Editing Pink noise (section)

== Description ==
[[File:Pink noise spectrum.svg|thumb|left|Spectrum of a pink noise approximation on a log-log plot; power density falls off at 10&nbsp;dB/decade of frequency]]
[[File:Noise.jpg|thumb|left|Relative intensity of pink noise (left) and [[white noise]] (right) on an [[fast Fourier transform|FFT]] [[spectrogram]] with the vertical axis being linear frequency]]

In pink noise, there is equal energy per [[octave]] of frequency. The energy of pink noise at each frequency level, however, falls off at roughly 3&nbsp;[[decibels|dB]] per octave. This is in contrast to [[white noise]] which has equal energy at all frequency levels.<ref>{{Cite web |title=Noise |url=https://www.sfu.ca/~gotfrit/ZAP_Sept.3_99/n/noise.html |access-date=2024-02-06 |website=www.sfu.ca}}</ref>

The [[human auditory system]], which processes frequencies in a roughly logarithmic fashion approximated by the [[Bark scale]], does not perceive different frequencies with equal sensitivity; signals around 1–4&nbsp;kHz sound [[loudness|loudest]] for a given intensity. However, humans still differentiate between white noise and pink noise with ease.

[[Graphic equalizer]]s also divide signals into bands logarithmically and report power by octaves; audio engineers put pink noise through a system to test whether it has a flat frequency response in the spectrum of interest. Systems that do not have a flat response can be equalized by creating an inverse filter using a graphic equalizer. Because pink noise tends to occur in natural physical systems, it is often useful in audio production. Pink noise can be processed, filtered, and/or effects can be added to produce desired sounds. Pink-noise generators are commercially available.

One parameter of noise, the peak versus average energy contents, or [[crest factor]], is important for testing purposes, such as for [[audio power amplifier]] and [[loudspeaker]] capabilities because the signal power is a direct function of the crest factor. Various crest factors of pink noise can be used in simulations of various levels of [[dynamic range compression]] in music signals. On some digital pink-noise generators the crest factor can be specified.