Noise Noise Active noise control (also known as noise cancellation, active noise reduction (ANR) or antinoise) is a method for preventing unwanted sound. Sound consists of vibrations in the air, which can be represented as a wave. If a speaker emits a sound whose wave has the same amplitude and the opposite phase to the original sound, the waves cancel out and the result is no sound at all. A computer analyses the waveform of the background aural or nonaural noise, then generates a similar waveform rotated 180° out of phase to cancel it out by interference. This waveform has identical or directly proportional amplitude to the waveform of the noise, but its phase is the opposite. This creates destructive interference that reduces the amplitude of the perceived noise. ...more on Wikipedia about "Active noise control"
In communications, the additive white Gaussian noise (AWGN) channel model is one in which the only impairment is the linear addition of wideband or white noise with a constant spectral density (expressed as watts per hertz of bandwidth) and a Gaussian distribution of amplitude. The model does not account for the phenomena of fading, frequency selectivity, interference, nonlinearity or dispersion. However, it produces simple, tractable mathematical models which are useful for gaining insight into the underlying behavior of a system before these other phenomena are considered. ...more on Wikipedia about "Additive white Gaussian noise"
In telecommunications, ambient noise level or room noise level is the level of acoustic noise existing at a given location, such as in a room, in a compartment, or at a place out of doors. ...more on Wikipedia about "Ambient noise level"
In telecommunication, antenna noise temperature is the temperature of a hypothetical resistor at the input of an ideal noise-free receiver that would generate the same output noise power per unit bandwidth as that at the antenna output at a specified frequency. ...more on Wikipedia about "Antenna noise temperature"
Artificial noise in the context of sports is the use of sound-making or amplifying devices. This practice is frowned upon by most sports leagues and conferences as an attempt to give the home team an unfair advantage. ...more on Wikipedia about "Artificial noise"
In statistics, autoregressive moving average (ARMA) models, sometimes called Box-Jenkins models after George Box and G. M. Jenkins, are typically applied to time series data. ...more on Wikipedia about "Autoregressive moving average model"
Aviation noise is a form of environmental noise. ...more on Wikipedia about "Aviation noise"
Black noise is noise that has a frequency spectrum of predominantly zero power level over all frequencies except for a few narrow bands or spikes. An example of black noise in a facsimile transmission system is the spectrum that might be obtained when scanning a black area in which there are a few random white spots. Thus, in the time domain, a few random pulses occur while scanning. ...more on Wikipedia about "Black noise"
Car noise is generated by the engine and friction of the tyres as they move across the road surface as well as voluntary sources of noise a car might make, such as a music centre or its horn. Car noise has decreased over time due to inventions like the muffler/ silencer attached to the exhaust pipe and better engine construction. ...more on Wikipedia about "Car noise"
Carrier-to-receiver noise density ( C /k T ): In satellite communications, the ratio of the received carrier power to the receiver noise power density. ...more on Wikipedia about "Carrier-to-receiver noise density"
In telecommunication, the term channel noise level has the following meanings: ...more on Wikipedia about "Channel noise level"
Circuit noise level: At any point in a transmission system, the ratio of the circuit noise at that point to an arbitrary level chosen as a reference. ...more on Wikipedia about "Circuit noise level"
: Grey noise is noise subjected to a psychoacoustic equal loudness curve (such as an inverted A-weighting curve) over a given range of frequencies, so that it sounds like it is equally loud at all frequencies. Some people say that this would be a better definition of "white noise" than the "equal power at all frequencies" definition, since white light, never has an equal power spectrum, but rather can have a range of spectra, for example that of a 5400 K black body. ...more on Wikipedia about "Colors of noise"
Cosmic noise is random noise that originates outside the Earth's atmosphere. ...more on Wikipedia about "Cosmic noise"
CX is a form of noise reduction for recorded audio in the analog domain. It was developed by CBS Laboratories (a division of CBS) in the early 1980s, as a competitor to other noise reduction (NR) systems as Dolby and dbx. ...more on Wikipedia about "CX (audio)"
dbx is a noise reduction system for analog tape recording and North American TV broadcasting. It works by a process called "linear decibel companding" - compressing the signal on recording and expanding it on playback. It was invented by David E. Blackmer of dbx, Inc. in 1971. ...more on Wikipedia about "Dbx (noise reduction)"
Dolby NR is a noise reduction system developed by Dolby Laboratories for use in analogue magnetic tape recording. It works by companding, i.e. reducing the dynamic range of the sound during recording and expanding it during playback. It is not the only system that works in this way, but it is the most widely used. ...more on Wikipedia about "Dolby noise reduction system"
In telecommunications, effective input noise temperature is the source noise temperature in a two- port network or amplifier that will result in the same output noise power, when connected to a noise-free network or amplifier, as that of the actual network or amplifier connected to a noise-free source. If F is the noise figure numeric and 290 K the standard noise temperature, then the effective noise temperature is given by T n = 290(F-1). ...more on Wikipedia about "Effective input noise temperature"
In telecommunication, an equivalent noise resistance is a quantitative representation in resistance units of the spectral density of a noise- voltage generator, given by ...more on Wikipedia about "Equivalent noise resistance"
Fixed pattern noise is the term given to a particular noise pattern on digital imaging sensors often noticeable during longer exposure shots where particular pixels are susceptible to giving brighter intensities above the general background noise. ...more on Wikipedia about "Fixed pattern noise"
In telecommunication, FM improvement factor is the quotient obtained by dividing the signal-to-noise ratio (SNR) at the output of an FM receiver by the carrier-to-noise ratio (CNR) at the input of the receiver. ...more on Wikipedia about "FM improvement factor"
In telecommunication, FM improvement threshold is the point in an FM ( frequency modulation) receiver at which the peaks in the RF signal equal the peaks of the thermal noise generated in the receiver. A baseband signal-to-noise ratio of about 30 dB is typical at the improvement threshold, and this ratio improves 1 dB for each decibel of increase in the signal above the threshold. ...more on Wikipedia about "FM improvement threshold"
The term Friis' equation can refer to either of two formulas used in telecommunications engineering. The first, discussed here, is used to compute the noise figure or noise temperature of a receiver composed of a number of cascaded stages. The second, called the Friis Transmission Equation, is used in computing transmission of signals between two antennas using electromagnetic waves, and is discussed in a separate article. ...more on Wikipedia about "Friis' formula"
Gaussian noise is noise that has a probability density function (pdf) of the Normal distribution (aka Gaussian distribution). ...more on Wikipedia about "Gaussian noise"
Averaging is a special case of discrete convolution. For a 3 by 3 neighbourhood, the convolution mask M is: ...more on Wikipedia about "Generalized signal averaging"
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