Diana Deutsch developed some fascinating auditory illusions. These include the phenomenon of ‘speech to song’ whereby repeating loops of spoken word suddenly begin to sound like a song. In another illusion, ‘phantom words’ new words emerge from repeating fragments of words. To experience these all you need are headphones as the a stereo effect is essential, here is the link to her work.…

Speech to song http://deutsch.ucsd.edu/psychology/pages.php?i=212
Phantom Words http://deutsch.ucsd.edu/psychology/pages.php?i=211

A nice example of sine wave speech from Joe Banks [Disinformation] has written about psychoacoustics in his book https://rorschachaudio.com/  I was lucky to meet him at The Sensorium of Animals workshop.

“The McGurk effect” is a perceptual illusion that mixes a sound with the visual cue of a different sound, We see the mouth move and hear/see a mismatched sound, check out what happens… https://www.youtube.com/watch?v=aFPtc8BVdJk

This page has some great interactive examples of optical and sonic illusions
http://www.cs.ubc.ca/nest/imager/contributions/flinn/Illusions/Illusions.html