Infrasound refers to infrasound waves below 20 hertz (Hz), which are generally above the range of human hearing. These vibrations can come from human sources such as traffic and industrial equipment, as well as natural phenomena such as storms. In the animal world, some species rely on infrasound to communicate, while others actively avoid it.
When scientists investigated whether people can perceive infrasound, they found that we are not consciously aware of it. But our bodies still react. Exposure is associated with increased irritability and elevated levels of cortisol, a hormone associated with stress.
“Infrasound is pervasive in everyday environments, occurring near ventilation systems, transportation, and industrial machinery,” said MacEwan University’s Professor Rodney Schmalz, lead author of the paper. Frontiers of behavioral neuroscience. “Many people are unknowingly exposed to such sounds. Our findings suggest that even short periods of time can alter mood and increase cortisol. This highlights the importance of understanding how infrasound affects people in real-world environments.”
“Think of visiting a building that is said to be haunted. You feel a change of mood and excitement, but you don’t see or hear anything out of the ordinary. In older buildings, especially dilapidated pipes and ventilation systems create low-frequency vibrations. If you are told that a building is haunted, you may think that the excitement is due to something supernatural.In reality, you may simply be exposed to infrasound.
Testing the effects of infrasound on mood and stress
To investigate these effects, the researchers recruited 36 participants for a controlled experiment. Each person sat alone in a room and listened to either calming or anxiety-provoking music. In half of the groups, the hidden subwoofer also produced 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 was present. The researchers also collected saliva samples before and after the listening period to measure cortisol levels.
Infrasound increases cortisol and irritability
The results revealed clear physiological and emotional changes. Participants exposed to infrasound showed higher levels of salivary cortisol. They also reported being more irritable, less engaged, and more likely to perceive music as sad. Despite these changes, it was not possible to determine with certainty whether infrasound was being reproduced.
“This study suggests that the body can respond to infrasound even when we cannot consciously hear it,” Schmalz said. “Participants could not reliably identify whether infrasound was present, and beliefs about whether infrasound was present had no detectable effect on cortisol or mood.”
“When you feel irritable or stressed, cortisol tends to rise as part of the body’s normal stress response, so increased irritability and increased cortisol are naturally associated,” said lead author Cale Scatterti, a doctoral student at the University of Alberta. “However, exposure to infrasound affected both outcomes beyond their natural relationship.”
You can feel it, but you can’t hear it: the hidden effects on your body.
The findings suggest that although humans cannot consciously detect infrasound, our bodies somehow record it. The exact biological mechanism is still unknown. Researchers also note that long-term exposure may affect health by keeping cortisol levels elevated, contributing to ongoing irritability and depressed mood.
“Elevated cortisol levels help the body respond to impending stressors by inducing a state of alertness,” said corresponding author Professor Trevor Hamilton from MacEwan University. “This is an evolutionarily adapted response that helps us in many situations. However, prolonged cortisol release is not a good thing. It can cause various physiological states and alter mental health.”
What scientists still have to learn
Because the study included a relatively small group, the researchers performed additional analyzes to confirm their findings. These checks showed that the experiment was capable of detecting moderate to large effects, including the observed changes. Still, larger and more diverse studies will be needed to fully understand how infrasound shapes human emotions and behavior.
“In many ways, this study was a first step toward understanding the effects of infrasound on the human body,” Scatterti cautioned. “So far, we have only tested certain frequencies; there may be many more frequencies and combinations that have their own different effects. We also only collected subjective reports of how participants felt after exposure, without directly observing participants’ reactions during the experiment.”
“The first priority is to test a wider range of frequencies and exposure times,” Schmalz added. “Infrasound in real environments is rarely a single clean sound, and we don’t yet know how different frequencies and combinations affect mood and physiology. As these patterns become clearer, the findings could ultimately inform noise regulations and building design standards.” As such, what struck me is that infrasound produces a real, measurable response even without a visible or audible source. So the next time you feel some unexplained discomfort in a basement or an old building, consider that the cause may be “vibrating pipes instead of restless spirits.” ”
