The Infinite Auditory Illusion

The Shepard tone is an audio trick that sounds like it is constantly climbing higher or lower in pitch forever. Despite this clear sense of movement, the pitch never actually leaves its original range.

This sonic trick works by layering several tones separated by octaves. As one tone fades out at the top of the spectrum, another simultaneously emerges at the bottom to take its place. Your brain perceives this seamless loop as a continuous ascent, even though the pitch stays stuck in a circle. It is frequently used in films and video games to build unending tension during suspenseful scenes.