Study: Infrasound likely a key factor in alleged hauntings - Ars Technica

Overview

Study: Infrasound likely a key factor in alleged hauntings

Low-frequency infrasound (below 20 Hz) can raise cortisol levels in saliva and increase irritability.

Details

The next time you walk into a purportedly “haunted” house and sense a ghostly presence, consider that those feelings might be due to vibrating pipes, mechanical or climate control systems, rumbling from traffic, or wind turbines, rather than anything paranormal. That’s the conclusion of a new paper published in the journal Frontiers in Behavioral Neuroscience. All of those are sources of infrasound.

Scientists have long sought to find logical explanations for alleged hauntings. In 2003, for instance, University of Hertfordshire psychologist Richard Wiseman conducted two studies that investigated the psychological mechanisms underlying supposed “ghostly” activity. Subjects walked around Hampton Court Palace in Surrey, England, and the South Bridge Vaults in Edinburgh, Scotland—both with reputations for manifesting unusual phenomena—and reported back on which places at those sites they sensed such phenomena. The subjects reported more odd experiences in places rumored to be haunted, regardless of whether the subjects were aware of those rumors or not.

Those areas did, however, feature variances in local magnetic fields, humidity, and lighting levels, suggesting that such sensations are simply people responding to normal environmental factors. Wiseman hypothesized that stronger magnetic fields may affect the brain, similar to how electrical stimulation of the angular gyrus can make one feel as if there is another person standing behind, mimicking one’s movements.

Furthermore, 70 percent of subjects in a related study of Mary King’s Close—another “haunted” location—reported suddenly feeling cold, like they were being watched or touched, or heard unexplained footsteps. The areas where they felt those things had markedly lower humidity. The experiences are therefore “real” in the sense that people are feeling the sensations; they’re just not likely due to ghosts. And those sensations are heightened when there is an expectation of a place being haunted.

The late Vic Tandy, an engineer at Coventry University, proposed another explanation: infrasound, particularly at a frequency of 18.9 Hz. This is just below the range of human hearing, but research has shown that humans may still subconsciously sense such sounds. Tandy thought infrasound was the culprit of an alleged haunting in a laboratory in Warwick, as well as a suspected ghost in the cellar of Coventry Cathedral.

Tandy had a spooky experience while working late one night at the Warwick laboratory. He felt the hairs rise on the back of his neck just as he caught a glimpse of a gray apparition out of the corner of his eye, which disappeared when he turned to face it. He thought the effect was due to infrasonic vibrations from a newly installed extractor fan; when he switched it off, he felt as if a huge weight had been lifted. But Tandy died in 2005 before he could investigate further, particularly into why some people seem to be affected in this way by infrasound and others are not.

Rodney Schmaltz of Mac Ewan University, co-author of this latest study, told Ars that such infrasound effects have long been a subject he discusses in his course on science and pseudoscience. Part of that course involves taking students on “ghost hunts” to debunk standard ghost-hunting tools. They usually test for infrasound, among other things. “What I thought might be happening is a misattribution of arousal, in the sense that people would just feel something,” he said. “They’re in an old building, they attribute it to ghosts. I wanted to see if there really was a strong fear response that was enhanced by infrasound.”

This prompted a small study project with his students. They built their own infrasound speakers and took them to a commercial haunted house during off-hours when the usual actors providing jump scares weren’t present. Then they recruited subjects to walk through the house and report on the sensations they experienced. Schmaltz noticed that whenever they turned on the infrasound, people would walk through the house faster. “It was interesting, but it certainly was not enough to definitively say what impact infrasound was having,” he said.

A chance conversation with neuroscientist colleague (and co-author) Kale Scatterty inspired this latest study. Scatterty co-authored a 2023 paper demonstrating an aversion in zebrafish to infrasound, specifically an anxiety response that caused the fish to avoid certain tank areas. This suggested a physiological response to infrasound, and Schmaltz wanted to see if this was also true in humans. So they designed a lab-based experiment to test the hypothesis that cortisol levels in people’s saliva—part of the body’s normal stress response—would increase in response to infrasound.

Visual layout of the testing area and equipment used in producing infrasound.

Thirty-six participants sat alone in a room and were exposed either to calming music similar to what one might hear in a yoga setting, or “more unsettling ambient music,” per Schmaltz, with half of them also being exposed to infrasound emitted from hidden subwoofers. “What we thought might happen was when the infrasound was on, people would find the calming music even more relaxing, while the scarier music would be scarier,” he said.

Instead, the results showed that, across the board, participants felt more irritated and unsettled when the infrasound was turned on, regardless of which kind of music was playing, and their cortisol levels increased significantly. None of the participants could reliably tell when infrasound was present. This suggests that human beings can have a physiological response to infrasound even when we can’t consciously hear it.

While this is a promising result, infrasound is unlikely to be the sole factor behind our perceptions of hauntings; it’s probably one of several, including Wiseman’s earlier findings on suggestibility. “It’s not that infrasound is ‘causing’ hauntings,” said Schmaltz. “I want to be very clear on that. We’re definitely not saying we’ve solved hauntings. But in some of these older buildings, there could be low rumbling pipes [producing infrasound], and if somebody already has the expectation that something spooky might happen, the infrasound might drive that a bit. So infrasound doesn’t explain all of it, but it could certainly be a piece of the puzzle for some of these haunting experiences.”

It probably doesn’t explain Tandy’s strange visual illusion, however. “Tandy’s speculation was that the infrasound was making his eyes vibrate,” said Schmaltz. “I’m a bit skeptical. I just can’t imagine how you could generate that much infrasound.” His own experiments turned the decibel level quite high, as much as 75–78 d B, “but there was nothing along the lines of what Tandy experienced.”

Schmaltz readily acknowledges that his study has a very small, fairly homogenous sample size. That’s partly because testing saliva for cortisol levels is an expensive undertaking, and he only had an $8,000 grant to work with. He would love to expand on the work with a larger sample size, funds permitting. In the meantime, his team is visiting various supposedly haunted locations and measuring the infrasound levels to see if there is any difference between places thought to be haunted and those that are not. “We’re not finding much,” he admitted.

Future experiments might also expand the frequency range of the infrasound; the present study used infrasound in the 17–19 Hz range, about what one would get from a low-rumbling pipe or traffic. “We’re built to believe,” said Schmaltz of his ongoing efforts. “We’re hardwired to be belief engines. I’m just trying to promote tools to help people become better consumers of information, to identify when something sounds scientific but isn’t.”

Frontiers in Behavioral Neuroscience, 2026. DOI: 10.3389/fnbeh.2026.1729876 (About DOIs).

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Key Takeaways

Study: Infrasound likely a key factor in alleged hauntings
Low-frequency infrasound (below 20 Hz) can raise cortisol levels in saliva and increase irritability
The next time you walk into a purportedly “haunted” house and sense a ghostly presence, consider that those feelings might be due to vibrating pipes, mechanical or climate control systems, rumbling from traffic, or wind turbines, rather than anything paranormal
Scientists have long sought to find logical explanations for alleged hauntings
Those areas did, however, feature variances in local magnetic fields, humidity, and lighting levels, suggesting that such sensations are simply people responding to normal environmental factors