What is white noise ?
White noise represents an important type of distribution of the contents over the spread of a spectrum. By spectrum, the entire canvass is meant here. It can be radio or say, any other electro-magnetic radiation. If the contents are populated uniformly over the range, it assumes significance. Applied to the visible spectrum a uniform distribution signifies the presence of all colours. The effect of all colours being equally present is known to be white (as for example demonstrated by the Newton's Disc). Random distribution also can typically contribute to a spectrum becoming white. Noise is a random phenomenon -- in most of the natural events including any electro-magnetic radiation.
White noise, particularly, has come to be associated as a random occurrence of all the possible contenders. White noise is thus a source for reference, test and some times an objective.A recent application of the unique property of the white noise is, inter alia, in the code division multiplexing where several communication channels are mapped such that the total distribution appears to be white, so effecting a more efficient utilisation of a rare commodity such as the e.m. spectrum.