The Story of an Engineer Who Found Inaudible Infrasound Caused the Paranormal Activity Reported at Famous “Haunted” Sites [5:27]

TLDR: The human eyeball’s resonant frequency is 19 Hz. Infrasound (sound outside our hearing range) at that frequency will cause visual distortions and “apparitions”.
(https://higgs.ph.ed.ac.uk/outreach/higgshalloween-2021/haunted-frequency).