Sound quality having a harsh or brittle high-end with too much focus on the upper frequencies. Bright sounding audio equipment gets your attention but can be fatiguing to listen to over long periods of time. Think of a screeching like the screeching of bad brakes or fingernails on a blackboard. These are bright sounds. Most audio equipment does not exhibit that extreme level of brightness, but an overly bright sound is not proper and is essentially a form of distortion (unless the source material is very bright with a lot of energy in the high frequencies in which case an audio system may simply be faithfully reproducing a poor recording).