The sounds of nails on a chalkboard, the sound of someone vomiting, the sound of a baby screaming – all pretty unpleasant sounds. But not so unpleasant that you might die. But could a sound kill you?
Well, maybe, but it won’t be the kind of sound that you hear. Instead, it would be a sound you feel. Popular Science excerpts the book The Universal Sense: How Hearing Shapes the Mind:
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.
But, before you get too excited (or maybe scared) about the prospect of a sound weapon, it might actually be really hard to use sound to kill anybody. Different parts of your body resonate at different frequencies. So let’s say you pick the frequency that the skull vibrates. Well the skull isn’t’ just the skull, it’s packed in with soft, squishy stuff like brains and skin and connective tissue and blood. Those things will all suck up the resonant frequencies before any real damage can happen. You’d need something extremely loud and close to the head to do any real damage beyond a headache.
Now there are sonic weapons out there, they’re just not lethal. Take this one, from Poland, for use again Euro 2012 fans.
So while it might not explode heads, sound could keep rowdy soccer hooligans at bay.
More from Smithsonian.com: