On: A Sound You Can't Unhear (And What It Says About Y...

[gwern]

Here's some more: http://www.lifesci.sussex.ac.uk/home/Chris_Darwin/SWS/

Apparently this is called 'sine-wave speech' and is an example of 'perceptual set' (http://www.simplypsychology.org/perceptual-set.html)