SPATIAL AND SPECTRAL RELEASE FROM MASKING IN 3-DIMENSIONAL AUDITORY DISPLAYS

The extent to which simultaneous sounds in three-dimensional (3D) audi tory displays mask one another was examined as a function of their spe ctral proximity and spatial separation. A tonal signal of either 0.5 o r 4 kHz was presented at 0 deg azimuth in the horizontal plane of the listener's head. Spectral proximity was varied by centering a notched- noise masker on the signal frequency and varying the notch width. The masker was presented at an azimuth of 0, 20, or 40 deg, and the listen er's head was immobilized. Detection levels decreased with both masker notch width and spatial separation. Analysis of the results shows tha t spatial separation produces both a broadening of the band over which masking is effective and a decrease in the minimum signal-to-noise ra tio needed to detect the signal at all notch widths. Both effects were greater at 0.5 kHz than at 4 kHz. Additional experiments showed that these mechanisms are disrupted when two maskers are positioned symmetr ically around the signal and head. The results are interpreted in term s of the effects of spatial separation on binaural processing and the listener's ability to resolve the signal and masker in frequency.