A new study suggests people may physically react to infrasound even when they cannot consciously hear it. Researchers found that exposure to low-frequency sound was linked to increased irritability and higher cortisol levels, which may help explain why some environments feel unsettling or “haunted” for no apparent reason. Infrasound refers to sound below 20Hz, a frequency range that humans usually cannot hear. It can come from natural sources, such as storms, as well as human-made sources, including traffic, industrial machinery, and ventilation systems.

Infrasound refers to sound below 20Hz, a frequency range that humans usually cannot hear. It can come from natural sources, such as storms, as well as human-made sources, including traffic, industrial machinery, and ventilation systems.

Professor Rodney Schmaltz of MacEwan University said the findings suggest the body may respond to infrasound even without conscious awareness. He added that infrasound is common in older buildings where pipes and ventilation systems can generate low-frequency vibrations, potentially contributing to feelings people associate with haunted locations.

The study, published in Frontiers in Behavioral Neuroscience, involved 36 participants who sat alone in a room while listening to calming or unsettling music. Half of the participants were also exposed to hidden subwoofers producing infrasound at 18Hz.

After the sessions, participants rated the emotional tone of the music, described how they felt, and provided saliva samples before and after exposure. According to the researchers, those exposed to infrasound showed higher cortisol levels and reported feeling more irritable, less interested, and more likely to perceive the music as sad.

However, participants could not reliably determine whether infrasound had actually been present during the experiment.

Researcher Kale Scatterty said the effects of infrasound on cortisol and irritability appeared to go beyond the body’s normal stress response.

The researchers also warned that prolonged cortisol elevation could eventually affect physical and mental health. Professor Trevor Hamilton noted that while cortisol helps the body respond to immediate stress, long-term exposure may contribute to physiological and mental health problems.

The study authors cautioned that the research involved a relatively small number of participants and tested only one specific frequency. They said larger studies examining different frequencies and exposure durations will be needed to better understand how infrasound affects human behavior, mood, and physiology.

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