Vertical description of the noise sources of a moving passenger car
PALLAS ; GAULIN ; BERENGIER
Type de document
COMMUNICATION AVEC ACTES INTERNATIONAL (ACTI)
Langue
anglais
Auteur
PALLAS ; GAULIN ; BERENGIER
Résumé / Abstract
Knowing the vertical position of vehicle noise sources influences the quality of traffic noise predictions and the evaluation of noise barrier efficiency. Two different methods leading to the vertical description of the vehicle noise emission will be presented. Both methods tend towards the global description of a passenger car by an equivalent point source located near the ground level. The first method (inverse fitting procedure) relies on acoustic propagation properties. It considers the vehicle as a unique point source. Two microphones are located at 7.5m and 13m respectively. It is based on a theoretical propagation model to calculate the excess attenuation between the two receivers. The source height is then adjusted to minimize the prediction/measurement difference. The optimum equivalent source height is found to lie between 1 cm and 5 cm. The second method uses a vertical linear array. The processing is based on the dedopplerisation and beamforming of the individual microphone signals. The technique is applied to the measurement of a passenger car, for various speeds, engine rpm and gears. The main noise source is detected near the ground under the car body. A second but much weaker source is located on the upper part of the front wheel, and can be ignored from the global equivalent description of the vehicle.
