White Noise

A sound or signal consisting of all audible frequencies with equal intensity. The term is used analogously to the term 'white light' in optics which denotes the simultaneous presence of colours of all frequencies.

Bands of filtered white noise are sometimes referred to as coloured noise, but the analogy to colour has not been applied systematically to sound. The term pink noise refers to a kind of noise where each octave band has the same intensity, and therefore does not sound as bright as white noise since the intensity of the spectrum does not increase with higher frequencies.

Compare: Background Noise, Broad Band Noise, Gaussian Noise, Hiss, Narrow Band Noise, Random Noise, Rumble, Rustle Noise, Stochastic Process.

A pure white noise signal may only be produced by a generator called a white noise generator and is often used as a sound source in sound synthesis. However, many sounds in nature and industry resemble white or coloured noise, such as water, wind, ventilation noise, or sibilance such as 'ch' or 'sh'.

Because of its broad-band spectrum, white noise has strong masking abilities.

Third-octave spectrum of a white noise generator showing the characteristic increase of energy with frequency. By contrast, the nearly flat spectrum of the Athabaska River in Alberta is shown at right for comparison.