Most naive listeners hear this as a set of simultaneous whistles, or science fiction sounds. However, for listeners that have previously heard this sound: Listening to the sine-wave speech sound again produces a very different percept of a fully intelligible spoken sentence. This dramatic change in perception is an example of "perceptual insight" or pop-out. We have argued that this form of pop-out is an example of a top-down perceptual process produced by higher-level knowledge and expectations concerning sounds that can potentially be heard as speech.Here's one example: Sine Wave Speech | Clear Speech
It's almost, but not quite, as weird as the McCollough Effect optical illusion that lasts 24 hours or longer.
More here: Clear Speech
(Via Mind Hacks)
Mark Frauenfelder is the founder of Boing Boing and the editor-in-chief of MAKE and Cool Tools. Twitter: @frauenfelder. His new book is Maker Dad: Lunch Box Guitars, Antigravity Jars, and 22 Other Incredibly Cool Father-Daughter DIY Projects