signal-to-noise ratio

5.55  signal-to-noise ratio. Ratio of a measure of a signal to the same measure of the noise. The measure may be electric power, time-mean-square voltage, time-mean-square current, or the acoustical analogs, acoustic power, time-mean-square sound pressure, time-mean-square sound particle velocity, respectively. The frequency range and statistical properties of the signal and the noise should be stated explicitly. Abbreviation, SNR or S/N.

Annotation            In controlled situations it may be possible to determine the measures of the signal power and the noise power separately and independently. In most natural conditions, however, measurements are limited to determining signal-plus-noise and noise-alone. Signal-to-noise ratio then becomes a derived quantity.