The metric for noise performance of a circuit is noise figure or noise factor.

If a preamplifier has been used prior to A / D conversion, the noise introduced by the amplifier can be an important contributing factor towards the overall SNR.

In addition to their small size, the surface normal operation of VCSOAs leads to a number of advantages, including low power consumption, low noise figure, polarization insensitive gain, and the ability to fabricate high fill factor two-dimensional arrays on a single semiconductor chip.

Sound intensity follows an inverse square law with distance from the source ; doubling the distance from a noise source reduces its intensity by a factor of four, or 6 dB.

The noise factor is defined as the ratio of the output noise power of a device to the portion thereof attributable to thermal noise in the input termination at standard noise temperature ( usually 290 K ).

The noise factor is thus the ratio of actual output noise to that which would remain if the device itself did not introduce noise.

The noise figure is obtained by expressing the noise factor in decibels ( dB ).

The noise factor F of a system is defined as:

The noise figure is the noise factor, given in dB:

The noise factor of a device is related to its noise temperature :< ref > with some rearrangement from T < sub > e </ sub >= T < sub > 0 </ sub >( F-1 ).</ ref >

Attenuators have a noise factor F equal to their attenuation ratio L when their physical temperature equals.

More generally, for an attenuator at a physical temperature, the noise temperature is, giving a noise factor of:

If several devices are cascaded, the total noise factor can be found with Friis ' Formula:

where is the noise factor for the n-th device and is the power gain ( linear, not in dB ) of the n-th device.

LPC may also be thought of as a basic perceptual coding technique ; reconstruction of an audio signal using a linear predictor shapes the coder's quantization noise into the spectrum of the target signal, partially masking it.

The sound of linear timecode is a jarring and distinctive noise and has been used as a sound-effects shorthand to imply ' telemetry ' or ' computers '.

Pink noise ( left ) and white noise ( right ) on an FFT spectrogram with linear frequency vertical axis ( on a typical audio or similar spectrum analyzer the pink noise would be flat, not downward-sloping, and the white noise rising )

: S / N is the signal-to-noise ratio ( SNR ) or the carrier-to-noise ratio ( CNR ) of the communication signal to the Gaussian noise interference expressed as a linear power ratio ( not as logarithmic decibels ).

** Additive white Gaussian noise ( AWGN ) channel, a linear continuous memoryless model

After years of work Black invented the negative feedback amplifier which uses negative feedback to reduce the gain of a high-gain, non-linear amplifier and makes it act as a low-gain, linear amplifier with much lower noise and distortion.

The Kalman filter, also known as linear quadratic estimation ( LQE ), is an algorithm which uses a series of measurements observed over time, containing noise ( random variations ) and other inaccuracies, and produces estimates of unknown variables that tend to be more precise than those that would be based on a single measurement alone.

There are several types of on-line corrosion monitoring technologies such as linear polarization resistance, electrochemical noise and electrical resistance.

Additive white Gaussian noise ( AWGN ) is a channel model in which the only impairment to communication is a 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 residual is then matched to a linear filter that is excited with white noise.

Since analog video is recorded by frequency-modulation of the video signal, the FM capture effect shields the signal against this noise ; however, the linear audio and ( depending on format ) chrominance signals of a video cassette may have some print effects.

As the noise is randomly distributed, it is assumed that, provided sufficient items are tested, the rank-ordering of persons along the latent trait by raw score will not change, but will simply undergo a linear rescaling.

Because of this blurring, linear filters are seldom used in practice for noise reduction ; they are, however, often used as the basis for nonlinear noise reduction filters.

With a spatially constant diffusion coefficient, this is equivalent to the heat equation or linear Gaussian filtering, but with a diffusion coefficient designed to detect edges, the noise can be removed without blurring the edges of the image.

From left to right: uncorrelated stochastic data ( white noise ), harmonic oscillation with two frequencies, chaotic data with linear trend ( logistic map ) and data from an autoregressive process | auto-regressive process.

That is followed by a linear regulator that generates exactly the desired voltage and eliminates nearly all the noise generated by the switching regulator.

Like AM, ASK is also linear and sensitive to atmospheric noise, distortions, propagation conditions on different routes in PSTN, etc.

It has been given the term " bruit ", French for noise.

The word poltergeist comes from the German words poltern (" to make noise ") and Geist (" ghost "), and the term itself literally means " noisy ghost ".

In companies that use large numbers of cubicles in a common space, employees sometimes use the term prairie dogging to refer to the action of several people simultaneously looking over the walls of their cubicles in response to a noise or other distraction.

FM radios suppress short term changes in amplitude and are therefore much less prone to noise during storms and during reception of electrical noise impulses.

In telecommunications, the term channel noise level has the following meanings:

The term psophometric weighting, though referring in principle to any weighting curve intended for noise measurement, is often used to refer to a particular weighting curve, used in telephony for narrow-bandwidth voiceband speech circuits.

In telecommunication, the term noise power has the following meanings:

The term also applies to photon counting in optical devices, where shot noise is associated with the particle nature of light.

The term can also be used to describe any noise source, even if solely mathematical, of similar origin.

Within the scientific literature the term 1 / ƒ noise is sometimes used a little more loosely to refer to any noise with a power spectral density of the form

The term flicker noise is sometimes used to refer to 1 / ƒ noise, although this is more properly applied only to its occurrence in electronic devices due to a direct current.

Mandelbrot and Van Ness proposed the name fractional noise ( sometimes since called fractal noise ) to emphasize that the exponent of the spectrum could take non-integer values and be closely related to fractional Brownian motion, but the term is very rarely used.

He designed the structure as an ' egg in a box ', a term he used to describe the separation of the curved auditorium space from the surrounding building and the noise and vibration of the adjacent railway viaduct.

PI controllers are fairly common, since derivative action is sensitive to measurement noise, whereas the absence of an integral term may prevent the system from reaching its target value due to the control action.

There are many fractal procedures ( such as Perlin noise ) capable of creating terrain data, however, the term " fractal landscape " has become more generic.

A " crack " had the sense of any loud noise, preserved in the phrase " crack of thunder ", and Doom was a term for the Last Judgement, as Doomsday still is.

The term ticker refers to the noise made by the ticker tape machines once widely used by stock exchanges.

The term is a clipping of the term " Schottky noise ," referring to the scientist who first published regarding this phenomenon.