The creepy feeling in old buildings might have a surprising cause

When scientists examined whether people can perceive infrasound, they found that we are not consciously aware of it. However, our bodies still react. Exposure has been associated with increased irritability and higher levels of cortisol, a hormone linked to stress.

"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."

Testing How Infrasound Affects Mood and Stress

To explore these effects, researchers recruited 36 participants for a controlled experiment. Each person sat alone in a room while listening to either calming or unsettling music. For half of the group, hidden subwoofers also generated infrasound at 18 Hz.

After the session, participants described how they felt, rated the emotional tone of the music, and indicated whether they believed infrasound had been present. Researchers also collected saliva samples before and after the listening period to measure cortisol levels.

Infrasound Raises Cortisol and Irritability

The results revealed clear physiological and emotional changes. Participants who were exposed to infrasound showed higher levels of salivary cortisol. They also reported feeling more irritable, less engaged, and more likely to perceive the music as sad. Despite these changes, 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: Hidden Effects on the Body

The findings suggest that while humans cannot consciously detect infrasound, the body still registers it in some way. The exact biological mechanism remains unknown. Researchers also note the possibility that long-term exposure could influence health by keeping cortisol levels elevated and contributing to ongoing irritability or low mood.

"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."

What Scientists Still Need to Learn

Because the study included a relatively small group, the researchers performed additional analyses to confirm their findings. These checks showed the experiment was capable of detecting moderate to large effects, including the changes observed. Still, larger and more diverse studies will be needed to fully understand how infrasound shapes human emotions 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."