A random signal of every frequency in the audio spectrum, in which each higher octave drops off 3 dB. The lower octaves have more power, and the higher octaves have less power. Pink noise is generated to test loudspeakers in a room as well as to "tune" a room for best audio reproduction.

Also known as "1/f noise," pink noise patterns have been found in music melodies, semiconductors and atomic clocks. They are also found in nature, including the sounds of wind and waterfalls. Contrast with white noise and Gaussian noise.