Measuring the binaural temporal window

Abstract

Sensitivity to small ITDs in detection and discrimination tasks was measured. In experiment 1, four listeners performed 3 tasks. The first 2 were 4I- and 2I-2AFC adaptive detection tasks. The third was a 2I-2AFC adaptive discrimination task. All stimuli were 100 ms noise bursts. Reference stimuli were diotic, and target stimuli contained a probe duration of 64, 32, 16, 8, 4, or 2 ms, which carried an interaural time delay. These probes were temporally fringed with diotic noise. Thresholds for the discrimination task were significantly higher than for the detection tasks. In experiment 2, psychometric functions were obtained from 4 participants for the six probe durations using the same 2I-2AFC detection and discrimination tasks. Binaural temporal windows were fitted to the data using a variety of fitting functions. Fits to the detection task data demonstrated narrow tips but unmeasurably long skirts. In the discrimination task neither parameter could be accurately measured, suggesting that the overall stimulus duration was too short to encompass the window. A stimulus length of 500 ms and probe durations of 256, 128, 64, 32 and 16 ms allowed both parameters to be measured. The resulting equivalent rectangular duration was approximately 50 ms.