Auditory Illusions: A Tour of Tricky Sounds
Auditory illusions are sounds that trick us. We all mishear things at times, but well-crafted illusions are persistently deceptive. On this podcast, we string together some great illusions. As you will hear, they reveal aspects of our brains’ workings that are usually invisible.
In trawling the net, we came across many sound illusion lists. Our favorites are at Listverse, New Scientist, Jaxov, Scientific American. This site has quite a few boring so-called illusions, but we do recommend the “melody of silences.” A listener suggested a really cool example of infinitely increasing tempo. If there is a rock-star of auditory illusions, it is Diana Deutsch, who has many samples on her site. Wikipedia is also a great source, and we recommend its articles on sound localization, binaural recording, and Shepard tones.
In the podcast we mention the falling bells illusion, which makes more sense with the image below. It is a spectrogram, showing frequency (pitch) on the y-axis and time on the x-axis. Each tone looks like a downward-curving band, and each new band is shifted up.
One of the best sound illusions requires video. It shows that what we see can override what we hear. If you have not seen the McGurk Illusion yet, you really should watch this!
In the podcast, we promise a video of an undersea creature. Enjoy:
If you watched the video to the end, you heard that the octopus is not perfectly matched to its surroundings; it is just similar enough that our brain does not detect it.
The brain has to interpret complicated and ambiguous data from our senses, and because of evolution it usually does a good job simulating the world. But our perceptions are always incomplete guesses. That is why other humans and other animals do not perceive things quite as you do; that is also why, in the case of illusions, our brain can be stubbornly wrong.
Nigel Moore found much of the audio and contributed research to this podcast.