YOU’D THINK IT would be the sounds you can hear — ghoulish groaning, unexplained thumps and taps — that scare you, even make you believe in ghosts. But maybe it’s not. This, at least, is the tantalizing possibility when I descend, with a clutch of other reporters, to the basement swimming pool of London’s Hilton Bankside Hotel, a swank, newish building just south of the River Thames. We are there to experience something weird. And it’s all supposed to come down to a sound that we can feel, but not hear.
The event, suggestively titled the “Voice of God,” is a project of Bompas & Parr, a London-based events design group, and is part of the Southwark Merge arts festival. After we sign away our right to complain if anything unpleasant happens, our cheerful host, Sam Bompas, leads us on an awkward elevator ride down to the lowest level basement. Here, we watch a preparatory video, three minutes of bright lights and explosions, plus an explanatory voice-over. Then we are invited to do an “eyeball cleansing” exercise — tracing figure-eights over our closed eyelids with our fingers — escorted through the empty women’s changing room, asked to remove our shoes, and released into the humid air of the pool room.
Looming over the far end of the pool is a set of massive speakers, eight of them, painted gold, stacked atop a black subwoofer nearly 6 feet wide, 3 feet tall, and 3 feet deep.
“This is the sweet spot here,” says Bompas, standing at the edge of the pool. I sit there, toes in the warm water, and the team fires up the speakers.
The experience lasts five minutes. It’s loud. Muffled explosions reverberate through my chest cavity. Strobe lights mimic the effect of artillery or fireworks. The sound morphs with the lights, giving way to what sounds like dance music; this could be a rave in an underground swimming pool during an air raid. Then indistinct voices overlay the beat, as if trying to have a phone conversation at a rave in a swimming pool during an air raid. And that was just the part I could hear.
It all ends abruptly, the sudden absence of noise a shock. No one speaks. But Bompas wants to know: Did anyone hear the voice of God? See an apparition? No one did — but a number of people did feel strange. Some reported tingling and anxiety; one developed a tic in his lip that disappeared after the experience stopped; another reported a metallic taste in his mouth. Had the experience gone any longer, maybe we would have seen a ghost.
. . .
THE PURPOSE OF the event was to exploit one of the weirder things about being human: our susceptibility to what’s called “infrasound.” Sound, generally speaking, is an air event that produces a wave; frequencies audible to humans are usually between about 20 Hz to about 20,000 Hz. Low frequency sound, below 20 Hz, is infrasound. In theory, these low frequencies resonate not with our ears, but with our bodies. Infrasound can activate our sympathetic nervous system, which regulates things like skin temperature, blood pressure, and heart rate, or resonate with our eyeballs to produce visual disruptions — a “smearing,” weird lights, and afterimages, kind of like the splotches of color produced when you press your fingers to your closed eyes. Depending on how you and your cultural context interpret odd experiences, it can make you see ghosts or aliens or psychedelic lights, feel as if you’ve been touched by the divine, or just a bit unsettled.
The link between infrasound and anomalous experiences first emerged in a 1998 paper published by Vic Tandy and Tony Lawrence in the Journal for the Society of Psychical Research. Tandy, then a design engineer at a medical equipment manufacturer, had been warned that the lab he was working in was haunted — people reported feeling presences and cold spots, seeing movement in the corners of their eyes. A scientist and a skeptic, he had largely dismissed the claims.
But one night, Tandy was working late. He felt cold, but was sweating; the lab and factory were deserted, but he couldn’t shake the feeling that he wasn’t alone. He walked through the lab, checking the caps on bottles of noxious chemicals to make sure there were no leaks, then sat down at his desk with a cup of coffee. And then he saw it. An indistinct gray shape sidled into the left periphery of his vision. It moved, he said, like a person would, but it disappeared when he turned to face it. “It would not be unreasonable to suggest I was terrified,” Tandy wrote later. He packed up and went home, thinking that maybe he was “cracking up.” The next day, Tandy came back to work and brought his fencing foil (surprisingly, not for self-defense). A keen amateur fencer, he needed to use the lab vise to hold the foil while he worked on the handle. But while the foil was in the vise, it began to vibrate wildly.
Things started to make sense.
Tandy suspected that the vibration might be due to an inaudible low-frequency sound wave rolling between the walls of the room. Using the blade in the vise as a measure, Tandy determined that the wave was about 19 Hz. Sleuthing around, he learned that a new extractor fan had been installed in the janitorial closet at the end of the room. When the fan was switched off, the wave disappeared. So did the weird symptoms, the feelings of unease, the strange visual disruptions. Tandy went to the literature. Other researchers had found that infrasound at levels at or below 19 Hz had strange effects on humans; one experiment found that 12 Hz broadcast at only around 85 decibels could cause “sudden and violent nausea.” Tandy had found his ghost.
