Just Noticeable Dichotic Phase Difference

Abstract

The just noticeable dichotic phase difference, as a function of sensation level and of sound frequency, has been determined on a number of listeners with normal hearing. The test tones were transmitted by earphones and the phase difference between the ears was varied by means of an electronic phase shifter. The psychophysical method used combined paired comparisons with forced choice. The first tone pulse of each pair presented was kept at a constant phase difference at which the subject localized the sound source as equidistant from his ears. The dichotic phase difference of the second pulse was varied irregularly (“randomly”). The results show that the sensitivity to dichotic phase difference is highest (2° of phase) at medium sensation levels and that the jnd increases with positive acceleration as the sound frequency increases. Around 1300 cps the jnd becomes so great that it cannot be measured. The dichotic time difference calculated from the measured jnd of phase has a minimum around 800 cps.