# Signal-to-noise ratio

**signal to noise ratioSNRsignal-to-noisesignal levelnoisesignal to noiseS/NS/N ratioSignal to noise ratio (image processing)signal-to-noise-ratio**

Signal-to-noise ratio (abbreviated SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise.wikipedia

593 Related Articles

### Noise (signal processing)

**noisenoisybackground noise**

Signal-to-noise ratio (abbreviated SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise.

### Decibel

**dBdecibelsbel**

SNR is defined as the ratio of signal power to the noise power, often expressed in decibels. Because many signals have a very wide dynamic range, signals are often expressed using the logarithmic decibel scale. In audio engineering, the reference signal is usually a sine wave at a standardized nominal or alignment level, such as 1 kHz at +4 dBu (1.228 V RMS ).

In electronics, the gains of amplifiers, attenuation of signals, and signal-to-noise ratios are often expressed in decibels.

### Channel capacity

**capacitydata capacityinformation capacity**

The signal-to-noise ratio, the bandwidth, and the channel capacity of a communication channel are connected by the Shannon–Hartley theorem.

An application of the channel capacity concept to an additive white Gaussian noise (AWGN) channel with B Hz bandwidth and signal-to-noise ratio S/N is the Shannon–Hartley theorem:

### Dynamic range

**DRdynamicdynamic and tonal range**

Because many signals have a very wide dynamic range, signals are often expressed using the logarithmic decibel scale.

Dynamic range is therefore the signal-to-noise ratio (SNR) for the case where the signal is the loudest possible for the system.

### Nominal level

**nominalnominal signal level**

In audio engineering, the reference signal is usually a sine wave at a standardized nominal or alignment level, such as 1 kHz at +4 dBu (1.228 V RMS ).

In audio, a related measurement, signal-to-noise ratio, is usually defined as the difference between the nominal level and the noise floor, leaving the headroom as the difference between nominal and maximum output.

### Shannon–Hartley theorem

**Shannon-Hartley theoremHartley's lawShannon limit**

The signal-to-noise ratio, the bandwidth, and the channel capacity of a communication channel are connected by the Shannon–Hartley theorem.

### Noise (electronics)

**noiseelectronic noiseelectrical noise**

Signal-to-noise ratio is defined as the ratio of the power of a signal (meaningful information) to the power of background noise (unwanted signal):

Noise is, however, typically distinguished from interference, for example in the signal-to-noise ratio (SNR), signal-to-interference ratio (SIR) and signal-to-noise plus interference ratio (SNIR) measures.

### Low-noise amplifier

**low noise amplifierLNAlow noise receivers**

Additionally, internal noise of electronic systems can be reduced by low-noise amplifiers.

A low-noise amplifier (LNA) is an electronic amplifier that amplifies a very low-power signal without significantly degrading its signal-to-noise ratio.

### Logarithm

**logarithmsloglogarithmic function**

Because many signals have a very wide dynamic range, signals are often expressed using the logarithmic decibel scale.

The signal-to-noise ratio describing the amount of unwanted noise in relation to a (meaningful) signal is also measured in decibels.

### Communication channel

**channelchannelscommunications channel**

The signal-to-noise ratio, the bandwidth, and the channel capacity of a communication channel are connected by the Shannon–Hartley theorem.

### Eb/N0

**E b /N 0 Eb/NoE b /N 0 ratio**

Although noise levels in a digital system can be expressed using SNR, it is more common to use E b /N o, the energy per bit per noise power spectral density.

In digital communication or data transmission, E b /N 0 (energy per bit to noise power spectral density ratio) is a normalized signal-to-noise ratio (SNR) measure, also known as the "SNR per bit".

### Analog-to-digital converter

**ADCanalog to digital converteranalog-to-digital conversion**

Real analog-to-digital converters also have other sources of noise that further decrease the SNR compared to the theoretical maximum from the idealized quantization noise, including the intentional addition of dither.

The performance of an ADC is primarily characterized by its bandwidth and signal-to-noise ratio (SNR).

### Lock-in amplifier

**phase-sensitive detectorlock-indemodulated**

For example, it is sometimes possible to use a lock-in amplifier to modulate and confine the signal within a very narrow bandwidth and then filter the detected signal to the narrow band where it resides, thereby eliminating most of the broadband noise.

The device is often used to measure phase shift, even when the signals are large, have a high signal-to-noise ratio and do not need further improvement.

### Signal

**signalselectrical signalsignaling**

Signal-to-noise ratio (abbreviated SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. Signal-to-noise ratio is defined as the ratio of the power of a signal (meaningful information) to the power of background noise (unwanted signal):

### Matched filter

**matched filteringmatched-filteringNorth filters**

The matched filter is the optimal linear filter for maximizing the signal-to-noise ratio (SNR) in the presence of additive stochastic noise.

### Signal-to-interference-plus-noise ratio

**Signal-to-noise plus interferencesignal-to-interference and noise ratio (SINR)signal-to-interference-and-noise**

SINR is the Signal-to-noise-plus-interference ratio.

Analogous to the signal-to-noise ratio (SNR) used often in wired communications systems, the SINR is defined as the power of a certain signal of interest divided by the sum of the interference power (from all the other interfering signals) and the power of some background noise.

### Coefficient of variation

**CVRelative standard deviationcoefficients of variation**

An alternative definition of SNR is as the reciprocal of the coefficient of variation, i.e., the ratio of mean to standard deviation of a signal or measurement:

In signal processing, particularly image processing, the reciprocal ratio \mu/\sigma is referred to as the signal to noise ratio in general and signal-to-noise ratio (imaging) in particular.

### Film speed

**ISOISO sensitivityASA**

Yet another alternative, very specific, and distinct definition of SNR is employed to characterize sensitivity of imaging systems; see Signal-to-noise ratio (imaging).

The noise-based speed is defined as the exposure that will lead to a given signal-to-noise ratio on individual pixels.

### SINAD

**signal-to-noise and distortionsignal-to-noise and distortion ratioSignal-to-noise-and-distortion**

Note that with this definition, unlike SNR, a SINAD reading can never be less than 1 (i.e. it is always positive when quoted in dB).

### Audio system measurements

**Audio quality measurementAudio noise measurementaudio performance**

### Phase-shift keying

**QPSKBPSKPSK**

For instance an OSNR of 20 dB/0.1 nm could be given, even the signal of 40 GBit DPSK would not fit in this bandwidth.

If the signal-to-noise ratio is high (as is necessary for practical QPSK systems) the probability of symbol error may be approximated:

### Modulation error ratio

The modulation error ratio (MER) is a measure of the SNR in a digitally modulated signal.

MER is also closely related to signal-to-noise ratio.

### Video quality

**qualityfull reference metricmodels**

Among the oldest FR metrics are signal-to-noise ratio (SNR) and peak signal-to-noise ratio (PSNR), which are calculated between every frame of the original and the degraded video signal.

### Near–far problem

**near-far problemnear-far**

Since one transmission's signal is the other's noise, the signal-to-noise ratio (SNR) for the further transmitter is much lower.

### Generation loss

**digital generation lossa copy of a copy may not be as 'sharp' as the originalcopies of analog recordings tend to degrade when copied**

Digital resampling such as image scaling, and other DSP techniques can also introduce artifacts or degrade signal-to-noise ratio (S/N ratio) each time they are used, even if the underlying storage is lossless.