signal-to-noise ratio

Signal-to-noise ratio (often abbreviated SNR or S/N) is an electrical engineering concept defined as the ratio of a signal power to the noise power corrupting the signal. In less technical terms, signal-to-noise ratio compares the level of a desired signal (such as music) to the level of background noise. The higher the ratio, the less obtrusive the background noise is.
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The ratio of the amplitude of the desired signal to the amplitude of noise signals at a given point in time. [JP1] Note 1: SNR is expressed as 20 times the logarithm of the amplitude ratio, or 10 times the logarithm of the power ratio. Note 2: SNR is usually expressed in dB and in terms of peak values for impulse noise and root-mean-square values for random noise. In defining or specifying the SNR, both the signal and noise should be characterized, e.g., peak-signal-to-peak-noise ratio, in order to avoid ambiguity.

1. <communications> (SNR, "s/n ratio", "s:n ratio") "Signal" refers to useful information conveyed by some communications medium, and "noise" to anything else on that medium. The ratio of these is usually expressed logarithmically, in decibels.
2. The term is often applied to Usenet newsgroups though figures are never given. Here it is quite common to have more noise (inappropriate postings which contribute nothing) than signal (relevant, useful or interesting postings). The signal gets lost in the noise when it becomes too much effort to try to find interesting articles among all the crud. Posting "noise" is probably the worst breach of netiquette and is a waste of bandwidth.
[Jargon File]
(1996-01-29)

Noun
1. the ratio of signal intensity to noise intensity
(synonym) signal-to-noise, signal/noise ratio, signal/noise, S/N
(hypernym) ratio