The Shepard Tone

25 Apr

Hooray for bank holidays and the opportunity to write a quick blog post!

Here’s a peculiar audio illusion that I’ve come across a few times recently. In the following video, the tone continuously descends without getting any lower…

Very bizarre, non? Like a lift going down but never reaching the ground floor. This is the Shepard tone, discovered by the American psychologist, Roger Shepard.

The illusion is created by overlapping a series of looping descending tones, each one octave apart. By altering the respective volume of each tone during the loop, the individual tones fade in and out so that we cannot hear the beginning or end of the loop. Our brain therefore becomes all befuddled, hearing just one overall descending tone.

And the practical applications of such an auditory oddity? Well, not a lot really, apart from trying to prevent a little moustachioed Italian guy from finding his digital princess…

Another similar illusion is the Risset rhythm, where the beat sounds as if it’s constantly speeding up (or slowing down).


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