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Shepard tone
Spectrum view of ascending Shepard tones (linear frequency scale) 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 upward or downward, 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 ] It has been described as a "sonic barber's pole ". [ 2 ] [ edit ] Construction Figure 1: Shepard tones forming a Shepard scale, illustrated in a sequencer