Binaural Interaction of Impulsive Stimuli and Pure Tones

Abstract

An experiment in binaural lateralization was performed to measure the time intensity trade for pure tones and impulsive stimuli of varied frequency content. The intensity difference between the stimulus at each ear was set by the experimenter. The subject then varied the relative timing of the two stimuli and reversed the inputs to the ears until the fused image was in “null” position. This was done for all pass, high-pass, and low-pass clicks at a repetition rate of 20 pulses per second and pure tones at frequencies 200, 500, and 700 cps. Mean intensities of 20, 30, 40 db SL, and intensity differences of 0, 4, and 6 db were measured. The results indicate a difference between high and low frequencies. For instance, the first-order coefficient of the time vs intensity trade, a1, at 20 db SL varies from ∼0.100 msec per db when frequencies above 3000 cps are present, to ∼0.030 msec/db when only frequencies below 1000 cps are present. The values of a1 for pure tones are similar to those of low-pass clicks with frequency cutoffs equal to the frequency of the pure tones.