Talk:The Frequency/@comment-744328-20140118122121

This is actually basically true. Infrasound (lower than 20 hz) can produce such effects.

Humans can't hear it consciously, but our subconscious still "hears" it, and it often produces feelings of anxiety. It is an evolutionary thing, many natural catastrophes, such as earthquakes, give out infrasound before they really hit. Also e.g. tigers have infrasound "elements" in their roar, and the deeper the frequency is, the longer the sound travels, so the humans (or "prehumans") could be warned subconsciously of a danger.

That is the reason why many ghost sightings are often happening in places, where infrasound is created, such as in old big houses, or churches with organs, where the wind can blow and create the infrasound, and thus create the mystical feelings of dread and anxiety.

A special frequency is 18 hz, because it is supposedly the resonance frequency of the human eye, which means it can create vibration in the eye, which can lead to people seeing "ghosts" in the corner of their sight, and it probably also can create a "foggy" vision.