The human ear can only hear a limited part of the sound spectrum. Above that range is ultrasound and below it is infrasound; although largely unheard, vibrations in these ranges can still affect the human body in ways that are quite different from the informational aspect of simply listening. These higher and lower registers of sound frequencies are, today, the stuff of imaginative speculation. While the conspiracy watchers believe they are the basis of secret weapons research for covert operations, mind control and other conspiratorial uses, another, more idealistic, school associates them with meditative states and magical technology. The wilder fortean literature attributes to the builders of ancient monuments everywhere the secret of levitating blocks of stone by their mastery of sound; such powers were supposedly also used by the Vedic gods to power their vimana flying ships.

The use of disconcerting noise to unsettle the enemy is hardwired into most higher animals, from the warnings and battle roars of confrontational beasts to the trumpets, drums, bugles, bagpipes, devilish war cries, taunts and piercing shrieks used by humans in their conflicts.