Auditory illusion: the impossible sound

Published on August 26th, 2011
Auditory illusion: the impossible sound

You should have a listen to the Shepard scale, sound consisting of a superposition of sine waves separated by octaves.

So, your brain hears a seemingly impossible scale: one that constantly descends but doesn’t get any lower. How does this work?

The acoustical illusion can be constructed by creating a series of overlapping ascending or descending scales, similar to an optical illusion of the ever ascending staircase.

Have a listen to the sound here.

Do you think the trick in hearing this auditory illusion depends on the ear or the brain?

Pic credit: flickrized

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