Overview
- Scientists report that inaudible low‑frequency sound at 18 hertz raised salivary cortisol and increased negative mood in a controlled lab experiment.
- Thirty‑six volunteers sat alone listening to calming or unsettling music while hidden subwoofers played infrasound for half the sessions, with saliva taken before and after to measure stress hormones.
- Participants could not tell when infrasound was present, and beliefs about exposure did not predict changes in cortisol or mood.
- The authors caution that the sample was small and only one frequency was tested, and they are calling for larger studies across more tones, longer exposures, and more diverse participants.
- The team is now measuring low‑frequency noise at reputedly haunted sites and has not consistently found elevated levels, noting that common sources such as ventilation systems, aging pipes, traffic, and machinery can also produce infrasound.