Editing Pink noise (section)

{{Short description|Signal with equal energy per octave}}
{{about||the album by Laura Mvula|Pink Noise (album)}}
{{About|1/f noise|quantum 1/f noise|quantum 1/f noise}}{{Redirect|Fractal noise|the novel|Fractal Noise}}
{{Listen
 | filename    = Pink noise.ogg
 | title       = Pink noise
 | description = 10 seconds of pink noise, [[audio normalization|normalized]] to −1 [[dBFS]] [[peak amplitude]]
 | type        = sound
}}
[[File:2D pink noise.png|thumb|upright|A two-dimensional pink noise [[grayscale]] image, generated with a computer program; some fields observed in nature are characterized by a similar power spectrum<ref name="Field-1987"/>]]
[[File:Pink noise cube.gif|thumb|upright|A 3D pink noise image, generated with a computer program, viewed as an animation in which each frame is a 2D slice]]
{{Colors of noise}}

'''Pink noise''', '''{{frac|1|f}} noise''', '''fractional noise''' or '''fractal noise''' is a [[signal (information theory)|signal]] or process with a [[frequency spectrum]] such that the [[power spectral density]] (power per frequency interval) is [[inversely proportional]] to the [[frequency]] of the signal. In pink noise, each [[Octave (electronics)|octave]] interval (halving or doubling in frequency) carries an equal amount of noise energy.

Pink noise sounds like a [[waterfall]].<ref>{{cite web |url=https://www.soundonsound.com/glossary/pink-noise |title=Glossary: Pink Noise |website=[[Sound on Sound]] |access-date=November 22, 2022}}</ref> It is often used to tune [[loudspeaker]] systems in [[professional audio]].<ref name=Sound>{{cite book |last1=Davis |first1=Gary |last2=Jones |first2=Ralph |date=1987 |title=The Sound Reinforcement Handbook |publisher=Hal Leonard |page=107 |isbn=0-88188-900-8}}</ref> Pink noise is one of the most commonly observed signals in biological systems.<ref>{{cite journal |last1=Szendro |first1=P |title=Pink-Noise Behaviour of Biosystems |journal=European Biophysics Journal |date=2001 |volume=30 |issue=3 |pages=227–231 |doi=10.1007/s002490100143 |pmid=11508842 |s2cid=24505215 |url=https://www.tandfonline.com/doi/abs/10.1081/JBC-100104145|url-access=subscription }}</ref>

The name arises from the pink appearance of visible light with this power spectrum.<ref name="Downey-2012">{{cite book|last=Downey|first=Allen|title=Think Complexity|year=2012|publisher=O'Reilly Media|isbn=978-1-4493-1463-7|pages=79|url=http://greenteapress.com/complexity/html/thinkcomplexity010.html#toc57|quote=Visible light with this power spectrum looks pink, hence the name.}}</ref> This is in contrast with [[white noise]] which has equal intensity per frequency interval.