In color theory, brightness (value) defines how light or dark a particular hue can be.

Similarly in music, brightness correlates to how loud or quiet a sound can be. Louder sounds can be interpreted as brighter and quieter sounds can be interpreted as darker.

Interestingly, people tend to perceive higher frequency pitches to be louder than lower frequency pitches of the same volume. A low frequency pitch would have to be louder in order to produce the same level of auditory brightness.

This audiovisual exhibit demonstrates the asymmetrical sensitivities of auditory brightness across the frequency spectrum through corresponding changes in optical brightness.