We hear certain background sounds even when they aren’t there – and studying why could help us understand to what extent our perceptual reality is just an illusion.

Josh McDermott and Richard McWalter at the Massachusetts Institute of Technology discovered this illusion while playing around with different sound effects.

You can hear one example in the video below. The audio starts with the sound of applause, which is then overlaid with a loud static sound. You should be able to hear applause in the background.