Exterior Sound for User-Car Interaction

Abstract

The advent of electric and hybrid vehicles have, compared to traditional combustion engine vehicles drastically decreased the total noise emitted. One downside of lower noise levels is that it is becoming increasingly difficult for people, especially those whoarevisuallyimpaired,todetectthesevehiclesastheyhardlyproduceanynoise. Especially when these vehicles are driven at speeds below 30 km/h, where there is not much tyre and wind noise produced by the vehicle, detecting them becomes difficult. To increase the detectability of these vehicles, various organisations across the world e.g. National Highway Traffic Safety Administration (NHTSA) in USA have come up with regulations which requires that all vehicles which are able to be be electrically driven to emit artificial sound above a certain minimum level across different third octave bands. This thesis investigates and presents the complete process of enabling a vehicle to emit sounds. An evaluation of different sound sources is done for which artificial sounds in different categories are designed. With the chosen sound setup and the developed sounds a listening test is done to evaluate the sounds with the goal of finding the most suitable sound. Furthermore, a possible correlation of the sounds with psychoacoustic parameters should make it easier to identify suitable sounds. The thesis has three major parts which are the evaluation of the right sound source, a design process for artificial sounds and a listening test. Out of a loudspeaker setup and different shaker setups mounted on different body parts on the vehicle, the loudspeaker setup yields the best results. In the creative process of designing sounds, eight sounds with different frequency components were designed. The listening test shows that broadband sounds are perceived as very pleasant but tonal components are needed for safety reasons. A recommendation of a sound is done. The correlation of the results show similarities with the tone to noise ratio but need further investigation.