A rising pitch can perceptually loop back to its start.

Evidence

One of the most famous auditory demonstrations is called the Shepard-Risset tones, or Shepard tones, after the inventors. By a very clever choice of the amplitudes and frequencies of the partials, Shepard tones present a rising pitch from one semitone to the next. But after 12 rising semitones, the pitch winds up where it started! This feat is frequently compared to the impossible Penrose stairs, a 2D drawing of a 3D staircase invented by the physicist Roger Penrose and his father (figure 23.15). Every step is up (or every one down in the other direction), and yet one returns to the starting place. The illusion springs from an ambiguity of a two-dimensional rendering of what is in reality a three-dimensional object. The Shepard-Risset tone illusion stems ultimately from a pitch ambiguity, and we shall analyze it in several ways, as it is quite revealing. — Eric J. Heller, Why You Hear What You Hear- An…, 2112

Categorization

Category: Contrarian or Surprising Claims

• XREF: Connects to the auditory-illusion literature alongside the Tritone Paradox and Deutsch’s auditory demonstrations.
• CANDY: The endlessly rising Shepard tone is a classic party-trick illusion, familiar to anyone who has heard it in film soundtracks.

Related

• A Shepard tone creates an endlessly ascending pitch while staying within one octave (similarity 0.84)
• A sound can rise in pitch forever without ever rising in frequency (similarity 0.83)
• Shepard tones create endlessly rising pitch through shifting autocorrelation peaks (similarity 0.82)
• Endlessly accelerating beat rhythms are Shepard tones shifted down in frequency. (similarity 0.79)
• A perceived pitch can exist with no partial at its own frequency. (similarity 0.78)

Broader Connections

• A sound can rise in pitch forever without ever rising in frequency #expands (0.95) — David Howard, Jamie Angus, coustics and Psychoacoustics, 1683