The effect of vehicle source intensity on auditory time-to-collision estimation

To safely cross a street while a vehicle is approaching, pedestrians must estimate how long it will take for the vehicle to reach their position. Recent studies have shown that estimation of a vehicle's arrival time (i.e., time-to-collision (TTC) estimation) is affected by the intensity of the vehicle’s sound. When presented with the same actual TTC, louder sound sources were perceived as arriving earlier than quieter sources (the so-called “intensity-arrival effect”). However, in these experiments the vehicle source intensity was varied from trial to trial, potentially directing participants’ attention to the intensity variation. Here, we used high fidelity acoustic simulations of approaching vehicles, to investigate whether the effect of source intensity on auditory TTC estimation persists when the source intensity is varied from block to block rather than from trial to trial. Results showed a significant intensity-arrival effect for the blockwise intensity variation. However, this effect was much weaker compared to a condition where the vehicle source intensity varied from trial to trial.