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Signal noise
 
 
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In science
Science

In its broadest sense, science refers to any systematic knowledge or practice. In its more usual restricted sense, science refers to a system of acquiring knowledge based on scientific method, as well as to the organized body of knowledge gained through such research....
, and especially in physics
Physics

Physics is the natural science which examines basic concepts such as energy, force, and spacetime and all that derives from these, such as mass, charge, matter and its Motion ....
 and telecommunication
Telecommunication

Telecommunication is the assisted Transmission of Signal over a distance for the purpose of communication. In earlier times, this may have involved the use of smoke signals, Drum , Semaphore line, flag signals or heliograph....
, 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
Jamming

Jamming may mean:* Interfering with communications or surveillance:** Radio jamming** Radar jamming and deception** Mobile phone jammer** E-mail 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.






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Encyclopedia


In science
Science

In its broadest sense, science refers to any systematic knowledge or practice. In its more usual restricted sense, science refers to a system of acquiring knowledge based on scientific method, as well as to the organized body of knowledge gained through such research....
, and especially in physics
Physics

Physics is the natural science which examines basic concepts such as energy, force, and spacetime and all that derives from these, such as mass, charge, matter and its Motion ....
 and telecommunication
Telecommunication

Telecommunication is the assisted Transmission of Signal over a distance for the purpose of communication. In earlier times, this may have involved the use of smoke signals, Drum , Semaphore line, flag signals or heliograph....
, 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
Jamming

Jamming may mean:* Interfering with communications or surveillance:** Radio jamming** Radar jamming and deception** Mobile phone jammer** E-mail 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 in analog systems; however, digital systems are usually constructed in such a way that their quantized
Quantization (signal processing)

In digital signal processing, quantization is the process of approximating a continuous range of values by a relatively small set of discrete symbols or integer values....
 signals can be reconstructed perfectly, as long as the noise level remains below a defined maximum, which varies from application to application.

More specifically, in physics, the term noise has the following meanings:
  1. An undesired disturbance within the frequency
    Frequency

    Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency....
     band
    Band (radio)

    A band is a small section of the electromagnetic spectrum of radio communication frequency, in which channel are usually used or set aside for the same purpose....
     of interest; the summation of unwanted or disturbing energy introduced into a communications system
    Communications system

    In telecommunication, a communications system is a collection of individual information transfer networks, transmission systems, relay stations, tributary stations, and data terminal equipment usually capable of interconnection and interoperation to form an integrated whole....
     from man-made and natural sources.
  2. A disturbance that affects a signal and that may distort the information
    Information

    Information as a Conveyed concept has a diversity of meanings, from everyday usage to technical settings. Generally speaking, the concept of information is closely related to notions of constraint, communication, control system, data, form, instruction, knowledge, Meaning , stimulation, pattern, perception, and knowledge representation....
     carried by the signal.
  3. Random variations of one or more characteristics of any entity such as voltage, current, or data
    DATA

    Debt, AIDS, Trade in Africa is a multinational Non-governmental organization founded in January 2002 in London by U2's Bono along with Robert Sargent Shriver III and activists from the Jubilee 2000 Drop the Debt campaign....
    .
  4. A random signal of known statistical properties of amplitude, distribution, and spectral density
    Spectral density

    In statistical signal processing and physics, the spectral density, power spectral density , or energy spectral density , is a positive real function of a frequency variable associated with a stationary stochastic process, or a deterministic function of time, which has dimensions of power per Hz, or energy per Hz....
    .
  5. 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. Claude Shannon established information theory
Information theory

Information theory is a branch of applied mathematics and electrical engineering involving the quantification of information. Historically, information theory was developed by Claude E....
 and in so doing clarified the essential nature of noise and the limits it places on the operation of electronic equipment.

In some cases a little noise may be considered advantageous, allowing a dither
Dither

Dither is an intentionally applied form of noise, used to randomize quantization error, thereby preventing large-scale patterns such as contouring that are more objectionable than uncorrelated noise....
ed representation of signals below the minimum strength, or between two quantization levels. This is especially true for signals intended for human appreciation, since the brain seems to expect signals to contain a degree of "neural noise", or the phenomenon of stochastic resonance
Stochastic resonance

Stochastic resonance is observed when noise added to a system improves the system's performance in some fashion. More technically, SR occurs if the signal-to-noise ratio of a nonlinear system or device increases for moderate values of noise intensity....
, where small amount of noise improves the detection of signals in non-linear sensors.

See also


  • Electronic noise
    Electronic noise

    Electronic noise is an unwanted signal characteristic of all electronics electrical circuit. Depending on the circuit, the noise put out by electronic devices can vary greatly....
  • Colors of noise
    Colors of noise

    Even though noise is a Randomness Signal , it can have characteristic statistical properties. Spectral density is such a property, which can be used to distinguish different types of noise....
  • Signal-to-noise ratio
    Signal-to-noise ratio

    Signal-to-noise ratio is an electrical engineering measurement, also used in other fields , defined as the ratio of a signal power to the noise power corrupting the signal....
  • Electromagnetic interference
    Electromagnetic interference

    Electromagnetic interference is an unwanted disturbance that affects an electrical circuit due to either electromagnetic conduction or electromagnetic radiation emitted from an external source....
  • Noise level
    Noise level

    In telecommunication, noise level is the noise power, usually relative to a reference.In atmospheric sound transmission, noise level is the noise power of the longitudinal sound wave relative to a point of reference....
  • Noise power
    Noise power

    In telecommunication, the term noise power has the following meanings:# The measured total noise per Bandwidth unit at the input or output of a device when the signal is not present....
  • Noise-equivalent power
    Noise-equivalent power

    Noise-equivalent power is a measure of the sensitivity of an optical detector or detector system. It is defined as the signal power which gives a signal to noise ratio of 1 for an integration time of half a second, or more technically the radiant power that produces a signal to noise ratio of unity at the output of a given optical detector a...
  • Phase noise
    Phase noise

    Phase noise is the frequency domain representation of rapid, short-term, random fluctuations in the phase of a wave, caused by time domain instabilities ....
  • List of noise topics
    List of noise topics

    This is a list of noise topics....
  • Audio system measurements
    Audio system measurements

    Audio system measurements are made for several purposes. Designers take measurements so that they can specify the performance of a piece of equipment....
  • Stochastic resonance
    Stochastic resonance

    Stochastic resonance is observed when noise added to a system improves the system's performance in some fashion. More technically, SR occurs if the signal-to-noise ratio of a nonlinear system or device increases for moderate values of noise intensity....


External links

  • (PDF) — Analog Devices
    Analog Devices

    Analog Devices is an United States Multinational corporation producer of semiconductor devices. Analog specializes in analog-to-digital converter, digital-to-analog converter, MEMS, and digital signal processing chips for consumer and industrial goods....
     Application note