That Haunted Feeling May Be Caused by a Sound You Can’t Hear

A new study published in *Frontiers in Behavioral Neuroscience* reveals that humans exposed to infrasound—sound waves below 20 Hz that are typically inaudible—experience measurable physiological and emotional responses. Researchers at MacEwan University and the University of Alberta found that participants exposed to 18 Hz infrasound via hidden subwoofers showed higher cortisol levels and reported increased irritability, sadness perception, and reduced interest, despite being unable to detect the sound. The study involved 36 participants who listened to calming or unsettling music in a controlled setting, with half exposed to infrasound. Afterward, saliva samples revealed elevated cortisol in the exposed group, while their mood assessments indicated heightened agitation. Prof. Rodney Schmaltz, senior author, noted that infrasound is common in everyday environments like ventilation systems, traffic, and industrial machinery, suggesting it may contribute to unexplained mood shifts in places like old buildings often described as haunted. Participants could not reliably identify whether infrasound was present, and their beliefs about its presence had no effect on cortisol or mood. This implies the body responds subconsciously, though the exact mechanism remains unclear. Lead author Kale Scatterty, a PhD student at the University of Alberta, emphasized that infrasound’s impact on cortisol and irritability extends beyond typical stress responses, raising concerns about prolonged exposure. The findings also highlight potential health risks, as sustained cortisol elevation can lead to physiological and mental health issues. Prof. Trevor Hamilton, corresponding author, warned that while short-term cortisol spikes aid stress responses, chronic exposure may disrupt well-being. The study underscores the need for further research into infrasound’s long-term effects in real-world settings, where exposure is often unavoidable. Infrasound may help explain why people feel uneasy in certain environments without identifiable causes. Schmaltz suggested that aging buildings, with their creaking pipes and ventilation systems, are likely sources of such vibrations. The study’s results challenge assumptions about human perception, showing that physiological reactions can occur independently of conscious awareness.