A study, published in Frontiers in Behavioral Neuroscience, suggests that infrasound — very low-frequency sound below 20 Hz that humans cannot consciously hear — can increase stress, irritability, and cortisol levels, potentially explaining many reported “paranormal” experiences in supposedly haunted buildings.
Key findings
- Brief exposure to infrasound (at 18 Hz) caused participants to feel more irritable, less interested, and to rate music as sadder, even though they couldn’t detect or consciously hear the infrasound.
- Salivary cortisol (a stress hormone) levels rose significantly after exposure.
- The effects on mood and cortisol went beyond the normal link between stress and irritability, indicating a specific physiological response to infrasound.
- Participants were unable to guess whether infrasound was present, and their prior beliefs did not influence the results.
Study details
36 participants were tested. Participants sat alone listening to music while hidden subwoofers played infrasound for half of them. Mood, emotional ratings of the music, and saliva samples (for cortisol) were collected before and after.
Implications
Infrasound is common in everyday environments from sources like ventilation systems, traffic, industrial machinery, or even vibrating pipes in old buildings. The authors propose that unexplained feelings of unease, agitation, or “haunted” sensations in such places may actually result from infrasound rather than supernatural causes.
Quotes from the researchers:
- Prof. Rodney Schmaltz: “Consider visiting a supposedly haunted building… you may simply have been exposed to infrasound.”
- Kale Scatterty: “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.”
- Prof. Trevor Hamilton noted that while short-term cortisol increases help handle immediate stress, prolonged elevation can harm physical and mental health.
Limitations and next steps
The sample was small and not very diverse. The study used a single frequency and short exposure; real-world infrasound is often more complex. The authors call for further research on different frequencies, longer exposures, and broader health impacts.
Overall takeaway: Infrasound produces real, measurable effects on mood and stress hormones without us being aware of it, offering a scientific explanation for some experiences traditionally attributed to ghosts or spirits.
