An audio “illusion.” The pitch increases, and seems to continue when you replay the clip.
This phenomenon is known as Shepard’s paradox; the ending tones are the same as the beginning ones, so it’s the auditory equivalent of Escher’s “Ascending and Descending” perpetual staircase.
You can hear the same illusion (with an explanation) here: http://www.exploratorium.edu/exhibits/highest_note/
And a great Java visualization to help you understand the explanation here: http://www.netalive.org/tinkering/shepard-effect/
Awesome! Thanks!
That’s a really interesting phenomenon. I found the visualization to be less intuitive than it could have been (not to mention it contains several careless errors). Here’s my interpretation:
http://forums.howwhatwhy.com/files/317371-shepard_effect.PNG
Sorry that last link didn’t work. If you copy/paste the url you can see the image.