The US military buys a lot of foam ear plugs. Visit any base and you’ll find them under the bleachers at the firing range, in the bottoms of washing machines. They are cheap and effective at making noise less ... noisy.

But there’s a problem with earplugs on the battlefield. Soldiers won’t wear them. If they do wear them, they may miss other important (softer) noises happening around them. The result is lots of service members coming home from battle with tinnitus or hearing loss. In fact, for as long as the U.S. Department of Veterans Affairs has reported such statistics, tinnitus and hearing loss have remained the number one and two most common injuries of service members. Mary Roach, author of Grunt, has the story.