were given a bullet to bite was not to help them endure the pain but to quiet their screams. And from a paper called “The History and Development of the E-A-R Foam Earplug” we learn that emergency room docs use foamies “to block the screams of children during difficult procedures.” This was part of a section on “unusual applications,” none of which were especially unusual. I may have had unreasonable expectations for the history of the foam earplug.)
For decades, earplugs and other passive hearing protection have been the main ammunition of military hearing conservation programs. There are those who would like this to change, who believe that the cost can be a great deal higher. That an earplug can be as lethal as a bullet.
Most earplugs reduce noise by 30-some decibels. This is helpful with a steady, grinding background din—a Bradley Fighting Vehicle clattering over asphalt (130 decibels), or the thrum of a Black Hawk helicopter (106 decibels). Thirty decibels is more significant than it sounds. Every 3-decibel increase in a loud noise cuts in half the amount of time one can be exposed without risking hearing damage. An unprotected human ear can spend eight hours a day exposed to 85 decibels (freeway noise, crowded restaurant) without incurring a hearing loss. At 115 decibels (chainsaw, mosh pit), safe exposure time falls to half a minute. The 187-decibel boom of an AT4 anti-tank weapon lasts a second, but even that ultrabrief exposure would, to an unprotected ear, mean a permanent downtick in hearing.
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Image courtesy of aetc.af.mil