On the effect of second task for detection of alerting sound of electric vehicles

Relative quietness of electric or hybrid electric vehicles is a matter of safety concern, because they are potentially dangerous to pedestrians when the approach of them becomes inaudible under urban noise. Hence, regulations regarding additional alerting sounds for the quiet vehicles (Acoustic Vehicle Alerting System; AVAS) have been developed in Japan as well as in global. Several studies have been conducted in different institutions to examine the feasible sound design for the AVAS to be detected in urban noise environment. In this paper, a cross-cutting perspective on the detectability of the AVAS sound compared to the background noise levels is provided. The acoustic power level of the vehicle sound, that means total acoustic power including mechanical and the alerting sound, was calculated from the sound level based on semi-free field assumption. Then the A-weighted sound pressure level al the point of the participants were estimated from the distance data in the literatures. The result suggests the effect of second task of the pedestrians. The paper also provides a pilot study on such effect through a laboratory experiment.