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Noise Colours & Types

Certain noises are described by their colour, for example, the term "white noise" is common in audio production and other situations. Some of these names are official and technical, others have more loose definitions. These terms generally refer to random noise which may contain a bias towards a certain range of frequencies.

Black Noise A term with numerous conflicting definitions, but most commonly refers to silence with occasional spikes.
Blue Noise Contains more energy as the frequency increases.
Brown Noise Mimics the signal noise produced by brownian motion.
Gray Noise Similar to white noise, but has been filtered to make the sound level appear constant at all frequencies to the human ear.
Green Noise An unofficial term which can mean the mid-frequencies of white noise, or the "background noise of the world".
Orange Noise An unofficial term describing noise which has been stripped of harmonious frequencies.
Pink Noise Contains an equal sound pressure level in each octave band. Energy decreases as frequency increases.
Purple Noise Contains more energy as the frequency increases.
Red Noise An oceanographic term which describes ambient underwater noise from distant sources. Also another name for brown noise.
White Noise Contains an equal amount of energy in all frequency bands.

Note: Some of these definitions refer to "all frequencies". This is only theoretical — in practice this means "all frequencies in a finite range".

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