Signal and noise

Electronics and telecommunications engineers distinguish between the signal that is being communicated between two locations and the random noise that is added by the communications channel. The noise degrades the signal and, in the worst cases, can make the signal difficult to detect.

The word "CAST" is hard to read in the following noisy image.

Audio equipment often quotes its signal-to-noise ratio as a measure of quality. Noise again deteriorates the signal — the 'perfect' music that you want to hear.

Signal   =   information you want
Noise   =   'random' modification to the signal

The concepts of signal and noise also apply to data sets.