Maximum Noise Levels produced by light vehicles in relation with the radiated sound field

摘要

The determination of the sound levels radiated by individual vehicles to the receiver far-field position is important because if these levels exceed those allowed, actions to control the acoustic emissions should be taken. The work presented here combines near-field noise measurements from light vehicles with simulated transfer functions for modelling the propagation path to the far-field receiver position. An on-board electroacoustic system has been installed using a microphone situated close to the tire and a second microphone measuring the engine noise, in the proximity of the air intake system. The noise has been recorded through urban and suburban driving courses using petrol and diesel engines. Both types of vehicles have been engaged by five different drivers with the purpose of acquiring also measurements of the driving behaviour. The propagation path has been simulated using an analytical model assuming that the total noise contribution is due to the direct path coming from the noise source, and the noise reflected on the propagation surface, that has been studied using a one-parameter model or models depending on several parameters. The far-field radiation has been calculated considering either a uniform surface over the whole propagation path or a combination of different floors with discontinuity of impedances. The results obtained will be used for the identification of the drivers causing the highest noise levels responsible of the maximum annoyance.