Editing Colors of noise (section)

{{Short description|Power spectrum of a noise signal}}
{{Redirect|Black noise|other uses|Black Noise (disambiguation){{!}}Black Noise}}
{{Confusing|date=December 2021}}
{{Use dmy dates|date=October 2023}}
[[File:The Colors of Noise.svg|thumb|right|Simulated power spectral densities as a function of frequency for various colors of noise (violet, blue, white, pink, Brown/red).
The power spectral densities are arbitrarily normalized such that the value of the spectra are approximately equivalent near 1&nbsp;kHz.
Note the slope of the power spectral density for each spectrum provides the context for the respective electromagnetic/color analogy.]]
{{Colors of noise}}

In [[audio engineering]], [[electronics]], [[physics]], and many other fields, the '''color of noise''' or '''noise spectrum''' refers to the [[power spectrum]] of a [[noise (signal processing)|noise signal]] (a signal produced by a [[stochastic process]]). Different colors of noise have significantly different properties. For example, as [[audio signal]]s they will sound different to [[hearing (sense)|human ears]], and as [[digital image|images]] they will have a visibly different [[texture (visual arts)|texture]]. Therefore, each application typically requires noise of a specific color. This sense of 'color' for noise signals is similar to the concept of [[timbre]] in [[music]] (which is also called "tone color"; however, the latter is almost always used for [[sound]], and may consider detailed features of the [[spectrum]]).

The practice of naming kinds of noise after colors started with [[white noise]], a signal whose spectrum has equal [[power (physics)|power]] within any equal interval of frequencies.  That name was given by analogy with white light, which was (incorrectly) assumed to have such a flat power spectrum over the visible range.{{Citation needed|date=April 2015}} Other color names, such as ''pink'', ''red'', and ''blue'' were then given to noise with other spectral profiles, often (but not always) in reference to the color of light with similar spectra. Some of those names have standard definitions in certain disciplines, while others are informal and poorly defined. Many of these definitions assume a signal with components at all frequencies, with a power spectral density per unit of bandwidth proportional to 1/''f''&nbsp;<sup>''β''</sup> and hence they are examples of ''power-law noise''.  For instance, the spectral density of [[white noise]] is flat (''β'' = 0), while [[flicker noise|flicker]] or [[pink noise]] has ''β'' = 1, and [[Brownian noise]] has ''β'' = 2. [[Blue noise]] has ''β'' = -1.