The Tritone paradox (try it with a group of musicians)

This is an interesting musical game for musicians to play, particularly in a group. Because of the balance of harmonics in the tones, the octave of their fundamental is ambiguous – they function like Shepard tones in this respect. Diana Deutsch has many more musical illusions on her site, but this is I think one of the most striking. Try it with someone else in the room and see if you agree with each other. I suspect age and possibly gender may affect the perceived octave.
http://deutsch.ucsd.edu/psychology/pages.php?i=206