A recent study, inspired by a conversation between neuroscientist Kale Scatterty and lead researcher Schmaltz, investigated how infrasound—sound below the range of human hearing—affects stress responses in humans. This research follows Scatterty’s 2023 paper, which found that zebrafish exhibit anxiety and avoidance behaviours in response to infrasound. The aim was to determine whether humans experience similar physiological stress responses, specifically an increase in cortisol levels, which is a hormone associated with stress.
In a controlled lab experiment, thirty-six participants were isolated in a room and exposed to either calming music, typical of a yoga class, or unsettling ambient sounds. Half of the participants also received exposure to infrasound produced by concealed subwoofers. Expectations suggested that infrasound would amplify feelings of relaxation with calming music and intensify discomfort with unsettling sounds.
Contrary to these predictions, the results indicated that participants universally felt more irritated and unsettled during infrasound exposure, regardless of the type of music. Further, cortisol levels rose significantly among those exposed to infrasound. Notably, participants were unable to reliably detect the presence of infrasound, highlighting a potential unconscious physiological response to this kind of sound.
Though these findings are significant, Schmaltz cautioned against attributing hauntings solely to infrasound. He emphasised that while it may contribute to certain eerie experiences, several other factors exist, including suggestibility, which has been previously explored in the context of ghostly perceptions. As such, infrasound may be one element among many that influence human responses to supposed hauntings.
The research opens avenues for further investigation into how infrasound interacts with human perception and emotion in various contexts.
Test Your Understanding
How much do you know?
