Effects of headtracker latency in virtual audio displays

A critical parameter for the design of interactive virtual audio displays is the maximum acceptable amount of delay between the movement of the listener's head and the corresponding change in the spatialized signal presented to the listener's ears. Two studies that used a low-latency virtual audio display to evaluate the effects of headtracker latency on auditory localization are presented. The first study examined the effects of headtracker delay on the localization on broad-band sounds. The results show that latency values in excess of 73 ms result in increased localization errors for brief sounds and increased localization response times for continuous sound sources. The second study measured how well listeners could detect the presence of headtracker latency in a virtual sound. The results show that the best listeners can detect latency values of 60-70 ms for isolated sounds, and that their detection thresholds are 25 ms lower for sounds presented in conjunction with a low-latency reference tone. These results suggest that headtracker latency values lower than 60 ms are likely to be adequate for most virtual audio applications, and that delays of less than 30 ms are difficult to detect even in very demanding virtual auditory environments.