Effect of increasing system latency on localization of virtual sounds with short and long duration
Wenzel, Elizabeth M
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In a virtual acoustic environment, the total system latency (TSL) refers to the time elapsed from the transduction of an event or action, such as movement of the head, until the consequences of that action cause the equivalent change in the virtual sound source. This paper reports on the impact of increasing TSL on localization accuracy when head motion is enabled. A previous study  investigated long duration stimuli of 8 s to provide subjects with substantial opportunity for exploratory head movements. Those data indicated that localization was generally accurate, even with a latency as great as 500 ms. In contrast, Sandvad  has observed deleterious effects on localization with latencies as small as 96 ms when using stimuli of shorter duration ( 1.5 to 2.5 s). In an effort to investigate stimuli more comparable to Sandvad , the present study repeated the experimental conditions of  but with a stimulus duration of 3 s. Five subjects estimated the location of 12 virtual sound sources (individualized head-related transfer functions) with latencies of 33.8, 100.4, 250.4 or 500.3 ms in an absolute judgement paradigm. Subjects also rated the perceived latency on each trial. Comparison of the data for the 3 and 8 ms duration stimuli indicates that localization accuracy as a function of latency is moderately affected by the overall duration of the sound. For example, for the 8-s stimuli, frontback confusions were minimal and increased only slightly with increasing latency. For the 3-s stimuli, the increase in front-back confusions with latency was more pronounced, particularly for the longest latency tested (500 ms). Mean latency ratings indicated that latency had to be at least 250 ms to be readily perceived. The fact that accuracy was generally comparable for the shortest and longest latencies suggests that listeners are able to ignore latency during active localization, even though delays of this magnitude produce an obvious spatial ``slewing'' of the source such that it is no longer stabilized in space. There is some suggestion that listeners are less able to compensate for latency with the short duration stimuli, although the effect is not as pronounced as in .