Colors of noise

In <a href="/facts/Audio_engineering/eRJkg89Q">audio engineering</a>, <a href="/facts/Electronics/E4JhgISq">electronics</a>, <a href="/facts/Physics/a7aH2y08">physics</a>, and many other fields, the color of noise or noise spectrum refers to the <a href="/facts/Power_spectrum/q3Rfs7b0">power spectrum</a> of a <a href="/facts/Noise_(signal_processing)/JT3lGj8v">noise signal</a> (a signal produced by a <a href="/facts/Stochastic_process/Ng1n1dnB">stochastic process</a>). Different colors of noise have significantly different properties. For example, as <a href="/facts/Audio_signal/rFSTI9IF">audio signals</a> they will sound different to <a href="/facts/Hearing_(sense)/EPYrVkSx">human ears</a>, and as <a href="/facts/Digital_image/3TNT47Mv">images</a> they will have a visibly different <a href="/facts/Texture_(visual_arts)/U86nSEXm">texture</a>. Therefore, each application typically requires noise of a specific color. This sense of 'color' for noise signals is similar to the concept of <a href="/facts/Timbre/lVXB949E">timbre</a> in <a href="/facts/Music/hDVP0xsQ">music</a> (which is also called "tone color"; however, the latter is almost always used for <a href="/facts/Sound/DlKXlPuF">sound</a>, and may consider detailed features of the <a href="/facts/Spectrum/wPUjkpqI">spectrum</a>).
The practice of naming kinds of noise after colors started with <a href="/facts/White_noise/wJ0SR21n">white noise</a>, a signal whose spectrum has equal <a href="/facts/Power_(physics)/mkaEyRnn">power</a> 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. 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 β and hence they are examples of power-law noise. For instance, the spectral density of <a href="/facts/White_noise/wJ0SR21n">white noise</a> is flat (β = 0), while <a href="/facts/Flicker_noise/4uF4gWga">flicker</a> or <a href="/facts/Pink_noise/pUPduD35">pink noise</a> has β = 1, and <a href="/facts/Brownian_noise/YUtdwH4I">Brownian noise</a> has β = 2. <a href="/facts/Blue_noise/q2v4WmXe">Blue noise</a> has β = -1.

Colors of noise open-in-new

Colors of noise