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, sometimes pronounced as one over 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 approximated by the Bark scale, does not perceive equal magnitude at all frequencies, thus white noise is not perceived as white noise, while pink noise is.

Graphic equalizer s 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.

See also

• Noise (physics)
• Brown noise
• Statistics
• Audio signal processing
• Self-organised criticality
• Fractal

External links

• A Bibliography on 1/f Noise http://www.nslij-genetics.org/wli/1fnoise/
• DSP Generation of Pink (1/f) Noise http://www.firstpr.com.au/dsp/pink-noise/ - Detailed discussion of various algorithms, with code samples