There’s an elevator in the Brown University Biomed building (hopefully fixed by now) that I’ve heard called “the elevator to hell,” not because of destination but because there is a bent blade in the overhead fan. The elevator is typical of older models, a box 2 meters by 2 meters by 3 meters with requisite buzzing fluorescent, making it a perfect resonator for low-frequency sounds. As soon as the doors close, you don’t really hear anything different, but you can feel your ears (and body, if you’re not wearing a coat) pulsing about four times per second. Even going only two floors can leave you pretty nauseated. The fan isn’t particularly powerful, but the damage to one of the blades just happens to change the air flow at a rate that is matched by the dimensions of the car. This is the basis of what is called vibroacoustic syndrome—the effect of infrasonic output not on your hearing but on the various fluid-filled parts of your body.
People don’t usually think of infrasound as sound at all. You can hear very low-frequency sounds at levels above 88–100 dB down to a few cycles per second, but you can’t get any tonal information out of it below about 20Hz—it mostly just feels like beating pressure waves. And like any other sound, if presented at levels above 140 dB, it is going to cause pain. But the primary effects of infrasound are not on your ears but on the rest of your body.
Because infrasound can affect people’s whole bodies, it has been under serious investigation by military and research organizations since the 1950s, largely the Navy and NASA, to figure out the effects of low-frequency vibration on people stuck on large, noisy ships with huge throbbing motors or on top of rockets launching into space. As with seemingly any bit of military research, it is the subject of speculation and devious rumors. Among the most infamous developers of infrasonic weapons was a Russian-born French researcher named Vladimir Gavreau. According to popular media at the time (and far too many current under-fact-checked web pages), Gavreau started to investigate reports of nausea in his lab that supposedly disappeared once a ventilator fan was disabled. He then launched into a series of experiments on the effects of infrasound on human subjects, with results (as reported in the press) ranging from subjects needing to be saved in the nick of time from an infrasonic “envelope of death” that damaged their internal organs to people having their organs “converted to jelly” by exposure to an infrasonic whistle.