when i designed cherry orchard at the atlantic’s stage two, an exchange i had with darron west prompted an experiment: use infrasonic frequencies (sounds whose tone falls below human threshold of hearing), building slowly in power over a long period of time, to cause unease in the audience; remove them suddenly for an untraceable feeling of relief. it’s a well-documented effect: a 2003 study in the uk paired 17hz tones with roughly half of the music in a concert and consistently found that, during those pieces that featured the infrasonics, people felt anxious, revolted, or afraid. but vic tandy is where it gets really interesting.

in the early 1980s, tandy designed medical machinery in a lab that his fellow employees swore was haunted. late one night, he felt it, too: the hair on the back of his neck prickled, he felt anxious, and he started to see a grey figure at the very corner of his vision. he soon noticed objects in his lab were vibrating of their own accord, and discovered that a large fan was the source; when he turned off the fan, the objects stopped shaking, and the room felt less oppressive. he theorised that the fan caused a low-frequency sound, and dug up some case studies that supported his notion that the feelings he and his coworkers had felt could be caused by infrasonic waves. among the material he pulled was one fascinating insight: the human eyeball has a resonant frequency (the frequency at which it needs the least amount of energy to vibrate – the frequency at which small amounts of sound cause big changes) of about 20hz. there is argument about the exact number in physics circles, and the article tandy published in the journal of the society for psychical research itself says 8hz<x<40hz, but he cites a nasa technical report that asserts 18hz as the eye’s resonant frequency. the fan’s 17hz standing wave, he thought, was making his eye physically change shape, blurring his vision and causing him to hallucinate a figure.

tandy already had an interest in ghosts, and became a bit of a paranormal investigator, arguing that infrasonics were responsible for many purported paranormal phenomena. but here’s the interesting thing, to me: infrasonics have many natural sources. waterfalls, waves; lightning; earthquakes, volcanoes; whales, elephants, even alligators. elephants drive subsonic frequencies into the ground, where they’re detected by other elephants hundreds of miles away using their feet. the notion that any of these, and other, as-yet unknown things, yield sound that can physically change things – whether the effect is as observable as the collapse of the tacoma narrows bridge, or as ephemeral as ghostly feelings – is largely underexplored, as far as i’m concerned. i would love to know more.