Localization of the direction of bursts of thermal noise was measured for both high-frequency and low-frequency bands, as a function of duration of bursts. Durations of 0.3, 1, 2, and 5 sec were used. Subjects were free to move their heads to aid in localization. Subjects were not specially trained in sound localization.
With increase in stimulus duration, perception of elevation was slightly improved for low-frequency noise, probably due to increased information from head movement. A minimum duration of the order of 2 sec appears necessary to allow subjects to achieve maximum performance (which still is not very good for these low-frequency stimuli). Perception of the elevation of the high-frequency noise sources we used was relatively good even at the briefest duration; however, variability of judgment was larger at the shorter durations.
Perception of front-back source position was much improved for both low-frequency and high-frequency noise when stimulus duration was increased. The results are understandable in terms of the increased possibility for head movement with increase in stimulus duration. It appears that one should use a minimum stimulus duration of about 2 sec if one wishes subjects to approach their most efficient performance.
High-Frequency Noise Sources in Quantum Wells
