Inaudible infrasound from aged pipes, boilers, and ventilation systems may be responsible for the unsettling feelings often attributed to haunted buildings, according to new research. Scientists found that even when participants could not hear the low-frequency sound waves, they reported increased irritability and had higher levels of the stress hormone cortisol.
The study, published in Frontiers in Behavioural Neuroscience, involved 36 volunteers who listened to either calming instrumental music or unsettling tracks typically used in haunted house attractions. Without their knowledge, researchers played infrasound through hidden subwoofers during half of the sessions. Participants could not detect the infrasound, but when it was present, they rated the music as sadder, felt more annoyed, and had elevated cortisol levels in their saliva.
Professor Rodney Schmaltz, a psychologist at MacEwan University in Canada and lead author, explained that infrasound may cause bodily discomfort that people, especially those inclined to believe in the paranormal, might interpret as evidence of ghosts. “For someone who is not inclined to think in terms of ghosts, the same sensation would probably just register as a stuffy, uncomfortable old building,” he said. “For someone who is already primed, it might feel like proof of a spirit or presence.”
Earlier experiments at a haunted house attraction called Deadmonton had yielded inconclusive results, prompting the more controlled laboratory tests. Schmaltz noted that larger studies are needed to confirm the effect, but the findings suggest infrasound could contribute to the “vague discomfort” reported in supposedly haunted locations.
Chris French, emeritus professor of psychology and author of The Science of Weird Shit: Why Our Minds Conjure the Paranormal, described the research as “plausible” but cautioned against overinterpretation. “It may be a step too far to explain alleged poltergeist activity, such as objects flying off shelves, as resulting from infrasound,” he said. He also dismissed claims that infrasound causes visual hallucinations, noting such speculation is based on anecdotal evidence without support from controlled studies.
