Scientists Identify Hidden Effect That Makes Old Buildings Feel Haunted

Scientists may have found a very earthly explanation for why old buildings can feel so unsettling. Research published in the journal Frontiers in Behavioral Neuroscience suggests that low-frequency sound vibrations, known as infrasound, can raise stress levels and darken a person's mood, even when they cannot hear anything at all.

Infrasound refers to any sound below roughly 20 hertz, which is the lower limit of what human ears can consciously detect. Despite being inaudible, these vibrations travel easily through walls and other obstacles and are commonly produced by ageing pipes, ventilation systems and industrial machinery. They are also found in nature, generated by storms, earthquakes, volcanoes and even the northern lights.

Rodney Schmaltz, a psychologist at MacEwan University in Canada and the study's senior author, said the findings could help explain why people visiting old or supposedly haunted buildings sometimes feel a sudden sense of unease. In basements and older structures in particular, creaking pipes and worn-out ventilation systems are likely sources of infrasound. If someone already believes a building to be haunted, he said, they may well put that feeling of agitation down to something supernatural rather than to their surroundings.

To test the effects, the research team recruited 36 undergraduate students and asked them to sit alone in a room listening to either calming or unsettling music. For half of the participants, hidden subwoofers also played infrasound at 18 hertz, though none of the students were aware of this. Afterwards, participants completed a survey about how the music had made them feel, and provided saliva samples before and after the session so that cortisol levels could be measured. Cortisol is a hormone the body releases in response to stress.

Those who had been exposed to infrasound reported feeling more irritable and uncomfortable, and rated the music as sadder, even when they had been listening to the calming track. Crucially, they showed a significant rise in cortisol compared to those who had not been exposed to the vibrations, and none of them were able to tell whether the infrasound had been present.

Kale Scatterty, a behavioural neuroscientist at the University of Alberta and the study's lead author, noted that while irritability and raised cortisol naturally go hand in hand, the infrasound appeared to affect both outcomes in ways that went beyond that expected relationship.

The researchers believe humans may be hardwired to react negatively to infrasound, much as some animals are thought to respond to the low-frequency vibrations that precede earthquakes and tsunamis. If so, what feels like a ghostly atmosphere may simply be the body's ancient alarm system being triggered by inaudible noise.

The study's authors acknowledge the sample size was small and that further research is needed. Only one frequency was tested, and other combinations of infrasound may produce different effects. Even so, the findings could have practical implications for how buildings are designed and how noise regulations are drawn up.