Hearing the Escher staircase

Escher staircaseYou know this staircase, right?

In class, we heard the auditory analog of this visual illusion: the “Shepard-Risset glissando”, named after the two guys who worked on it. [sound sample]

The trick here is that the sound contains four notes all an octave apart, with the loudness of each note sneakily adjusted as the pitch of the notes climbs.

To understand this trick better, here’s a good visualization and demo of the discrete Shepard scale:
Visualization of the Shepard Effect

Much more discussion of how it all works on the Shepard tone Wikipedia page, which includes another sound sample of the glissando…

An independently discovered version of the Shepard tone appears at the beginning and end of the 1976 album A Day At The Races by the band Queen. The piece consists of a number of electric-guitar parts following each other up a scale in harmony, with the notes at the top of the scale fading out as new ones fade in at the bottom. Lose Control by Missy Elliott also seems to feature an ascending Shepard tone as a recurring theme (via the sampled synthesizers from Cybotron’s song “Clear”.) “Echoes”, a 23-minute song by Pink Floyd, concludes with a rising Shepard tone.

April 9, 2007. academics, sound. No Comments.

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