Noise is caused by randomly generated amplitude across the sound frequency spectrum.


White noise: Equal energy per frequency


Pink noise: Equal energy per octave

Pink noise is useful for tuning sound systems in new acoustic environments.


For example if a concert sound system is installed at the Melbourne Town Hall the audio engineer may play pink noise through the speakers and using a reference mic, frequency analyser and equaliser, tune the system back to a flat frequency response to help compensate for the natural frequency response of the hall.