Low-frequency sound waves could explain ghostly hauntings, according to Coventry University researchers. Vic Tancy and Tony Lawrence found that trapped sound waves in a laboratory reputed to be haunted were causing the air to vibrate at a frequency known to affect human vision. Supposed spooky apparitions could be the result of blurred vision caused by low frequency vibrations in the eyeball, they concluded. Physiological symptoms, such as breathlessness and shivering, are also linked to exposure to ultrasound.