Audio Illusions: Just Your Ears Playing Tricks On You

What you hear is not always the truth. This is why you can't fully trust your ears because they can sometimes play tricks on you. These are called audio illusions. An episode of the AsapSCIENCE YouTube channel demonstrated three of the most common of these audio illusions - the McGurk Effect, the Tritone Paradox, and the Shepard Tone Illusion.

McGurk Effect - This is named after Harry McGurk who along with John MacDonald wrote a paper in 1976  titled Hearing Lips and Seeing Voices which first described the illusion. It's a perceptual phenomenon caused by the interaction between what you hear and what you see. Basically, the sound being made is similar but what you hear differs when the visual presentation of the source of the sound is altered. Here's a more in-depth demonstration of the McGurk Effect:

Tritone Paradox - First reported in 1986 by Diana Deutsch (a perceptual and cognitive psychologist), this auditory illusion is produced when a pair of Shepard tones separated by an interval of a tritone are sequentially played. People may hear the scales as either ascending or descending.

Shepard Tone Illusion - Also often described as a "sonic barber's pole", this auditory illusion is created by the superposition of sine waves separated by octaves. The tone continually descends or ascends in pitch but ultimately seems to get no lower or higher.