white noise

White Noise Machine from Yuri Suzuki on Vimeo.

"white noise"
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.

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It is used by some emergency vehicle sirens due to its ability to cut through background noise, which makes it easier to locate.

White noise is commonly used in the production of electronic music, usually either directly or as an input for a filter to create other types of noise signal. It is used extensively in audio synthesis, typically to recreate percussive instruments such as cymbals which have high noise content in their frequency domain.

It is also used to generate impulse responses. To set up the equalization (EQ) for a concert or other performance in a venue, a short burst of white or pink noise is sent through the PA system and monitored from various points in the venue so that the engineer can tell if the acoustics of the building naturally boost or cut any frequencies. The engineer can then adjust the overall equalization to ensure a balanced mix.

White noise is a common synthetic noise source used for sound masking by a tinnitus masker. White noise is a particularly good source signal for masking devices as it contains higher frequencies in equal volumes to lower ones, and so is capable of more effective masking for high pitched ringing tones most commonly perceived by tinnitus sufferers.

White noise is used as the basis of some random number generators. For example, Random.org uses a system of atmospheric antennae to generate random digit patterns from white noise.

White noise machines are sold as privacy enhancers and sleep aids and to mask tinnitus. Some people claim white noise, when used with headphones, can aid concentration by masking irritating or distracting noises in a person's environment.