Editing Signal-to-noise ratio (section)

{{short description|Ratio of the desired signal to the background noise}}
{{redirect|Signal-to-noise|statistics|Effect size|other uses|}}
{{distinguish|Signal-to-interference-plus-noise ratio}}

[[File:SNR image demonstration.png|thumb|A gray-scale photography with different signal-to-noise ratios (SNRs). The SNR values are given for the rectangular region on the forehead. The plots at the bottom show the signal intensity in the indicated row of the image (red: original signal, blue: with noise).]]
'''Signal-to-noise ratio''' ('''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 processing)|noise]]. SNR is defined as the ratio of signal [[Power (physics)|power]] to [[noise power]], often expressed in [[decibel]]s. A ratio higher than 1:1 (greater than 0&nbsp;dB) indicates more signal than noise.

SNR is an important parameter that affects the performance and quality of systems that process or transmit signals, such as [[communication system]]s, [[audio system]]s, [[radar system]]s, [[imaging system]]s, and [[data acquisition]] systems. A high SNR means that the signal is clear and easy to detect or interpret, while a low SNR means that the signal is corrupted or obscured by noise and may be difficult to distinguish or recover. SNR can be improved by various methods, such as increasing the signal strength, reducing the noise level, filtering out unwanted noise, or using error correction techniques.

SNR also determines the maximum possible amount of data that can be transmitted reliably over a given channel, which depends on its bandwidth and SNR. This relationship is described by the [[Shannon–Hartley theorem]], which is a fundamental law of information theory.

SNR can be calculated using different formulas depending on how the signal and noise are measured and defined. The most common way to express SNR is in decibels, which is a logarithmic scale that makes it easier to compare large or small values. Other definitions of SNR may use different factors or bases for the logarithm, depending on the context and application.