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A study in beamforming and DAMAS deconvolution

Bosscha, A.J. (2013) A study in beamforming and DAMAS deconvolution.

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Abstract:Auroacoustic wind tunnel experiments are nowadays performed with phased array measurements. A large array of microphones captures data and together this data can be processed to gain insight the behaviour of the acoustic sources of the test subject. The regular way to proses this data is by conventional beamforming. Comparing the cross spectra of the microphones with a reference monopole source tells a lot of the acoustic sources the test object produces. Using this beamforming data in the DAMAS deconvolution method gives even better insight in acoustic behaviour. DAMAS deconvolution is an iterative method which can predict the locations of acoustic sources in a much better way than conventional beamforming. There are two possible ways to extract amplitude of sources out of conventional beamforming or DAMAS plots; using an integration method of using the peak levels of the plot. When investigating line sources, the peak level method gives an off result. The height of this off result seems to differ for various coherent lengths of the line source. A calibration function is made, which compensates for this off result, so the peak level method can also be used to find the strength of line sources. This calibration function is made for several coherent lengths. Also a method is discussed to extract coherence length out of experimental data. However, this can only be done on a visual manner, therefore the possibility of making an error is high. Due to this error in coherence length estimation, the wrong calibration value can be picked, which results in an error up to 2dB.
Item Type:Internship Report (Master)
USP - University of São Paulo, Brazil
Faculty:ET: Engineering Technology
Subject:52 mechanical engineering
Programme:Mechanical Engineering MSc (60439)
Keywords:Beamforming, DAMAS, Coherence, Line source, Peak levels
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