Some people love heavy metal music, while others can’t stand it. Either way, there is no denying that there is strategy and method to such singing. Krzysztof Izdebski is a doctor that works for the Pacific Voice and Speech Foundation, and he made it his mission to find out why phonotrauma, vocal cord bleeding and straining, occurs to some people, but not often heavy metal singers.

Dr. Izbeski used a high-speed camera designed to analyze vocal cords and record videos of throats in action. Through his research, Izdebski found that, when heavy metal singers sing, their vocal cords don’t touch one another. This is unlike typical screaming, but very similar to another occurrence: baby crying and screaming. Like babies, heavy metal singers aren’t damaging their vocal cords, as the instinct is to open the muscles in a way that air is pushed through the vocal cords.