Effects of tone intensity and frequency on discrimination of the sound stimulus transition process

In our research, we determined the dependence of human detection of differences in the sound stimulus transition process upon sound intensity and frequency. We established that the discrimination threshold for the stimulus rise time (delta tau r) is approximately 1.5 msec at low and intermediate tone frequencies and increases to 5-6 msec during an increase in frequency from 10 to 15 kHz. It was shown that the ability of a human to discriminate a stepwise change in the stimulus envelope depends upon the duration of the steps. For steps of short duration (up to 7 msec), a linear decrease in the discrimination threshold value for detecting a drop in step amplitude (delta I) occurs with increasing duration of the step (t). For a step duration greater than 7 msec, the discrimination threshold for a drop in amplitude remains constant, equaling a value on the order of 3.5 dB. It was found that the values of delta tau r and delta I rapidly decrease with an increasing level of stimulus intensity in the range of 10-40 dB and remain practically constant in the range of 40-80 dB.