The Silent Frequency That Makes Old Buildings Feel Haunted

Source: Slashdot

Background

Researchers say infrasound — low‑frequency vibrations from things like pipes, HVAC systems, and traffic that humans can’t consciously hear — may help explain why some old buildings feel unsettling or “haunted” ScienceBlog.com. Rodney Schmaltz, senior author and professor at MacEwan, notes that infrasound often occurs in basements where aging pipes and ventilation systems produce low‑frequency vibrations. When people are told a building is haunted, they may attribute any agitation to the supernatural, when it could simply be exposure to infrasound.

Infrasound sits below roughly 20 Hz, the lower limit of ordinary human hearing. It is generated by natural phenomena (storms, volcanic activity, tectonic rumblings) and by everyday mechanical sources such as ageing pipes, HVAC systems, traffic, and industrial machinery. “Infrasound is pervasive in everyday environments, appearing near ventilation systems, traffic, and industrial machinery,” says Schmaltz. Most of the time we walk through it without a second thought. The research team wanted to know whether walking through it actually affects us, even if the frequency is registered below conscious awareness.

Experimental Setup

Thirty‑six undergraduate students were tested individually in isolated rooms. Each participant listened to a piece of music—either a calming instrumental or a horror‑themed ambient track designed to provoke discomfort. Hidden subwoofers (a 12‑inch unit in an adjacent hallway and a 16‑inch speaker oriented toward the ceiling in a neighboring room) pumped infrasound at approximately 18 Hz into half of the testing spaces. Participants were unaware of the infrasound condition.

Results

• Participants could not reliably identify whether infrasound was present; their guesses were no better than chance.
• Beliefs about the presence of infrasound had no detectable effect on cortisol levels or mood.
• Those exposed to infrasound reported:
  • Higher irritability
  • Lower interest in the music
  • A tendency to rate the music as sadder (regardless of whether it was calming or horror‑themed)
• Cortisol levels measured before and about 20 minutes after exposure were elevated.

Kale Scatterty, the PhD student who led the work, observed that irritability and cortisol often move together under ordinary stress, but “infrasound exposure had effects on both outcomes that went beyond that natural relationship.” Anxiety measures did not change significantly, suggesting that the effect is more about irritability and low‑grade aversion than fear.

Implications

Previous theories linked infrasound to paranormal experiences via anxiety‑driven dread. The new data suggest a different mechanism: infrasound induces irritability and a sour, uneasy atmosphere rather than outright fear. This may better describe the subtle sense of unease that characterizes many ghost stories.

Publication

The study was published this week in Frontiers in Behavioral Neuroscience: https://www.frontiersin.org/journals/behavioral-neuroscience/articles/10.3389/fnbeh.2026.1729876/full.