Time-Intensity Trading Functions for Selected Pure Tones

A substantial number of investigations have examined the ability of the auditory system to trade time for intensity on a lateralization task. Most of these investigations, however, have employed clicks and noise bursts as stimuli with interaural disparities between onset times. Consequently, there is a lack of quantitative data for time-intensity trades where pure tones that had identical onset times but disparate phase were employed as signals. For this reason we employed sinusoids ranging from 200 to 2000 Hz and determined the extent to which the intensity of one signal must be decreased to achieve a midline image when interaural phase disparities of 0 degrees to 360 degrees were imposed between the binaural signals in 30 degree increments. The time-intensity trading functions yielded in this experiment demonstrate that (1) not unexpectedly, the largest time-intensity trades were accomplished for the lower frequencies; (2) the maximum time-intensity trade for each frequency occurred at interaural phase disparities of 90 degrees and 270 degrees; and (3) when the low-frequency tones were 180 degrees out of phase, essentially the same intraaural intensity relationship was required to achieve midline as was needed for the 0 degree interaural phase condition.