Pink Noise - Occurrence

Occurrence

1/ƒ noise occurs in many physical, biological and economic systems. Some researchers describe it as being ubiquitous. In physical systems, it is present in some meteorological data series, the electromagnetic radiation output of some astronomical bodies, and in almost all electronic devices (referred to as flicker noise). In biological systems, it is present in heart beat rhythms, neural activity, and the statistics of DNA sequences. In financial systems, it is often referred to as a long-term memory effect. Also, it describes the statistical structure of many natural images (images from the natural environment). Recently, 1/f noise has also been successfully applied to the modeling of mental states in psychology.

Richard F. Voss and J. Clarke claim that almost all musical melodies, when each successive note is plotted on a scale of pitches, will tend towards a pink noise spectrum. Similarly, a generally 1/f distribution pattern has been observed in film shot length by researcher James E. Cutting of Cornell University, in the study of 150 popular movies released from 1935 to 2005.

Although self-organised criticality has been able to reproduce 1/f noise in sandpile models, there are no simple mathematical models to create pink noise. It is usually generated by filtering white noise.

There are many theories of the origin of 1/ƒ noise. Some theories attempt to be universal, while others are applicable to only a certain type of material, such as semiconductors. Universal theories of 1/ƒ noise remain a matter of current research interest.