US Army's smart earplugs spare soldiers from loud noises
 

As you might imagine, soldiers can't just use garden variety earplugs to protect their ears. It might tone down the sounds of explosions and gunshots, but it'll also prevent them from hearing a crucial command or an enemy on the other side of a door...

http://www.engadget.com/2016/06/05/u...smart-earplug/