Acoustic Vehicle Alerting Systems (AVAS) - Regulations, Realization and Sound Design Challenges

Vehicles powered by electric machines offer the advantage to be more silent than vehicles equipped with an internal combustion engine. On the one hand, the reduced noise levels enable an improvement of the inner-city noise pollution. On the other hand, quiet vehicles entail risks not to be acoustically detected by surrounding pedestrians and cyclists in the lower speed range. The emitted noise can easily be masked by the urban background noise. Therefore, the UNECE has founded an informal working group which is currently developing guidelines in terms of an exterior noise required for detecting Quiet Road Transport Vehicles (QRTV). With the introduction of an Acoustic Vehicle Alerting System (AVAS), not only the exterior noise but also the perceived interior noise for an enhanced driving experience can be considered. Nevertheless, car manufactures have a big interest in maintaining their perceived brand identity. For the solution of this task, a synthetic sound generation system has been developed. Besides the realization of executable software for real-time capable vehicle communication and sound calculation, an implementation on an in-vehicle control unit has been engineered. Special attention has been paid to the aspect “ease of use”. Important control parameters of the sound design can be modified with a graphical user interface directly in a road test from both in- and outside the test vehicle. The methodology of the AVAS, different sound design approaches for various demonstrator vehicles and key results regarding the audibility and sound quality are object of this paper.