Perceived sound quality of exterior sounds of an electric vehicle

New legislations stipulate that electric vehicles (EVs) must emit additional sounds. These sounds should be intuitively recognisable as a vehicle in operation and alert pedestrians, cyclists, and other road users of the vehicle's approach to prevent collisions. Additionally, these sounds influence impressions of the vehicle brand. Two experiments evaluated the sound quality of an EV emitting additional sounds from the perspective of a pedestrian in a virtual and a real-world traffic scenario. Perceived sound quality of the EV exterior sounds was evaluated in terms of a) objective measurement of detection rate (detection distance/time), and b) subjective ratings of "recognisability as vehicle", "detectability" of the sounds, and "powerfulness" and "pleasantness" of the vehicle brand. Sound pressure level, loudness, sharpness, and roughness were found to be the key metrics of the EV exterior sounds that had significant strong correlation (p<.05) with one or more of the objective and subjective perceived sound quality measures. Detection rate did not correlate to subjective ratings. Therefore, vehicle sounds that are more detectable may not be more recognizable, or portray a positive impression of the vehicle brand. Overall, a more holistic evaluation of these EV exterior sounds is recommended.