Timbre

The perceived quality or 'colour' of a sound that distinguishes different sources playing the same pitch and loudness — for instance, the difference between a flute, a violin, and a human voice singing the same note. Timbre is determined largely by the spectral content (the fundamental frequency plus overtones), the attack envelope, and how these evolve over time. In auditory display and sonification, timbre is a valuable dimension for encoding categorical or ordinal data, but designers must account for the fact that timbre perception is not independent of pitch or loudness. Timbre also matters for accessibility of audio interfaces: distinct timbres help users separate overlapping audio streams and identify the source of notifications.