The CNOSSOS-EU method is recommended in Europe for environmental noise prediction. In regards to road traffic, it includes vehicle noise emission models implicitly referring to internal combustion vehicles. The development of electrically driven vehicles calls for the future consideration of these vehicles in prediction models. On the basis of experimental data, the study reported in this paper proposes a noise emission model for extending CNOSSOS-EU to light electric vehicles. Correction terms to be applied to the propulsion noise component are determined. Investigations on a sample of tyres with good rolling resistance performance, which is a main tyre selection criterion on these vehicles, indicated that no correction is required for the rolling noise component. Differences between the noise emission from conventional vehicles and electric vehicles are discussed for several road surfaces. Owing to the limited vehicle sample as well as transitional statements, this new model for electric vehicles running at constant speed over 20 km/h should be considered as a first step towards the definition of this vehicle technology in CNOSSOS-EU

With the advent of electric vehicles and their significant lower propulsion noise emission it is possible to assess the tyre-road noise trough cruise-by measurements with an increased accuracy, even at speeds where a combustion engine propulsion system would usually disturb the measurement results. The European project FOREVER (Future OpeRational impacts of Electric Vehicles on European Roads) funded by CEDR between 2013 and 2014, aimed to provide data and information on the potential future noise impacts of electric vehicles (EVs) and hybrid electric vehicles (HEVs) on national roads, more specifically (i) the noise levels generated by electric/hybrid vehicles, (ii) how these vehicles can be effectively included in noise prediction models, and (iii) the likely noise impacts for residents as the number of electric/hybrid vehicles on national roads increases. Within work package 3 of the project, concerned with the noise emission of tyres used on EVs and HEVs, nine different sets of tyres have been selected and compared by carrying out pass-by measurements based on the standard ISO 11819-1. Special attention has been paid to potential and dedicated tyre sets which meet the demands for low energy consumption and a low rolling resistance to optimize the range of electric vehicles. The results have been analysed in order to reveal differences between single tyre sets and to quantify the influence of the tyres on the tyre-road noise. In a second part of the work, the EU tyre labels have been considered. The tyre labels have been introduced by the European Community for informing and helping consumers to choose products according to energy efficiency, safety in wet braking conditions and exterior rolling noise. Minimum requirements are also set in type-approval legislation. In the FOREVER project the exterior noise labels of the nine selected tyres have been compared with the results of the pass-by noise measurements performed on a common real-life road surface. Discrepancies observed on tyre ranking between both approaches have been discussed. Investigations within the concept of 'low-noise tyres' have been put forward accordingly. Finally, outcomes for the modelling of rolling noise from electric vehicles in the European noise assessment method CNOSSOS-EU, which is recommended for strategic noise mapping in Europe, have been given. As a complement to the EV propulsion noise component previously specified in the FOREVER project, it turns out that no correction term is required for EV rolling noise. In this paper, the main content as well as the outcomes of work package 3 of the project FOREVER are presented

In Europe, in situ measurements of sound reflection and airborne sound insulation of noise barriers are usually done according to CEN/TS 1793-5. This method has been improveds ubstantially during the EU funded QUIESST collaborative project. Within the same framework, an inter-laboratory test has been carried out to assess the repeatability and reproducibility of the newly developed method when applied to real-life samples, including the effect of outdoor weather variability and sample ageing. This article presents the statistical analysis of the inter-laboratory test results, and the values of the repeatability and the reproducibility,b oth in one-third octave bands and for the single-number ratings. The estimated reproducibility values can be used as the extended measure of uncertainty at the 95% credibility levelincompliance with the ISO GUM. The repeatability and reproducibility values associated with airborne sound insulation are also compared with the corresponding values for laboratory measurements in building acoustics and an acceptable agreement is found.

The boundary element method (BEM) is a widely used engineering tool in acoustics. The major disadvantage of the three-dimensional boundary element method (3D-BEM) is its computational cost, which increases with the size of the simulated obstacle and the simulated wave number. Thus, the geometrical details of the obstacle and the simulated frequency range are limited by computer speed and memory.The computational cost for simulating large obstacles like noise barriers is often reduced by applying the two-dimensional boundary element method (2D-BEM) on three-dimensional obstacles. However, the 2D-BEM limits the geometry of the boundary to obstacles with a one-dimensionally constant profile. An interesting compromise solution between the 2D-BEM and the 3D-BEM is the quasi-periodic boundary element method (QP-BEM). The QP-BEM allows the simulation of periodically repetitive complex three-dimensional structures and periodic sound fields while keeping the computational cost at a reasonable level.In this study, first, the QP-BEM was implemented and coupled with the fast multipole method. Second, the QP-BEM was used to simulate the sound field radiated by a simple geometric object, i.e., a uniformly vibrating cylinder. Results were compared to an analytic solution, for the evaluation of the numerical accuracy of our QP-BEM implementation. For the demonstration of some use cases, third, the QP-BEM was used to simulate the sound field scattered by a sonic crystal noise barrier and a noisebarrier top element. Keywords: acoustics, boundary element method, diffraction, fast multipole method, helmholtz equation, noise barriers, periodicity, scattering. INTRODUCTIONThe boundary element method (BEM) [1] is a widely used engineering tool to simulate the radiation, scattering, and diffraction of acoustic waves for a bounding geometry, i.e., the obstacle. Applications include the design of exhaust pipes, loudspeaker waveguides, virtual acoustics as well as noise barriers [2]. For instance, the BEM was used to investigate the acoustic properties of various noise-barrier materials and noise-barrier shapes, e.g., the general noise-barrier shape [3] or the design of noise-barrier top edges [4].The major disadvantage of the three-dimensional boundary element method (3D-BEM) is its computational cost, i.e., the required amount of physical memory (RAM) and the computation time. The computational cost increases with the size of the obstacle and the simulated wave number. For instance, the calculation of the standardized sound diffraction index (defined in the European standard EN 16272-4) of a noise barrier's top edge stipulates the simulation of a 10 m long and 4 m high noise barrier in third-octave bands ranging from 100 Hz to 5,000 Hz resulting in a numerical problem of approximately two million unknowns (when considering eight constant rectangular elements per wavelength in the simulation [5]). However, the available amount of RAM limits the number of unknowns in the numerical calculation and CPU speed defines the computation ...

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