APA Dictionary of Psychology

a change in detection threshold for auditory stimuli produced by changes in the interaural characteristics of the masker or the signal (see auditory masking). The typical reference is the signal threshold in the diotic condition (N0S0), in which a pure-tone signal and noise masker are both presented in phase at the ears. For a dichotic condition, such as N0Sπ (noise in phase, signal 180° out of phase), the detection threshold may be 15 dB lower. The MLD and related phenomena have provided valuable insights into the mechanisms involved in binaural hearing and sound localization (see auditory localization). Also called binaural masking level difference (BMLD).