But hearing can discern much more than just pitch and pace: it can pick up multiple instruments with differing timbres, keeping track of each note’s pitch, and even its attack and decay—how fast it rises and falls in volume. That is where another kind of sonification called parameter mapping comes in. This can turn scads of data sources into one stream of sound. The rise and fall of one variable is mapped to, say, the volume of a synthesised violin, while the shift of another is mapped to its pitch. Many different timbres of sound can be added, resulting in a data-rich soundscape.
Human hearing is extremely good at dealing with such noisy input. Making out what your interlocutor is saying at a crowded cocktail party, or noticing the approach of a predator among the cacophony of birds and bugs in a rainforest, can be done. “Where there are subtle changes of noise, or patterns in the change, that’s where the ear really takes over,” says Andy Hunt, of the University of York, in Britain.