In May 2003, University of Hertfordshire psychologist Richard Wiseman decided to test Tandy’s theory. Teaming up with one of his graduate students, two National Physical Laboratory acousticians and soundscape composer, and engineer Sarah Angliss, Wiseman put on two concerts in London. During both concerts, participants were asked to give written feedback about their emotional states at four specific points in the show. In one of the concerts, however, a 7-foot sewer pipe outfitted with a subwoofer that produced safe levels of infrasound was switched on at two of those key points. Wiseman found that the audience subjected to infrasound “reported significantly more strange experiences” than the control audience, he wrote in his 2007 book, “Quirkology.” These experiences included increased heart rate, anxiety, fluttering in the stomach, shivering, and, in one woman’s notable case, “pre-orgasmic tension in body and arms, but not in legs.”
I did not experience any of that at “Voice of God.” I found the combination of sound, light, and place to be a bit discomfiting, but whether the infrasound caused that I can’t say. Researchers question the biophysical mechanism by which infrasound reportedly affects the brain, and at least one experiment with infrasound was unable to replicate the correlation between weird experiences and infrasound. But something seems to be happening: Bompas said that when his team tested the speakers — which, because typical commercial subwoofers are unable to go below 20 Hz, were custom-made by sound engineer firm TPI to pump out 19 Hz — the night before, he’d felt a ghostly hand clutching his throat.
. . .
WHICH IS PERHAPS why infrasound can be a useful tool for times when you want to be scared — for example, at haunted houses. Margee Kerr is an American sociologist who studies what role fear plays in our lives and why we like to be scared; her lab was Pittsburgh’s ScareHouse, widely considered one of the scariest haunted house attractions in America. Kerr employed infrasound there. “It generally gives people a feeling of creepiness, is the best word,” she explained. “It’s a great way to tap into a physical response that they don’t have any control over, in a safe way.”
Kerr says infrasound showed no effect beyond 10 or 15 feet from the subwoofer producing it, but when participants were in the zone, the effects were striking. Anxiety, a faster heartbeat, the feeling of a weight settling on one’s shoulders — these are the symptoms of a sympathetic nervous system being activated without any immediate explanation.
Using infrasound to produce these effects in humans is a bit like conjuring a ghost or spirit in a lab, offering tangible evidence of the kinds of physical sensations people report when having a ghostly experience. It’s significant that Tandy, who died in 2005, chose to publish his findings in the Journal of the Society of Psychical Research — basically, researchers trying to explain or validate “paranormal” experiences.
Infrasound can be produced naturally; some rare humans can even sing in barely audible infrasound frequencies. Animals, including whales, elephants, rhinos, lions, and tigers, use infrasound to communicate, and huge, destructive events such as volcanic eruptions, earthquakes, tornadoes, and tsunamis, produce infrasound waves. The 1883 eruption of Krakatoa, for example, produced infrasound waves that circled the earth several times and were recorded on contemporary instruments around the globe. That we might be evolutionarily primed to feel anxious or overawed around infrasound is probably not surprising, given that it is typically associated with things that might kill us.
Unintentional human-made infrasound is produced, handily enough, by huge, resonating instruments such as church organs. Wiseman reported in “Quirkology” that “people who experience a sense of spirituality in church may be reacting to the extreme bass sound produced by the pipes.” But it can also be produced by, for example, the wind blowing through a corridor or over a window open just so, by nearby traffic, rumbling motors, HVAC systems.
Kerr, like Tandy before her, thinks that naturally occurring infrasound could be a credible explanation for mysterious experiences attributed to the paranormal. “I think it’s definitely possible, especially with old buildings where there are so many broken HVAC systems and wind tunnels and just the opportunity to create that disturbance is really high,” she said. “We may not hear it, but our body is going to respond to it.”
Ironically, even as science helps us explain more of the phenomena our forebears attributed to supernatural events, the proliferation of heavy equipment works in the opposite direction. The percentage of Americans professing to believe in ghosts has crept up in recent years; the number of potential human-made sources of infrasound has grown as well. If an extractor fan in a janitorial closet could induce visions, then why couldn’t the cacophony of rumbling, thrumming stuff we surround ourselves with as well? More machines, more ghosts?
Linda Rodriguez McRobbie is an American freelance writer living in London.