Considering the relative quietness of electric motors, tyre/road interaction has become the prominent source of noise emission from Electric Vehicles (EVs). This study deals with the potential influence of the road surface on EV noise emission, especially in urban area. A pass-by noise measurement campaign has been carried out on a reference test track, involving six different road surfaces and five electric passenger car models in different vehicle segments. The immunity of sound recordings to background noise was considered with care. The overall and spectral pass-by noise levels have been analysed as a function of the vehicle speed for each couple of road surface and EV model. It was found that the type of EV has few influence on the noise classification of the road surfaces at 50 km/h. However, the noise level difference between the quietest and the loudest road surface depends on the EV model, with an average close to 6 dBA, showing the potential effect of the road surface on noise reduction in the context of growing EV fleet in urban area. The perspective based on an average passenger EV in a future French or European electric fleet is addressed.

In both the current and foreseen context of significant development of the electric vehicle (EV) fleet, a future increasing ratio of EVs in the urban traffic is expected, still enhanced in low-emission zones involving bans or restricted access to other vehicles. EVs are known to be quieter than conventional vehicles at low speed because of a low motor noise emission, resulting in a higher prevalence of rolling noise in the environmental noise. EVs differ from conventional vehicles in several parameters that can influence tyre/road noise, like weight and torque. The LIFE E-VIA project objectives consist in developing, implementing and assessing a low-noise road surface for light EV traffic in urban conditions, optimised from an acoustical and life cycle perspective. In parallel, an optimisation of EV tyres is investigated. Prior to forthcoming layout in Florence (Italy) for assessment under real traffic conditions, a prototypal road surface has been implemented and evaluated on a test track in Nantes (France). Preliminary tests carried out with different EVs on several road surfaces highlighted the variability of noise emission over vehicle types and pavements, leading to specific ranking. Two prototype versions of a low-noise road surface have been laid out in Nantes, respectively without and with crumb rubber. Both of them have been acoustically assessed with on-board microphones (CPX method) and at roadside (CPB method and microphone array). Constant speed, acceleration and deceleration conditions were considered for pass-by tests. Other acoustical or physical parameters have been measured: acoustic absorption, 3D-texture, mechanical impedance and skid resistance properties (BPN and MPD). In comparison with a reference DAC 0/10 road surface, very usual in France, a roadside noise reduction up to 4 dB(A) was found at steady pass-by speed 50 km/h. Grip values are very high and macrotexture levels moderate. Lastly, mixtures durability is analysed with laboratory tests.

The I-STREET CUD-SF project aims at developing an urban pavement made of cement concrete slabs that can be easily removed and replaced for maintenance purposes. These slabs are made of a dense cement concrete body and a functionalized porous top layer ensuring water drainage and sound absorption. In order to optimize the porous layer for tyre/road noise reduction, several mix recipes with different porosity and maximum aggregate size were considered. Recipes with the most interesting absorption properties were preliminary selected based on absorption coefficient measurements performed on cylindrical test specimens with an impedance tube. A second phase was dedicated to evaluation of texture induced coast-by rolling noise levels with the tyre/road noise prediction model HyRoNE from 3D texture scans performed on rectangular laboratory samples. Finally, based on a porous medium model and a propagation model considering the tyre/road noise source as an omnidirectional point source over an impedance plane surface, the porous layer thickness of the selected mix was adjusted to minimize the predicted noise at roadside for different reference rolling speeds. This paper gives an overview of the results obtained at the different stages of the optimization process, prior in-situ assessment of the industrial solution in a near future.