Exploding head syndrome (EHS) is classified as a sleep disorder or headache disorder. It occurs when someone falls asleep or wakes up to loud auditory hallucinations. These noises may sound like explosions or thunder and do not tend to last long, but they can still be frightening and may make it harder to sleep. There is typically no pain associated with EHS, and it doesn't lead to other conditions, so it is considered harmless. While in general EHS is a rare occurrence, some people hear the loud noises multiple times a night. Other symptoms of EHS include seeing a flash of light, feeling a tingling sensation run through the body, or suddenly feeling hot.