Pink noise
From Freepedia
Pink noise, also known as 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. Sometimes pronounced as one over f noise, it is also called flicker noise.
There is equal energy in all octaves. In terms of power at a constant bandwidth, 1/f noise falls off at 3 dB per octave.
The human auditory system, which uses a roughly logarithmic concept of frequency approximated by the Bark scale, does not perceive with equal sensitivity all audible frequencies. However, humans may still differentiate between white noise and pink noise with ease.
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.
From a practical point of view, producing true pink noise is impossible, since the energy of such a signal would be infinite. That is, the energy of pink noise in any frequency interval from <math>f_1</math> to <math>f_2</math> is proportional to <math>\log(f_2/f_1)</math> and if <math>f_2</math> is infinity, so is the energy. Practically, pink noise is only pink over a certain frequency interval. The same is true of white noise which is usually used to produce pink noise by filtering to remove more and more energy at succesively higher frequencies (about 3 dB per octave).
| Image:Gnome-speakernotes.png | Pink noise (info) |
| 10 seconds of pink noise | |
| Problems listening to the file? See media help. |
See also
- White noise
- Noise (physics)
- Brown noise
- Statistics
- Audio signal processing
- Self-organised criticality
- Fractal
- Colors of noise
External links
- A Bibliography on 1/f Noise
- DSP Generation of Pink (1/f) Noise - Detailed discussion of various algorithms, with code samples
- Noise - an open-source program that creates pink noise on the Macintosh
