Have you ever been drifting off to sleep when suddenly you hear what sounds like a gunshot, a door slamming, or an explosion inside your head? You jolt awake, heart pounding, sit upright in bed, but ...

Add Yahoo as a preferred source to see more of our stories on Google. Have you ever been drifting off to sleep when suddenly you hear what sounds like a gunshot, a door slamming, or an explosion ...