Sensitivity to Changes in the Interruption Rate of White Noise

Abstract

Difference-limens for the discrimination of intermittence were obtained at 10 interruption rates of random noise between 1 and 320 cps. The duty cycle of the intermittent noise was 0.5 and the sound pressure level was 75 db. Data from 4 listeners give average deviations from the standard frequency ([DELTA]F) of 0.02 to 9.74 cps. The graph relating [DELTA]F and F from 1 to 320 cps shows [DELTA]F to be a monotonically increasing function of F. When the data are plotted with logarithmic coordinates, two functions are revealed, suggesting a change in the method of frequency discrimination at about 5 cps. This change appears due to the listener''s ability to count the noise bursts from 1 to 5 cps, but not above about 5 cps. The relationship between 5 and 320 cps may be described by a function of the form y=axb. Below 5 cps, the form of the relationship cannot be determined from the data available. The relative difference-limen, [DELTA]F/F, lies between 0.008 and 0.03, and graphic integration of 1/[DELTA]F yields 560 just-noticeable-differences in the range studied. These data show difference-limens for flutter that are smaller than those previously reported.