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1/f noise

1/f noise is a signal or process with a frequency spectrum such that the spectral energy density is proportional to the reciprocal of the frequency. 1/f noise is also called pink noise or flicker noise.

In particular, there is equal energy in all octaves. In terms of power at a constant bandwidth, 1/f noise falls off at -3dB per octave.

1/f noise is found in a wide variety of physical phenomena. Examples include electronic devices, financial markets, astronomy, and human coordination.

The human auditory system, which uses a roughly logarithmic concept of frequency, perceives equal magnitude at all frequencies.

Graphic equalizers also divide signals into bands logarithmically and report power by octaves; audio engineers put pink noise through a system to test whether it has a flat frequency response in the useful spectrum.

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