**White noise** is a random signal or process with a flat power spectral density. In other words, the signal contains equal power within a fixed bandwidth at any center frequency. White noise draws its name from white light in which the power spectral density of the light is distributed over the visible band in such a way that the eye's three color receptors (cones) are approximately equally stimulated.

In statistical sense, a time series r_{t} is characterized as having weak white noise if {r_{t}} is a sequence of serially uncorrelated random variables with zero mean and finite variance. Strong white noise also has the quality of being independent and identically distributed, which implies no autocorrelation. In particular, if r_{t} is normally distributed with mean zero and standard deviation σ, the series is called a Gaussian white noise.

An infinite-bandwidth white noise signal is a purely theoretical construction. The bandwidth of white noise is limited in practice by the mechanism of noise generation, by the transmission medium and by finite observation capabilities. A random signal is considered "white noise" if it is observed to have a flat spectrum over a medium's widest possible bandwidth.

Read more about White Noise: White Noise in A Spatial Context, Statistical Properties, Applications, Random Vector Transformations, Random Signal Transformations, Generation

### Famous quotes containing the words white and/or noise:

“The better a work is, the more it attracts criticism; it is like the fleas who rush to jump on *white* linens.”

—Gustave Flaubert (1821–1880)

“And its *noise* as the *noise* in a dream; and its depth as the roots

of the sea:”

—A.C. (Algernon Charles)