Human Systems Integration Division @ NASA Ames

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. 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. The data indicated that localization was generally accurate, even with a latency as great as 500 ms. In particular, front-back confusions were minimal and unaffected by latency. 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.