Sounds like a good illusion

We all know optical illusions are meant to fool our senses. Straight lines look curved, big circles look smaller. Illusions of this type happen when our brains make the wrong assumptions.

Each of our senses has a really tough job to do, and most of the time we get it right, but occasionally researchers can create particular patterns that cause our brains to make mistakes, to try and measure something that's not quite as we expect. Hearing is a human sense too and our brain also makes assumptions about what it expects to hear. There are lots of fascinating audio illusions that we can create which fool our hearing.

Sound illusions are more of a problem to demonstrate than visual illusions. Unlike when we try and fool the eye, we can't print them for you to look at - you need to hear them. The link below takes you to some fascination audio illusions, illusions that work because they fool the way our brains process audio information. Researchers like illusions, because although it's often easy to try and get a computer program to get things right, if you can create a computer program that gets things wrong in the same way as a human does then that's good evidence your program has found something fundamental about the way our senses work. Illusions can also have real applications, for example as secret ringtones only teenagers can hear. You'll see what we mean.