Study Suggests "Haunted" Houses May Be Due to Infrasound from Pipes, Furnaces, and Ventilation Systems
The unsettling, creepy, or even "watched" feeling some people experience in old houses is often attributed to ghosts. However, a new study suggests a more common cause: infrasound – low-frequency sound inaudible to the human ear – from old pipes and furnace systems.
A research team played infrasound, below 20 Hertz and beyond the range of human hearing, to volunteers in an experiment. They found that even when participants were unaware of the sounds, they exhibited increased irritability, more negative emotions, and elevated levels of the "stress hormone" cortisol. The authors of the paper point out that even without conscious awareness, infrasound from old pipes, furnaces, and ventilation systems in basements can subtly affect a person's emotional and physical state.
This effect alone is not enough to convince someone a house is haunted. However, for those already predisposed to believing in the supernatural, such as visitors to dark old houses who have been told "this place is haunted," this unexplained physical discomfort can easily be interpreted as evidence of "spirits" and amplify subjective feelings of being haunted.
Dr. Rodney Schmaltz, a psychologist at McMaster University in Canada, has long studied why people believe in pseudoscience and supernatural claims. He suggests that infrasound may provide a "physical background noise" – a slight discomfort – in "haunted experiences," leaving room for the explanation "it's a ghost." He believes that people with different belief systems will attribute the same sensations very differently: for someone who doesn't believe in ghosts, it might just be a "damp and old house," while for someone "pre-set" by a "haunted" narrative, the same sensation can be taken as proof of "ghostly presence."
In a previous experiment, the research team tested whether subtly adding infrasound to the visitor route at the local "haunted house" themed attraction Deadmonton would make visitors feel more afraid. The results at the time were inconclusive, prompting them to design a new experiment with stricter controls.
In the latest study, 36 volunteers listened to two types of music: calming instrumental music and eerie music similar to "haunted house soundtracks." Throughout the process, researchers intermittently played infrasound through hidden subwoofers without the subjects' knowledge.
The paper was published in *Frontiers in Behavioral Neuroscience*. The study showed that subjects could not distinguish whether the infrasound was on or off in their subjective reports, but when infrasound was present, they were more likely to feel irritated, annoyed, and rated the music as more "sad," with increased cortisol levels in their saliva samples. Schmaltz says that infrasound pushes the subjects' emotional and stress responses in a more negative direction, whether paired with soothing or unsettling music. In layman's terms, "you can't hear infrasound, but your body and emotions seem to react to it, and that reaction is often unpleasant."
Schmaltz believes that larger-scale studies are still needed to validate these findings. However, he speculates that infrasound is likely a partial source of the vague feeling of "something's not right, but I can't put my finger on it" that is common among those who firmly believe they are living in a haunted house. "These people often don't know what infrasound is; they've just been told they're in a haunted location, so they naturally attribute the annoyance or discomfort to ghosts, rather than the low rumble of old pipes in the basement," he says.
British psychologist and author of *The Science of Weirdness: Why Our Brains Conjure the Supernatural*, Chris French, points out that research results on the effects of infrasound have been complex and inconsistent. He believes that the sensations caused by infrasound may make some people more likely to perceive a place as "haunted," which is "reasonable in theory," but the explanation ends there. "To use infrasound to explain so-called 'poltergeist' phenomena, such as books flying off shelves or objects moving inexplicably, may be going too far," he says.
French adds that there is also a view that infrasound can cause vibrations in the eyes, inducing visual hallucinations such as "seeing ghosts." However, this claim is currently based mainly on anecdotal evidence and has not been strongly supported by rigorous, controlled scientific experiments.