A new approach for estimating noise emission of automotive vehicles
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© S. Hirzel Verlag ¿ EAA.Current systems for measuring traffic noise are based on an overall assessment, so that they are unable to discriminate between type of vehicle and noise propagation. In this work we propose a near-field noise measuring method that is able to measure the contribution of each vehicle to the road traffic noise, allowing the characterization and quantification of different types of vehicles. This paper also describes a combination of analytical and experimental investigations for a methodology to carry out noise analysis for automotive vehicles. The system is based on two on-board microphones, one for the engine noise and the other for the rolling noise. In order to relate these near-field (0-0.1 m from the source) measurements with the noise radiated from the vehicle to the far-field (at 7.5 m from the source), a complete procedure was developed for the extrapolation of the near-field noise to the far-field positions with a combination of analytical models. Corrections for the extrapolated levels were made taking into account atmospheric factors, the spherical spreading term and the absorbing conditions of the propagation on the surface. For the microphone situated close to the engine it was also necessary to estimate the acoustic properties of the engine hood. Both noise levels were extrapolated independently of the far-field position, for which a noise level was predicted in order to estimate the remote noise impact to the overall traffic noise.