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noise (N)

Noise is a statistically distributed fluctuation of a physical quantity caused by stochastic processes. Inelectronics, these stochastic processes are generated by the current flow in active and passive components. These are uncoordinated temperature-induced movements of charge carriers in electrically conductive materials.

Noise presents itself as a signal that cannot be assigned to a frequency, wavelength, phase or amplitude. The spectral distribution is frequency-dependent. Noise is essentially determined by the distribution of the noise energy over the bandwidth and is designated by colors. If the noise energy is constant over a frequency band, it is called white noise, and the noise density is independent of frequency. If there is no noise energy, it is black noise.

Noise types and their frequency energy density

Noise types and their frequency energy density

Noise whose spectral power density differs from that of white noise is called colored noise and is assigned certain colors depending on its frequency dependence. Colored noise, which is not exactly specified, is characterized by the fact that the noise energy has a disproportionate or disproportionate frequency dependence. Colors are assigned to these noise types: white noise, red noise, blue noise, violet noise, pink noise and black noise. Furthermore, orange noise, green noise and gray noise are known. The Federal Standard 1037C Telecommunications defines white noise, black noise, pink noise and blue noise.

Noise displayed on an oscilloscope

Noise displayed on an oscilloscope

Since noise depends on bandwidth, it affects the useful signal. The ratio of useful signal to noise signal is called signal-to-noise ratio( SNR).

A measure of the noise temperature measured in satellite reception systems is the Kelvin.

Informations:
Englisch: noise - N
Updated at: 30.01.2014
#Words: 257
Links: current, active, signal, frequency (f), phase
Translations: DE
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