The interaction between head-tracker latency, source duration, and response time in the localization of virtual sound sources

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Brungart, D. S.
Simpson, B. D.
McKinley, R. L.
Kordik, A. J.
Dallman, R. C.
Ovenshire, D. A.
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One of the fundamental limitations on the fidelity of interactive virtual audio display systems is the delay that occurs between the time a listener changes his or her head position and the the time the display changes its audio output to reflect the corresponding change in the relative location of the sound source. In this experiment, we examined the impact that six difference headtracker latency values (12, 20, 38, 73, 145 and 243 ms) had on the localization of broadband sound sources in the horizontal plane. In the first part of the experiment, listeners were allowed to take all the time they needed to point their heads in the direction of a continuous sound source and press a response switch. In the second part of the experiment, the stimuli were gated to one of eight different durations (64, 125, 250, 375, 500, 750, 1000 and 2000 ms) and the listeners were required to make their head-pointing responses within two seconds after the onset of the stimulus. In the openended response condition, the results showed that latencies as long as 243 ms had no impact on localization accuracy, but that there was an increase in response time when then latency was longer than 73 ms. In contrast, the data from the time-limited response conditions showed that latencies that exceeded 73 ms had no impact on response time but that they significantly increased the angular localization error and the number of front back confusions. Together with the results of earlier studies, these results suggest that headtracker latency values of less than 70 ms are adequate to obtain acceptable levels of localization accuracy in virtual audio displays.
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