Hearing acceleration: enhancing vehicle sound for earlier detection of acceleration in pedestrians

Acceleration serves as both an implicit cue of a vehicle’s non-yielding intention and a necessary maneuver following a yielding action in autonomous vehicles (AVs). However, vehicle acceleration is difficult for pedestrians to accurately perceive. This study proposed and evaluated an auditory external interface for AVs that enhances the vehicle’s engine sound to facilitate pedestrians’ perception of acceleration. In a virtual reality environment, we measured pedestrians’ time delay in detecting vehicle acceleration under four sound conditions: untreated, amplitude-enhanced, frequency-enhanced, and combined amplitude-frequency enhancement. Results indicated that all three enhancement methods could speed up acceleration perception compared to the untreated condition, with amplitude enhancement producing the weakest effect. The combined enhancement proved most effective, offering a slight advantage over frequency enhancement. These findings provide insights into effectively enhancing auditory characteristics that may inform future research on vehicle–pedestrian interaction.