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In science, and especially in physics and telecommunication, noise is fluctuations in and the addition of external factors to the stream of target information ( signal) being received at a detector. In communications, it may be deliberate as for instance jamming of a radio or TV signal, but in most cases it is assumed to be merely undesired interference with intended operations. Natural and deliberate noise sources can provide both or either of random interference or patterned interference. Only the latter can be cancelled effectively. More specifically, in physics, the term noise has the following meanings:
- An undesired disturbance within the frequency band of interest; the summation of unwanted or disturbing energy introduced into a communications system from man-made and natural sources.
- A disturbance that affects a signal and that may distort the information carried by the signal.
- Random variations of one or more characteristics of any entity such as voltage, current, or data.
- A random signal of known statistical properties of amplitude, distribution, and spectral density.
- Loosely, any disturbance tending to interfere with the normal operation of a device or system.
Noise and what can be done about it has long been studied. It was Shannon who established information theory and in so doing clarified the essential nature of noise and the limits it places on operation of our (or anyone's) equipment. Shannon's work was a breakthrough.
Some sections copied from Federal Standard 1037CFederal Standard 1037C entitled Telecommunications: Glossary of Telecommunication Terms is a U. Federal Standard, issued by the General Services Administration pursuant to the Federal Property and Administrative Services Act of 1949, as amended. This docu and from MIL-STD-188MIL-STD-188 is a series of U. military standards relating to telecommunications. Documents 100 Common Long Haul and Tactical Communication System Technical Standards. 105 Interoperability and Performance Standards for the All Digital Tactical-To-Strategic
See also
- shot noiseShot noise consists of random fluctuations of the electric current in an electrical conductor, which are caused by the fact that the current is carried by discrete charges ( electrons). The strength of this noise increases for growing magnitude of the ave
- 1/f noiseSignal processing Digital signal processing 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 ca
- white noiseThis article is about white noise as a scientific concept, see also White Noise as a 1985 novel by Don DeLillo. White Noise (movie) as a 2004 movie by Geoffrey Sax. White noise is a signal (or process) with a flat frequency spectrum. In other words, the s
- Johnson-Nyquist noiseJohnson-Nyquist noise (sometimes only "Nyquist noise") is the equilibrium fluctuations of the electric current inside an electrical conductor, which happens without any applied voltage, due to the random thermal motion of the charge carriers (the electron
- signal-to-noise ratioThe phrase signal-to-noise ratio often abbreviated SNR or S/N is an engineering term for the ratio between the magnitude of a signal (meaningful information) and the magnitude of background noise. Because many signals have a very wide dynamic range, SNRs
- noise levelIn telecommunication, noise level is the noise power, usually relative to a reference. Note Noise level is usually measured in dB for relative power or picowatts for absolute power. A suffix is added to denote a particular reference base or specific quali
- noise power
- noise-equivalent power
- phase noise
- thermal noise
- list of noise topics
- Audio system measurements
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