In her article “The Loudest Sound In The World Would Kill You On The Spot,” science writer Maggie Koerth-Baker describes the frightening power of extremely low-frequency soundwaves (infrasounds):
“Humans exposed to infrasounds above 110 decibels experience changes in their blood pressure and respiratory rates. They get dizzy and have trouble maintaining their balance. In 1965, an Air Force experiment found that humans exposed to infrasound in the range of 151-153 decibels for 90 seconds began to feel their chests moving without their control. At a high enough decibel, the atmospheric pressure changes of infrasound can inflate and deflate lungs, effectively serving as a means of artificial respiration.
But at least humans are spared from hearing such massively loud infrasounds. Koerth-Baker quotes soundwave researcher Milton Garces on how humans evolved a way to cope with infrasounds that are pervasive as natural background noise (though thankfully not lethally loud). Such infrasounds include microbaroms from marine storms and the sound of wind: “We developed our hearing threshold so we don’t go nuts. If we had hearing perception in that band it would be difficult to communicate. It’s always there.”