If the phoneme is replaced by a period of silence, rather than a cough, the deletion is very obvious.

But not only do most people hear the complete sentence, they generally find it very difficult to work out which phoneme has been deleted. One of the phonemes has actually been completely removed by the cough. In this recording by Richard Warren from the University of Wisconsin in Milwaukee, a spoken sentence is interrupted by a cough. This means that if a part of an audio recording is missing, our brains will often work out what should have been there. Much of human perception is the result of the brain filling in gaps in the data from our senses. Indeed, you may find that the phrases you hear are related to what’s on your mind – for example, people who are dieting often hear phrases associated with food. Your brain is constructing them, in a bid to make sense of a meaningless noise. However, none of the phrases are really there. As you listen to it, you’ll start to pick out specific phrases. Building on the stereo effect described above, the recording features overlapping sequences of repeating words or phrases, located in different regions of stereo space. This illusion was first demonstrated by Diana Deutsch at the University of California, San Diego. The illusion demonstrates our ability to locate sounds in space by comparing the inputs to the two ears, we can work out where a sound is coming from.Ģ Phantom words (Listen through stereo separated loudspeakers, best placed some distance apart) Similarly, increases in the volume of sound from the clippers give the impression that he is bringing them closer and closer to each ear. As the barber “moves” to your right, the volume increases slightly in the right channel and decreases in the left. Listening to it, you feel as though you are in a barber’s chair, with the barber moving around you, clipping away at your hair.

This is a demonstration of the stereo effect. 1 Barber’s shop illusion (Listen with headphones)

Auditory illusions holophonic sound