The effect of noise on the modulation transfer function was studied by means of threshold measurements. White noise and 1/f noise of various levels and different cutoff frequencies were displayed on a television screen together with a sinusoidally modulated bar pattern. The signal-to-noise threshold necessary for perception was measured as a function of the spatial frequency of the bar pattern. This signal-to-noise threshold, in addition to being strongly dependent on the bar-pattern frequency is also dependent on the rms value and the frequency distribution of the noise as well as the difference between the bar-pattern frequency and medium frequency of the noise. An attempt was made to explain the results by visual observation of the bar pattern in the presence of narrow-bandwidth noise.
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