That Haunted Feeling May Be Caused by a Sound You Can’t Hear

People exposed to infrasound may not consciously hear it, but they can show higher cortisol levels and increased irritability, which may help explain reports of “haunted” locations.

Infrasound refers to sound at very low frequencies, below 20 Hertz (Hz), a range that people usually cannot hear. It can be produced by natural events such as storms, as well as human made sources such as traffic. Some animals use infrasound for communication, while others move away from it. In a new study of whether people can sense infrasound, scientists found that although humans do not consciously detect it, their bodies still react, with exposure linked to greater irritability and higher cortisol levels.

“Infrasound is pervasive in everyday environments, appearing near ventilation systems, traffic, and industrial machinery,” said Prof. Rodney Schmaltz of MacEwan University, senior author of the article in Frontiers in Behavioral Neuroscience. “Many people are exposed to it without knowing it. Our findings suggest that even a brief exposure may shift mood and raise cortisol, which highlights the importance of understanding how infrasound affects people in real-world settings.

“Consider visiting a supposedly haunted building. Your mood shifts, you feel agitated, but you can’t see or hear anything unusual. In an old building, there is a good chance that infrasound is present, particularly in basements where aging pipes and ventilation systems produce low-frequency vibrations. If you were told the building was haunted, you might attribute that agitation to something supernatural. In reality, you may simply have been exposed to infrasound.”

Sound of the underground

The researchers recruited 36 people and asked each of them to sit alone in a room while either calming or unsettling music played. Half of the participants were also exposed to hidden subwoofers producing infrasound at 18 Hz. Afterward, they described how they felt, rated the emotional tone of the music, and said whether they believed infrasound had been present. They also provided saliva samples before and after the listening session.

Participants who had been exposed to infrasound showed higher salivary cortisol levels. They also reported feeling more irritable, less interested, and more likely to perceive the music as sad. Even so, they could not reliably tell whether infrasound had been playing.

“This study suggests that the body can respond to infrasound even when we can’t consciously hear it,” said Schmaltz. “Participants could not reliably identify whether infrasound was present, and their beliefs about whether it was on had no detectable effect on their cortisol or mood.”

“Increased irritability and higher cortisol are naturally related, because when people feel more irritated or stressed, cortisol tends to rise as part of the body’s normal stress response,” said Kale Scatterty, first author and PhD student at the University of Alberta. “But infrasound exposure had effects on both outcomes that went beyond that natural relationship.”

Felt but not heard

The results suggest that people can respond to infrasound without consciously recognizing it, though scientists still do not know exactly how this happens. The findings also raise questions about whether longer exposure could affect health by keeping cortisol elevated or by contributing to mood related problems such as irritability and reduced well being.

“Increased cortisol levels help the body respond to immediate stressors by inducing a state of vigilance,” said Prof Trevor Hamilton of MacEwan University, corresponding author. “This is an evolutionarily-adapted response that helps us in many situations. However, prolonged cortisol release is not a good thing. It can lead to a variety of physiological conditions and alter mental health.”

Because the study included a relatively small group of participants, the scientists performed sensitivity analyses before interpreting the findings. They confirmed that the study was capable of detecting moderate to large infrasound effects, including the main results. Still, larger and more diverse studies will be needed to understand how infrasound affects human emotion and behavior.

“This study was in many ways a first step towards understanding the effects of infrasound on humans,” cautioned Scatterty. “So far, we’ve only tested a specific frequency. There could be many more frequencies and combinations that have their own differential effects. We also only collected subjective reports of how the participants felt after exposure, without directly observing their responses during the trial.”

“The first priority would be testing a wider range of frequencies and exposure durations,” added Schmaltz. “Infrasound in real environments is rarely a single clean tone, and we don’t yet know how different frequencies or combinations affect mood and physiology. If those patterns become clearer, the findings could eventually inform noise regulations or building design standards. As someone who studies pseudoscience and misinformation, what stands out to me is that infrasound produces real, measurable reactions without any visible or audible source. So, the next time something feels inexplicably off in a basement or old building, consider that the cause might be vibrating pipes rather than restless spirits.”

Reference: “Infrasound exposure is linked to aversive responding, negative appraisal, and elevated salivary cortisol in humans” by Kale R. Scatterty, Dawson VonStein, Lisa B. Prichard, Brian C. Franczak, Trevor J. Hamilton and Rodney M. Schmaltz, 6 March 2026, Frontiers in Behavioral Neuroscience.
DOI: 10.3389/fnbeh.2026.1729876

This project was funded by a Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant (03403) held by TH.

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