Sonic Movements

A Shepard tone, named after Roger Shepard, is a sound consisting of a superposition of sine waves separated by octaves. When played with the base pitch of the tone moving upwards or downwards, it is referred to as the Shepard scale. This creates the auditory illusion of a tone that continually ascends or descends in pitch, yet which ultimately seems to get no higher or lower.[1]



In telecommunications, physics, and radio astronomy, heterodyning is the generation of new frequencies by mixing two or more signals in a nonlinear device such as a vacuum tube, transistor, diode mixer, Josephson junction, or bolometer. Mixing two frequencies creates two new frequencies, one at the sum of the two frequencies mixed, and the other at their difference. A heterodyne receiver is a telecommunication receiver which uses this effect to produce frequency shifts.

In acoustics, a beat is an interference between two sounds of slightly different frequencies, perceived as periodic variations in volume whose rate is the difference between the two frequencies.

When tuning instruments that can produce sustained tones, beats can readily be recognized. Tuning two tones to a unison will present a peculiar effect: when the two tones are close in pitch but not yet identical, the difference in frequency generates the beating. The volume varies like in a tremolo as the sounds alternately interfere constructively and destructively. When the two tones gradually approach unison, the beating slows down and disappears, giving way to full-bodied unison resonance.


The Brown Note
The brown note, according to an urban legend, is an infrasound frequency that causes humans to lose control of their bowels due to resonance. There is no scientific evidence to support the claim that a "brown note" (transmitted through sound waves in air) exists.