Lateralization of High-Frequency Tones

Abstract

Thresholds for interaural difference between the intensities of dichotic tone pulses were measured on five subjects by the method of constant stimuli, at frequencies between 250 and 10 000 cps and at a sensation level of 50 db. The just noticeable dichotic difference in intensity is about 1 db at 1000 cps, a little smaller at lower frequencies, and still smaller (0.5 db) at higher frequencies. This function is compared with the interaural difference in intensity produced by the just noticeable deviation from the median plane of an actual source of tone pulses. At low frequencies, where phase or time differences are generally considered more important than intensity differences for auditory localization, these two functions differ greatly. At frequencies between 1500 and 6000 cps, the threshold for a dichotic difference in intensity matches the interaural difference in intensity that is produced by the just noticeable deviation from the median plane of an actual source. The relation between the discrimination of dichotic differences in phase and intensity and the discrimination of actual direction is shown in a graphical summary.