Don’t believe everything you hear.
The video below is an auditory illusion known as the ‘Shepard tone’. Roger Shepard was a cognitive scientist who is said to be the “father of research on spatial relations”, and this trick is named after him because essentially what happens is a series of sine separated by an octave. That sounds really complicated, but I promise it really isn’t. Just give this video a play and then play it again and see what happens.
Did you notice that when you play it a second time it sounded like the scale got higher?
It might have sounded like it… but nope! The sequence didn’t change, just your perception of it. This occurs because the same note is playing at two octaves, but as the higher starting note descends it gets quieter and by the end of the clip it is virtually inaudible. Meanwhile, the lower octave note is gradually getting louder as it ascends and it becomes the loudest note you hear by the end of the clip. When those two sounds combine in sequence and you play it again it gives the illusion that it is continually ascending. Yada, yada, it’s essentially the equivalent of an audio barbershop pole.
If you liked that, check out some of these guided audio illusions from AsapScience. Totally worth it if you have headphones and some time on your hands.
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