In my meanderings around the web I came across various articles about infrasound, the world of sound below ~19 Hz (cycles per second) and how it can affect the animal world. Experimental pieces of music, laced with infrasound, have been presented to audiences who have related experiences of nausea, anxiety, fear and dislocation. It has also been suggested that animals can predict catastrophic events from ultrasound vibrations they can sense. For example, animals were seen to flee before the Tsunami hit in 2004, perhaps sensing the infrasound travelling through the earth heralding the catastrophe. Whether this is myth or fact, I don’t know, but interesting nevertheless. The resonant frequency of the human eye is around 18 Hz, and reports of visions and ghosts have been accounted for by the presence of low frequency sound interacting with the eye giving rise to visions.