a) The ratio of signal to noise expressed in dB. In general, the higher the signal to noise ratio the better. If there is a low signal-to-noise ratio, the picture can appear grainy, snowy, and sparkles of color may be noticeable. Equipment will not be able to synchronize to extremely noisy signals. b) It may not be possible to directly compare SNRs for ATV and for NTSC as the eye’s sensitivity to noise varies with the detail of the noise. c) The measurement of the dynamic range of a piece of equipment, measuring from the noise floor (internally generated noise) to the normal operating level or the level prior to limiting.