Measuring directional masking in a sound field using adaptive threshold procedures

The accuracy of three adaptive threshold procedures for measuring directional masking was assessed in two experiments. For each experiment, detection of a target signal, located at either 0$^{\circ}$, 90$^{\circ}$, 180$^{\circ}$ or 270$^{\circ}$ azimuth was measured in the presence of a masker located at 0$^{\circ}$, 90$^{\circ}$ or 180$^{\circ}$ azimuth. In Experiment 1, masked thresholds for ten normal hearing subjects were measured using the Bekesy Procedure and an Ascending Up-and-Down Procedure. In Experiment 2, masked thresholds for another group of ten normal hearing subjects were measured using the Bekesy Procedure and a Maximum Likelihood Procedure. Results confirmed the dependence of detection thresholds on the angular separation between the target and masker. In addition, threshold reliability depended on the location of the signal and the masker. No statistically significant differences were found in detection thresholds over repeated trials or between threshold procedures in Experiment 1 or 2.