The Effect of Distance on Audiovisual Temporal Integration in an Indoor Virtual Environment

For several decades, it has been debated whether a distance compensation mechanism exists during audiovisual (AV) synchrony judgements, regardless of the vast difference between the speed of sound and light. Here we aimed to investigate the effect of stimulus distance on the human tolerance for (physical) asynchronies and broaden earlier findings with a state-of-the-art head-mounted display (HMD). In this study, we measured the point of subjective simultaneity (PSS) of visual and auditory stimuli in an indoor virtual environment (VE). The synchrony judgement method was used for 11 stimulus onset asynchronies (SOA) and six egocentric distances up to 30 m. In addition, to obtain higher validity of the dataset, we implemented in our data analysis the results from the previous studies of the egocentric distance perception and the AV hardware latency delay. Our findings displayed positive PSS values that increased with distance showing that in our VE, a distance compensation mechanism is taking its place. However, the gain was smaller than was expected for complete compensation for the slower speed of sound.