Subjective quality of television pictures impaired by random noise
R.D. Prosser, J.W. Allnatt · Proceedings of the Institution of Electrical Engineers · 1965
Using a previously proposed quality-grading method, tests have been made of the effect of both flat and triangular random noise on still, monochrome, 625-line pictures typical of scenes in television broadcasting. 50% favourable opinions are obtained with a signal/weighted-noise ratio of 36db and 95% favourable opinions with a ratio of 39db.