Although the Beamforming for moving sources is applied successfully to locate and to analyze noise sources at airplanes and trains, there are only a few papers where this technique is applied to cars. The present paper deals with the methodology that is neccessary to perform pass-by measurements on cars using microphone array technique and beamforming algorithms. In a first step, simulations were performed to determine the parameters required to carry out the intended measurements. Based on the results from the simulations, a 56-microphone array with 28 additional microphones, located on 8 external arms attached to the center array, was chosen because it obtained better noise source separation than other arrays evaluated. This array should be located at a distance of 5 m of the pass-by line, with a vertical distance of 1.5 m between the center of the array and the gound in order to separate the noise source from its image source. To process the data obtained from the measurements a moving focus algorithm was chosen, as it obtained better noise source separation than the fixed focus algorithm. The evaluation of the spectra showed a common spectrum trend independent from the tyre. This trend consists of a peak around 1 kHz with a decrease of the sound pressure level when the frequency is increased. Through the noise source maps the location of the noise source was calculated in the pass-by of the car near the center of the tread, identifying also higher emission from the front of the tyre than from the rear. A comparison between the results from the present study with those from other researches found in the literature shows a good agreement. Thus, it is possible to conclude that the methodology proposed is suitable for noise source identification during the pass-by of cars.
Methodology for pass-by measurements on cars with beamforming
2014
18 Seiten, 16 Bilder, 22 Quellen
Conference paper
Storage medium
English
Strahlformung , Rauschquelle , Separation , Fixfokus , Flugzeug , Mikrophon , Schalldruck
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