What is the name for the auditory illusion of a note that seems to be rising infinitely?

Shepard Tone is an auditory illusion created by layering several tones an octave apart and smoothly adjusting their volumes as the scale ascends. As higher tones fade out and new low tones fade in, your brain hears a pitch that seems to climb forever—yet it never gets higher overall. This crossfading trick convinces us of an infinite rise (or fall) in pitch. Named after cognitive scientist Roger Shepard (1964), the effect is widely used in film and game soundtracks to build tension—famously in movies like Inception and Dunkirk. A continuous version is called the Risset glissando. Memory tip: picture a “Shepard staircase” of sound—like an Escher staircase for your ears—where each step is an octave, and you keep walking up but never reach the top.