The effects of randomizing values of interaural disparities on binaural detection and on discrimination of interaural correlation.

The purpose of this study was to assess whether randomizing (roving) baseline interaural parameters of binaural stimuli would adversely affect performance in masking-level differences and in interaural correlation-discrimination paradigms. Listeners' detection thresholds were measured in NoSo and NoS pi configurations for both broadband (100-3000 Hz) and narrow-band (450-550 Hz) maskers centered at 500 Hz. In addition, thresholds of interaural decorrelation (from a reference correlation of 1.0) were measured for 100-Hz-wide bands of noise centered at 500 Hz. Data were obtained under conditions in which either values of ITD or values of IID were roved both within and across trials. Data were also collected in the absence of a rove. The range of the rove was +/- 500 microseconds for ITDs and was +/- 6 dB for IIDs. The duration of the stimuli was varied between 17 and 310 ms. Overall, the results indicate that, independent of duration, roving the interaural cues produced small degradations of performance as compared to data obtained in the absence of a rove. The data are inconsistent with the notion that binaural detection depends upon reliable changes in laterality produced by adding S pi signals to diotic maskers. On the other hand, the data are consistent with modern models of binaural processing.