Have you ever wondered why heavy metal singers can scream for hours on end, but other singers lose their voices all the time? You’d think it would be the other way around, right? It’s a great medical mystery of music that, until recently, had no solution in sight. But recent research by a San Francisco doctor may hold the secret: heavy metal singers’ vocal chords behave the same way a baby’s does.

Krzysztof Izdebski of the Pacific Voice and Speech Foundation has been interested in heavy metal singers for years. But it’s not because he’s a metal head! He often works with people who have voice problems, and wants to find a solution for them. Most of the time vocal injuries are due to physical trauma (like getting hit in the throat) or from repetitive straining – like actors, teachers, and singers trying to speak too loudly for too long. Usually vocal chords just start to bleed and shut down after straining – a malady called phonotrauma – and can take several months to heal.

Yet phonotrauma never seems to happen to heavy metal singers, so Izdebski took to finding out why. The doctor used a special high speed imaging camera specifically designed for vocal chord work to analyze a heavy metal singers’ growling. It can record video of throats working at 16,000 frames a second, and has special software that lets it digitally recreate vocal structures. Izdebski’s camera caught something very interesting: when a heavy metal singer growls, their vocal chords don’t actually touch each other. Unlike a regular person’s screaming, air is simply pushed through the chords and ‘rattles’ them to make sounds – exactly the same way a baby’s vocal chords work.

The crying, screaming, and growling of a baby rarely damages their vocal chords because they instinctively can ‘open’ those muscles in the same way a heavy metal singer does. Unfortunately that ability is forgotten as babies grow older, and the technique can be very difficult to teach – especially to patients struggling with vocal issues. But for whatever reason, heavy metal singers are able to utilize the same method – and because of it, growling and screaming night after night does little to no damage to their chatter boxes.

Izdebski hopes that more research into the methods of metal singers will be useful for his vocal patients as well. If metal singers can open their chords intuitively, the doctor believes the same thing can eventually be taught to those who have damaged them. Crushed larynx injuries are specifically his target – they’re impossible to repair, and most patients lose their voices forever. But maybe some guttural screaming could help some of those people get bits of their voices back. And if metal singers can learn to do what babies do instinctively, hopefully anybody can!

For more detailed information on Dr. Izdebski’s studies, including a clip of some heavy metal vocal chords in action, check out the video by Inside Science below: