NVH Analysis Techniques for Design and Optimization of Hybrid and Electric Vehicles Chapter 4 Sound Quality of Electric vehicles Etienne Parizet 1 , Karl Janssens 2 , Pedro Poveda-Martínez 3 , Andreia Pereira 4 , Jakub Lorencki 5 and Jaime Ramis-Soriano 3 1 LVA, INSA-Lyon, Villeurbanne, France, etienne.parizet@insa-lyon.fr 2 LMS International NV, Leuven, Belgium, karl.janssens@lmsintl.com 3 University of Alicante, Alicante, Spain, jramis@ua.es, pedro.poveda@ua.es 4 University of Coimbra, Coimbra, Portugal, apereira@dec.uc.pt 5 Politechnika Warszawska, Warszawa, Poland, j.lorencki@mechatronika.net.pl Abstract. Despite being an important step in the fight against environmental pollution, electric vehicles and hybrid electric vehicles present some doubts. The low level of noise emitted by the propulsion system implies an increased risk for pedestrians, especially at low speeds. The Competent Authorities, as well as the scientific community and industry, are addressing the problem to stablish a common legislative framework regarding road safety. The most significant proposal is the use of Acoustic Vehicles Alerting Systems (AVAS) in order to increase detectability of quiet vehicles. The aim of this chapter is to collect the main contributions regarding sound quality of hybrid electric vehicles and electric vehicles. As a started point, a state of arte is presented to contextualise the problem of quiet vehicles. Contributions included in this document refer to both inside and outside sound quality. 1 Introduction At low speed, electric vehicle are very quiet, when compared to gasoline or diesel engine cars. The noise level difference between an electric vehicle and one with an internal combustion engine can be as large as 6 dB(A) at 10 km/h [1,2]. This difference becomes smaller at higher speeds. Above 40 km/h (approx.), both types of cars are equally loud, as tires become the dominant noise source. This low noise level can be a safety issue for pedestrians, are they may not be able to detect an approaching EV, due to a strong masking effect of the ambient urban noise. This was confirmed by an in-situ experiment [3]: twelve visually impaired people had to detect an approaching car, driving on a very smooth road surface at a maximum speed of 30 km/h. At very low speed (10 km/h), EVs were detected only a few meters from the subjects. The real consequence on accident rates is still unclear, due to the reduced number of electric vehicles on the roads in the past years. In 2009, a study made by NHTSA [4] claimed that the incidence rate of pedestrian crashes was 0.9 %