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Encyclopedia > Noise

In common use the word noise means unwanted sound or noise pollution. In electronics noise can refer to the electronic signal corresponding to acoustic noise (in an audio system) or the electronic signal corresponding to the (visual) noise commonly seen as 'snow' on a degraded television or video image. In signal processing or computing it can be considered data without meaning; that is, data that is not being used to transmit a signal, but is simply produced as an unwanted by-product of other activities. In Information Theory, however, noise is still considered to be information. In a broader sense, film grain or even advertisements in web pages can be considered noise. Look up noise in Wiktionary, the free dictionary. ... Sound is a disturbance of mechanical energy that propagates through matter as a wave. ... Noise pollution (or environmental noise in technical venues) is displeasing human or machine created sound that disrupts the environment. ... This article is about the engineering discipline. ... Snow is a type of precipitation in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. ... This article does not cite any references or sources. ... For other uses, see Data (disambiguation). ... In telecommunication, signaling has the following meanings: The use of signals for controlling communications. ... Not to be confused with information technology, information science, or informatics. ... The ASCII codes for the word Wikipedia represented in binary, the numeral system most commonly used for encoding computer information. ...


Noise can block, distort, or change the meaning of a message in both human and electronic communication.


In many of these areas, the special case of thermal noise arises, which sets a fundamental lower limit to what can be measured or signaled and is related to basic physical processes at the molecular level described by well known simple formulae. Johnson-Nyquist noise (sometimes thermal noise, Johnson noise or Nyquist noise) is the noise generated by 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 electrons). ...

Contents

Acoustic noise

When speaking of noise in relation to sound, what is commonly meant is meaningless sound of greater than usual volume. Thus, a loud activity may be referred to as noisy. However, conversations of other people may be called noise for people not involved in any of them, and noise can be any unwanted sound such as the noise of aircraft, neighbours playing loud music, or road sounds spoiling the quiet of the countryside.


For film sound theorists and practitioners at the advent of talkies c.1928/1929, noise was non-speech sound or natural sound and for many of them noise (especially asynchronous use with image) was desired over the evils of dialogue synchronized to moving image. The director and critic René Clair writing in 1929 makes a clear distinction between film dialogue and film noise and very clearly suggests that noise can have meaning and be interpreted: "...it is possible that an interpretation of noises may have more of a future in it. Sound cartoons, using "real" noises, seem to point to interesting possibilities" ('The Art of Sound' (1929)). Alberto Cavalcanti uses noise as a synonym for natural sound ('Sound in Films' (1939)) and as late as 1960, Siegfried Kracauer was referring to noise as non-speech sound ('Dialogue and Sound' (1960)).


Audio noise

Main article: Colors of noise

In audio, recording, and broadcast systems audio noise refers to the residual low level sound (usually hiss and hum) that is heard in quiet periods of programme. Although noise is a random signal, it can have characteristic statistical properties. ... Broadcasting is the distribution of audio and/or video signals which transmit programs to an audience. ...


In audio engineering it can also refer to the unwanted residual electronic noise signal that gives rise to acoustic noise heard as 'hiss'. This signal noise is commonly measured using A-weighting or ITU-R 468 weighting Audio engineering is a part of audio science dealing with the recording and reproduction of sound through mechanical and electronic means. ... Electronic noise In any electronic circuit, there exist random variations in current or voltage caused by the random movement of the electrons carrying the current as they are jolted around by thermal energy. ... The A-weighting curve is one of a family of curves defined in IEC179 and various other standards for use in sound level meters. ... The ITU-R 468-weighting curve (originally defined in CCIR recommendation 468) is widely used when measuring noise in audio systems, especially in the UK, Europe, and former countries of the British Empire such as Australia and South Africa. ...


