
Besides the well-known optical illusions there are acoustic ones, too. Perhaps the most popular acoustics illusion is the effect that was discovered by Shepard: A scale that gives the listener the impression of an endlessly rising melody - but in fact the pitch of the tones does not rise. This way it is possible to play musical pieces that would otherwise cross the human perception threshold.
Take the following example: You will hear a very simple melody which seems to rise. Sing with the sound and you will clearly realize that you will get off one octave higher than at the start. But - wait a moment! Replay the sound and verify that the last tone is exacly as high as the first! The illusion is perfect. If you do not believe it, then save the sound file and compare the fist and last tones directly, e.g. with a sound player or editor. read more











