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When troops return from war, they suffer from all sorts of invisible injuries. One of the big ones is hearing loss. The Defense Department says more than half of all troops returning from Iraq or Afghanistan suffer from some sort of damage to their hearing. As part of his series Joe's Big Idea, NPR's Joe Palca has been exploring new solutions to old problems. And today he's looking at how the Army is trying to protect soldiers from hearing loss.
JOE PALCA, BYLINE: Loud sounds cause problems, whether it's a rock concert or a jackhammer or a gunshot.
KRISTEN CASTO: Your ears can't handle loud sounds without suffering mechanical damage to the inner ear that results in permanent hearing loss.
PALCA: Lieutenant Colonel Kristen Casto is an audiologist and consultant to the Army Surgeon General. She says there are many ways to protect your ears when you are exposed to loud sounds. Sticking a piece of expandable foam in your ears does a pretty good job.
CASTO: But when you need to maintain auditory awareness, that's not the proper hearing protector.
PALCA: Maintaining auditory awareness means being able to hear potentially important quiet sounds, like a door opening or a twig breaking, even when there are guns or explosions going off nearby. Casto says what fighters needed was a kind of smart ear plug, one that could boost sounds like a door opening or a twig breaking.
CASTO: But then reduces the intensity of high-level impulse noises so you're protected from that noise.
PALCA: So the Army has come up with something it calls TCAPS, the tactical communication and protective system.
DOUG BRUNGART: The technology is not really that complicated.
PALCA: Doug Brungart is chief scientist at the Audiology and Speech Pathology Center at the Walter Reed National Military Medical Center.
BRUNGART: So you can think about it, it's just an adjustable volume knob that the louder the sound outside gets the more it turns down the volume so the person wearing the device can still hear the sound. But it's never going to get so loud that it's going to be damaging.
PALCA: The TCAPS device looks pretty much like a pair of earbuds with some built-in electronics. It's actually a little bit hard to demonstrate how TCAPS works on the radio, but here's a recording the Army sent me of how TCAPS would reduce the sound of a gunshot. This is the sound of an M4 rifle being fired without TCAPS.
(SOUNDBITE OF GUNSHOT)
PALCA: And here it is with TCAPS protection.
(SOUNDBITE OF GUNSHOT)
PALCA: Trust me, in real life, one is much softer than the other. Lieutenant Colonel Casto says about 20,000 TCAPS devices have been deployed in the field. She says using the device changes the way you hear the world and takes some getting used to.
CASTO: So that's why we are very careful when we issue the devices that we train the users on how to use them and we allow them time to adapt to them.
PALCA: Although the Pentagon knows how many TCAPS devices have been deployed, it's trickier to know whether troops are always using them in the field. Doug Brungart says troops can be wary of anything that could limit their hearing on the battlefield.
BRUNGART: We really need them to feel like they are still able to maintain their awareness. And the more we advance this technology that's really what we're focused on, this idea of transparency, that somebody wearing the protector feels like they'll hear everything they need to hear.
PALCA: Brungart is confident that's the case with TCAPS. And he's certain using the system will mean fewer veterans in the future with permanent hearing problems. Joe Palca, NPR News.