Study: Infrasound likely a key factor in alleged hauntings

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 MacEwan 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. 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 dB, “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).