In electronics, noise is a random fluctuation in an electrical signal, a characteristic of all electronic circuits. Noise generated by electronic devices varies greatly, as it can be produced by several different effects. Thermal noise is unavoidable at non-zero temperature (see fluctuation-dissipation theorem), while other types depend mostly on device type (such as shot noise, which needs steep potential barrier) or manufacturing quality and semiconductor defects, such as conductance fluctuations, including 1/f noise.
In communication systems, the noise is an error or undesired random disturbance of a useful information signal, introduced before or after the detector and decoder. The noise is a summation of unwanted or disturbing energy from natural and sometimes man-made sources. Noise is, however, typically distinguished from interference, (e.g. cross-talk, deliberate jamming or other unwanted electromagnetic interference from specific transmitters), for example in the signal-to-noise ratio (SNR), signal-to-interference ratio (SIR) and signal-to-noise plus interference ratio (SNIR) measures. Noise is also typically distinguished from distortion, which is an unwanted alteration of the signal waveform, for example in the signal-to-noise and distortion ratio (SINAD). In a carrier-modulated passband analog communication system, a certain carrier-to-noise ratio (CNR) at the radio receiver input would result in a certain signal-to-noise ratio in the detected message signal. In a digital communications system, a certain Eb/N0 (normalized signal-to-noise ratio) would result in a certain bit error rate (BER).
While noise is generally unwanted, it can serve a useful purpose in some applications, such as random number generation or dithering.
Other articles related to "noise":
... Generation–recombination noiseMatched filter for noisereduction in modems Noisereduction and noisecancellation for audio and images Error correction for digital signals subject to noise ... Phonon noise ...
Famous quotes containing the word noise:
“You may say a cat uses good grammar. Well, a cat doesbut you let a cat get excited once; you let a cat get to pulling fur with another cat on a shed, nights, and youll hear grammar that will give you the lockjaw. Ignorant people think its the noise which fighting cats make that is so aggravating, but it aint so; its the sickening grammar they use.”
—Mark Twain [Samuel Langhorne Clemens] (18351910)