Noise source identification with Beamforming in the pass-by of a car

Traffic noise is the most important environmental noise source. Standardized methods do not identify the main noise source or center an area of the car to do a more specific analysis. Other measurement techniques locate the noise source but have the problem of how to position the transducers to measure the noise sources during a pass-by. The best technique seems to be near-field holography (NAH), but it is only adequate at low frequency. In this paper the application of Beamforming for pass-by measurements has been considered. This technique allows not only to locate the main noise sources during the pass-by of a car, but also their characterization in terms of source strength. In order to test the accuracy of Beamforming in this kind of measurements, some pass-by measurements have been carried out, comparing the results obtained with other in the literature using different measurement techniques. Once the main noise sources are identified, a detailed analysis has been performed over sectors containing these noise sources, obtaining their acoustical characteristics, such as their spectra, sound pressure level, their dependence on the gear, the speed or the Strouhal number.