Detection of intensity differences between brief contiguous tonal bursts

Abstract

Two experiments have been performed to examine the relative roles of a short-term memory and temporal integration or summation mechanism in the detection of intensity differences between brief contiguous tone bursts. Tonal frequency was 1000 Hz. Two tone-burst durations (320 msec and 80 msec) and two interburst interval (IBI) durations (320 msec and 25 msec) were employed. A 2AFC presentation paradigm was employed and psychometric functions plotting percent correct vs. intensity difference between tone bursts in the variable observation interval were obtained for combinations of the signal durations and IBIs given above. In Experiment I, four bursts were employed where three had identical intensities and the fourth had an intensity decrement. This configuration resulted in unequal energy between the two observation intervals. Experiment II also used four bursts where the two bursts in the standard interval were of equal intensity; one burst in the variable interval had greater intensity and one less intensity than the bursts in the standard interval. The voltages for this experiment were set such that there would be equal energy in both observation intervals according to the equation (V12 + V12)1/2 = (V22 + V32)1/2. The results of our experiments appear to suggest that more than one mechanism underlies the detection of intensity differences between brief signals: short-term memory and temporal summation.