That uncomfortable feeling you get in a “spooky” place may have a perfectly scientific explanation. New research suggests that getting creeped out in a basement, old building, or other unsettling area may be due to very low-frequency sound — not paranormal activity.
The study identifies the cause of this feeling as infrasound: noise below 20 Hertz, which humans usually can’t hear. It can come from a range of sources, including storms, traffic, and vibrating plumbing pipes.
The study makes a case for viewing infrasound as a form of noise pollution. Here’s how infrasound impacts the body, plus why humans may interpret it as paranormal activity.
Infrasound May Stress the Body by Raising Cortisol
Published in Frontiers in Behavioral Neuroscience, the study recruited 36 adults and asked them to sit alone in a room. During that time, participants heard calming or unsettling music. Researchers also exposed half of the participants to 18 Hertz infrasound.
After the exposure, the participants reported how they felt, their emotional reaction to the music, and whether they thought they were in the infrasound exposure group. The participants also gave saliva samples before and after exposure to infrasound.
The researchers discovered that the participants had higher levels of the stress hormone cortisol in their saliva after infrasound exposure, regardless of the type of music they heard. Participants also said that they felt more irritated after this exposure.
Among the group exposed to infrasound, adults were more likely to say the music was sadder after the exposure. However, the participants were not able to correctly identify if they had been exposed to infrasound.
“Animal studies provide us with great behavioral and physiological data, but we are limited in that we can’t simply ask a fish, for example, to tell us what it is feeling when exposed to infrasound,” Scatterty says. “On the other hand, humans can give us a bounty of information about how they feel about a stimulus, but administering that stimulus to them without their awareness and measuring what they are experiencing on a biological level have historically been challenging.”
This study allowed the researchers to take animal lab studies into a controlled study on humans, Scatterty explains. “If infrasound exposure is indeed doing something negative, then getting a more specific idea of how it affects us could bring us one step closer to identifying what could potentially be a psychologically important noise pollutant,” he says.
There Are a Few Possible Reasons Why the Brain May Make the Leap to Paranormal Activity
With infrasound exposure, it seems the human body senses a threat, but isn’t able to pinpoint the source, Scatterty says.
To explain the human tendency to jump to ghosts as a conclusion, Scatterty points to fish biology. “In fish species, it has long been suspected that infrasound detection occurs in the otolith organs, which [fish] use to get a sense of how they are oriented in a 3D space and whether threats like predators are close by,” he says. “We believe that humans may respond to infrasound in a non-auditory way through evolutionarily similar pathways.”
When humans are exposed to infrasound, they likely produce more cortisol because they sense some kind of danger, Scatterty says. “It is possible that infrasound acts as a subtle environmental stressor that one cannot hear, but can still [detect] on some lower-level sense and be disturbed by in some way,” he says.
The leap to blaming paranormal activity may simply be due to evolution, says Aaron P. Brinen, PsyD, an assistant professor of psychiatry and behavioral sciences at Vanderbilt University Medical Center in Nashville, Tennessee.
“Our brain is designed with a few small survival rules in place,” he says. “It’s better to think there is a lion in the bushes and be wrong, than to think there is no lion in the bushes and be wrong. Being able to detect danger earlier keeps you safer and relying on the side of caution keeps you safer.”
People are also “wired” to make meaning out of an unexplained arousal, says Thea Gallagher, PsyD, a clinical associate professor of psychology at NYU Langone Health in New York City. “In psychology, we’d call this misattribution of arousal. People may accurately sense physiological activation, but misidentify its source,” she says.
“If that occurs in a context already primed for mystery, like an old, ‘haunted’ building, the brain may interpret that unease through available cultural narratives about ghosts or presences,” Dr. Gallagher says. “In that sense, the leap to a paranormal explanation may be less irrational than it is a very human attempt to explain an invisible stress signal.”
The setting may matter with the way the body interprets infrasound, Dr. Brinen says. “If you’re experiencing this in an office building, you may interpret this as the FBI or your boss is watching you,” he says.
Is Infrasound Exposure Harmful to Health?
Infrasound generally makes people feel uneasy, but it’s difficult to say what the long-term impact of exposure would be. “We would not want people to walk away thinking that any exposure to infrasound is automatically harmful,” Scatterty says, noting that his research looked at short-term exposure under controlled conditions.
However, Scatterty says that infrasound may have noticeable effects, which warrants further research, especially in environments where exposure is repeated or drawn out.
“What we do know is that prolonged elevations in cortisol can indeed have detrimental effects on the body — sleep disruption, impaired immune function, high blood pressure, digestive issues, mood disturbances, impaired memory, and concentration — which is certainly motivation enough to start asking whether being in regular proximity to infrasound may be detrimental to one’s physical and mental health,” he says.
There Is an Important Takeaway, According to Experts
Scatterty stresses that more work is needed on the health impact of infrasound. “Much like regular exposure to many hazardous particles can be both invisible yet concerning for our health, it is easy for us to overlook sound outside our typical range of hearing,” he says. This is particularly true for those who are not aware of what infrasound even is, never mind where it comes from or how it seems to affect us.”
But Gallagher also notes that the findings validate creepy, unexplained feelings people may experience. “It reframes so-called paranormal experiences not as people imagining things, but as an interaction between physiology, perception, and meaning-making,” she says. “That’s a much more interesting psychological story.”