Electronic noise

Main article: Electronic noise

Electronic noise exists in all circuits and devices as a result of thermal noise, also referred to as Johnson Noise. Semiconductor devices can also contribute flicker noise and generation-recombination noise. In any electronic circuit, there exist random variations in current or voltage caused by the random movement of the electrons carrying the current as they are jolted around by thermal energy. The lower the temperature the lower is this thermal noise. This same phenomenon limits the minimum signal level that any radio receiver can usefully respond to, because there will always be a small but significant amount of thermal noise arising in its input circuits. This is why radio telescopes, which search for very low levels of signal from stars, use front-end low-noise amplifier circuits, usually mounted on the aerial dish, and cooled with liquid nitrogen. Associated with all electronic circuits is noise. ... Electronic noise In any electronic circuit, there exist random variations in current or voltage caused by the random movement of the electrons carrying the current as they are jolted around by thermal energy. ... Johnson-Nyquist noise (sometimes thermal noise, Johnson noise or Nyquist noise) is the noise generated by 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 electrons). ... 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. ... Generation-Recombination noise, or g-r noise, is a type of electrical signal noise caused statistically by the fluctuation of the generation and recombination of electrons in semiconductor-based photon detectors. ... An electronic circuit is an electrical circuit that also contains active electronic devices such as transistors or vacuum tubes. ... Random redirects here. ... Electric current is the flow (movement) of electric charge. ... International safety symbol Caution, risk of electric shock (ISO 3864), colloquially known as high voltage symbol. ... Johnson-Nyquist noise (sometimes thermal noise, Johnson noise or Nyquist noise) is the noise generated by 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 electrons). ... In a communications system, the signal level is the signal power or intensity at a specified point and with respect to a specified reference level, e. ... For the device which is a tuner (radio) and a amplifier and/or loudspeaker, see receiver (home stereo). ... Johnson-Nyquist noise (sometimes thermal noise, Johnson noise or Nyquist noise) is the noise generated by 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 electrons). ... In contrast to an ordinary telescope, which produces visible light images, a radio telescope sees radio waves emitted by radio sources, typically by means of a large parabolic (dish) antenna, or arrays of them. ... STARS can mean: Shock Trauma Air Rescue Society Special Tactics And Rescue Service, a fictional task force that appears in Capcoms Resident Evil video game franchise. ... In their most general meanings, the terms front end and back end refer to the initial and the end stages of a process flow. ... The low noise amplifier (LNA) is a special type of electronic amplifier or amplifier used in communication systems to amplify very weak signals captured by an antenna. ... A parabolic reflector (also known as a parabolic dish or a parabolic mirror) is a reflective device formed in the shape of a paraboloid of revolution. ... General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless gas Standard atomic weight 14. ...


External links

  • Noise International Sydney. Music for Film and TV
  • Aercoustics Engineering Limited. Consultants in Acoustics, Noise and Vibration
  • Audio Measuring Articles - Electronics
  • Mohr on Receiver Noise: Characterization, Insights & Surprises
  • Fundamentals of Electrical Noise
  • Noise voltage - Calculation and Measuring of Thermal Noise
  • Noise at work European Agency for Safety and Health at Work (EU-OSHA)

  Results from FactBites:
 
Noise (2314 words)
Although internal noise was the major preoccupation of aircraft acoustic engineers for many years and still is important, the noise produced by the aircraft engine and experienced on the ground has become a dominant factor in the acceptability of the airplane.
External noise is affected by the location of the source and observer, the engine thrust, and a number of factors that influence the overall configuration design.
Noise maps typically depict the DNL 65dB contour as this is identified by federal guidelines as the threshold level of aviation and community noise that is "significant".
Noise - Wikipedia, the free encyclopedia (1168 words)
Environmental noise is governed by noise regulations which set maximum recommended levels of sound levels for specific land uses, such as residential areas, schools, areas of outstanding natural beauty, or factories.
Noise is often generated deliberately and used as a test signal.
In video and television, noise refers to the random dot pattern that is superimposed on the picture as a result of electronic noise, the 'snow' that is seen with poor (analog) television reception or on VHS tapes.
  More results at FactBites »

 
 

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