Acoustic alerting system for electric vehicles combining directional sound technique with object tracking—towards quieter urban environments

Electric vehicles (EVs) are mandated to emit warning sounds to notify pedestrians. However, it is desirable that these warning sounds are directed precisely to vulnerable road-users, thereby avoiding unnecessary noise pollution. This paper integrates directional sound technology with object-tracking in artificial Acoustic Vehicle Alerting Systems (AVAS) for electric vehicles. Directional sound is achieved using a loudspeaker array. Real-time locations of road users are accomplished via the vehicle-mounted surround-view cameras. They are integrated to generate a sound field that can adjust its direction in real-time according to the positions of moving road-users. This system supports seven operating cases, including multiple road users in the left, middle, right, left-middle, left–right and right-middle zones of the vehicle, plus the scenario of full vehicle surrounding by road users. Offline simulations and laboratory experiments validated the AVAS effectiveness, showing that the adaptive AVAS can produce targeted directional sound fields within a small angular region, dynamically track moving objects to adjust sound orientation in real time, and cut non-target noise by over 15 dB. In areas distant from moving objects, the warning sound remains at relatively low levels. By reducing unnecessary warning sound in non-critical areas, the proposed adaptive AVAS enhances the environmental performance of EVs and contributes to quieter urban environments.