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Auditory streaming examples

In order to make sense of the world around us, our auditory system has to separate out the mixture of sounds that arrives at the ears into distinct sources or objects (e.g. multiple voices, music, background noise). This is not a straightforward process, but it works well and we are generally unaware of it happening! However, there are often multiple ways of interpreting the same set of sounds and in these instances we may notice our perception change. Have a listen to the following repeated pattern of tones. You should find that the timing between the tones gives rise to a galloping rhythm.

Demo 1

When one tone is much higher than the other, the galloping rhythm can disappear. In the next example, you will probably hear two separate sequences of regularly repeating tones at the same time - one high and one low.

Demo 2

Other sequences are more ambiguous. You may be able to hear the following example as a single galloping rhythm, or as two separate sequences. Your perception may change as you continue to listen, even though the tone pattern itself remains fixed.

Demo 3

When there are tones of three different frequencies, things can get even more complicated! Try hearing this sequence as one pattern, then focus in on one or other of the repeated tones. What happens to the tones you are not focused on? Can you hear three separate sequences at the same time?

Demo 4

Finally, these perceptual switches don't only occur for tones. Speech can behave strangely too. After a while, the "s" sounds at the beginning of each of the following syllables ("stone") can break away from the rest of the word. When this happens, they form a separate perceptual stream from the remaining "dohne" sounds.

Demo 5

By investigating the way that listeners perceive ambiguous patterns, we aim to learn how the brain makes sense of the chaotic auditory world around us.

If you have not already done so, why not click here to find out how the brain fills in gaps in sound?

This material was brought to you by Alex Billig and Bob Carlyon of the MRC Cognition and Brain Sciences Unit, Cambridge, UK.