The Shepard Tone Is A Sonic Barber Pole

The Shepard tone is an auditory illusion that has been described as a “sonic barber pole.“ In the same way that the classic red-and white-striped barber pole seems to perpetually spin upward when it’s just staying still, Shepard tone seem to infinitely rise or fall in pitch. This sound is made of multiple sine waves that trick our brain. The tones in the sound do rise, but when they reach a certain point they hop back down an octave and start again. However, our brains don’t hear that jump, instead they hear the tones rising or falling forever.