Masker Level And Sinusoidal-Signal Detection

Threshold signal‐to‐masker ratios (S/M's) for three sinusoids (250, 1000, or 4000 cps) presented in an identical frequency‐masker set to from about 0 to 85 dB sensation level (SL) were gathered in this preliminary study. A two‐interval, forced‐choice procedure was used. The masker was either “continuous” (a signal‐detection paradigm) or “pulsed,” i.e., gated ON only during both two‐signal intervals (a paired‐comparison paradigm). Results agree with previous reports in that the “continuous” masker resulted in considerably lower threshold S/M's than did the “pulsed” masker and the size of the thresholds were generally inversely related to the masker SL. However, plateaus were visible in the functions relating threshold S/M's to masker SL. These plateaus, between 35 and 50 and between 75 and 85 dB SL in the “continuous” masker, appear to coincide with the two negatively sloped portions of the frequency distributions of auditory neuron thresholds as a function of stimulus level reported in 1962 by Katsuki, Suga, and Kanno. Some possible implications of these observations, with regard to the auditory neural‐coding scheme for stimulus intensity, are discussed. [Work supported in part by the National Institutes of Health, U. S. Department of Health, Education, and Welfare.]