I thought I had a pretty good idea of the limitations of human hearing from working on recordings in the studio, spending hours listening to minor changes in sound frequencies. When you speak to the average person on the street, they don’t care if they’re listening to a 128kbits or 320 kbits mp3, or a vinyl LP. I never realised that our hearing doesn’t just depend on what we take in aurally, but also on what we’re seeing – at least in a speech perception sense.

This article on the Scientific American website has spun me out. It illustrates an auditory illusion called the (awesomely named) McGurk effect, where if you listen to a particular phoneme being spoken, combined with video of someone speaking a second phoneme, you wind up thinking you heard a third totally different phoneme. Even if you know it’s happening, it’s impossible to make yourself hear the correct sound. It even can work across entire sentences.

I’m struggling to think of an application for this kind of thing, but one possible example would be if you were trying to get someone to agree to something in a recorded verbal conversation, and structured a sentence so that they perceived you as saying one thing but the recording picked up something else, you may be able to secure the desired response in a way that creates a misleading impression of the person’s intent.

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