The signal-to-noise ratio (SNR) is the ratio between the variance of the signal and the variance of the noise in a given image.6 This measure is extremely useful in assessing the quality of experimental data, as well as the power of 2D and 3D averaging methods. Unfortunately, the definition varies among different fields, with the SNR often being the square root of the above definition, or with the numerator being measured peak to peak. In the following we will use the ratio of variances, which is the most widely used definition in digital signal processing.

6Note that in the field of electrical engineering, the signal-to-noise ratio is defined as the ratio of the signal power to the noise power. This ratio is identical with the variance ratio only if the means of both signal and noise are zero.

The sample variance of an image indexed i, {py; j = 1,..., J is defined as with the sample mean y,

Was this article helpful?

## Post a comment