To identify sound source locations by using Near-field Acoustical Holography (NAH), a large number of microphone measurements is generally required in order to cover the source region and ensure a sufficiently high spatial sampling rate: it may require hundreds of microphones. As a result, such measurements are costly, a fact which has limited the industrial application of NAH to identify sound source locations. However, recently, it has been shown possible to identify concentrated sound sources with a limited number of microphone measurements based on Compressive Sensing theory. In the present work, sound radiation from the front face of a diesel engine was measured by using one set of measurements from a thirty-five-channel combo-array placed in front of the engine. The locations of significant noise sources were then identified by using two algorithms: i.e., l1-norm minimization and a hybrid approach which combined Wideband Acoustical Holography (WBH) and l1- norm minimization. It was found that both algorithms could successfully localize and visualize the major noise sources over a broad range of frequencies, even when using a relatively small number of microphones. Finally, comments are made on sound field reconstruction differences between the two algorithms.
Diesel engine noise, Source visualization, Nearfield acoustical holography, Wide band holography, L1-norm minimization
Acoustics and Noise Control
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