White noise isn’t the only sonic hue—pink, blue, gray, and brown all affect listeners in different ways.
Most people are familiar with white noise, that static sound of an air conditioner that lulls us to sleep by drowning out any background noise.
Except technically, the whirl of a fan or hum of the AC isn’t white noise at all. Many of the sounds we associate with white noise are actually pink noise, or brown, or green, or blue. In audio engineering, there’s a whole rainbow of noise colors, each with its own unique properties, that are used to produce music, help relaxation, and describe natural rhythms like the human heartbeat. If you know what to look for, you can start to notice the colors of the noise that make up the soundscape around us.
If you decompose a sound wave, you can break it down into two fundamental characteristics: frequency, which is how fast the waveform is vibrating per second (one hertz is one vibration per second), and amplitude (sometimes measured as “power”), or the size of the waves. The noise types are named for a loose analogy to the colors of light: White noise, for example, contains all the audible frequencies, just like white light contains all the frequencies in the visible range.