Interaural time and amplitude discrimination in noise.

Just-noticeable differences (jnds) of both interaural time delay (ITD) and interaural intensity difference (IID) were measured for binaural tones in the presence of broadband maskers. The tones were presented at 50 dB SPL, the target frequency was 500 Hz, and the masker frequency was 100-1000 Hz, with various combinations of ITD and IID. The time and amplitude jnds exhibit similar dependencies on target-to-masker ratio and masker type. At a given target-to-masker ratio, discrimination was generally best in the presence of diotic maskers and worst in the presence of the interaurally out-of-phase maskers. Results for the other masker types examined tended to fall in between these two extremes. Many of these data trends are consistent with predictions of the lateralization model and the position-variable model based on auditory-nerve activity.