Speaker
Description
For a pedestrian standing at the curb and intending to cross the road, the dynamic spatial sound field generated by an approaching vehicle provides various cues to its arrival time (time-to-collision, TTC). The sound intensity at the listener position increases with decreasing vehicle distance. The azimuthal position of the vehicle and the angular separation of the vehicle sound sources (e.g., left and right front tires) change with distance. Here, we investigated which cues are most relevant for auditory TTC judgments. Using acoustic simulations of approaching vehicles, the TTC and speed signaled by the dynamic intensity cues were shifted against the TTC and speed signaled by the change in the simulated spatial position of the simulated sound sources (i.e., the angular cues). This is only possible in virtual environments. In the real world, these cues are inseparable. The vehicle sound power and the vehicle size were also varied. The results showed a significant association of both intensity cues and angular cues with the estimated TTC. However, general dominance weights indicated a higher importance of intensity cues compared to angular cues. Also, the sound level at the time of TTC estimation, a “heuristic” cue, showed a higher cue importance than the TTC signaled by the dynamic intensity cues. At a given presented TTC, participants estimated shorter TTCs for vehicles with higher sound power, compatible with previous results. Taken together, the data provide novel insights into which acoustic cues pedestrians use for auditorily estimating the TTC of an approaching vehicle. The observed cue weights are discussed in relation to the reliability of the different acoustic cues to TTC.