Seen At 11: 'Exploding Head Syndrome' Could Keep You Awake At Night

NEW YORK (CBSNewYork) -- There's nothing more frustrating than being awakened from a sound sleep, especially by a loud noise, but for millions of people the problem is all in their head.

Imagine being awakened from a sound sleep by an air-horn, a gunshot, or an explosion.

"It's very startling, and it is jarring," Neils Neilsen said.

As CBS2's Dick Brennan explained, it's even more jarring when you realize that the deafening sound is all in your head.

"I remember thinking that my head shocked itself," Neilsen said.

The sound of phantom symbols crashing together frequently startles Neilsen awake.

"It has crescendo effect quality to it, and sit stops abruptly," he explained.

Medical researchers estimated that as many as 20 percent of the world's population experiences what is known as 'Exploding Head Syndrome.' Which is defined as an imaginary sound or loud noise abruptly waking a person up.

"I've heard of cases where people have had it up to seven times a night, so you can imagine that would be very disruptive," Clinical Psychologist, Brian Sharpless said.

Sharpless recently conducted the largest study of its kind on Exploding Head Syndrome, or EHS as it is also known, for Washington State University.

"Even though we've known about EHS since the late 1980s, we still don't know a whole lot about it," he said.

Why EHS happens is still a mystery. One theory is that something like a hiccup, occurs in the part of the brain that controls hearing.

"So instead of shutting down your auditory neurons when you're going to sleep for some reason, they all fire at once and that's when you get this really loud noise," he said.

Spooked sleepers have taken to the internet to describe what it is like to live with this condition.

"Mine is like a whooshing sound, like a roaring whooshing sound," one sufferer said.

Sharpless said anyone can be a victim, but besides interrupted sleep he said there are no major health concerns.

"Exploding Head Syndrome is generally harmless in spite of the scary name," Sharpless said.