Shepard tones shift harmonics within a fixed envelope to create circular pitch

Evidence

The amplitudes of the components are constrained within the curved envelope shown. Each time the tone moves up one semitone, the partials all move up by a twelfth of an octave, or one semitone. The upper harmonics become weaker and eventually disappear, and new lower harmonics appear and become stronger. — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 1643

Categorization

• DEFINE: Explains the amplitde-envelope mechanism that produces the Shepard tone illusion of endless ascent/descent.
• XREF: Connects to any prior chapter discussion of pitch circularity or the missing fundamental, since the envelope hides which partials are audible. — connects to: A Shepard tone creates an endlessly ascending pitch while staying within one octave; Shepard tones create endlessly rising pitch through shifting autocorrelation peaks — Eric J. Heller, Why You Hear What You Hear- An…, 2121; Uniformly shifting a harmonic complex tone’s components changes pitch non-monotonically with a sawtooth pattern — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 720 (+5 more)

Broader Connections

• A Shepard tone creates an endlessly ascending pitch while staying within one octave #corroborates (1.00)
• Shepard tones create endlessly rising pitch through shifting autocorrelation peaks #corroborates (1.00) — Eric J. Heller, Why You Hear What You Hear- An…, 2121
• Uniformly shifting a harmonic complex tone’s components changes pitch non-monotonically with a sawtooth pattern #complicates (0.90) — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 720
• Harmonically shifted complex tones isolate fine structure cues while holding envelope constant #corroborates (0.90) — Dijk, Pim van, Physiology, Psychoacoustics and…, 4611
• Shifted complex tone pitch depends on envelope-fine-structure interaction, not fine structure alone. #corroborates (0.80) — Dijk, Pim van, Physiology, Psychoacoustics and…, 4659
• Shifting harmonic components changes fine structure while keeping envelope identical #corroborates (0.80) — Dijk, Pim van, Physiology, Psychoacoustics and…, 4615
• Amplitude modulation of noise creates pitch with a flat spectrum #complicates (0.70) — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1110
• Shifting harmonic partials upward raises perceived pitch despite unchanged envelope modulation #complicates (0.70) — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1119