Microphone arrays and beamforming have become a standard method to localize aeroacoustic sources. Deconvolution techniques have been developed to improve spatial resolution of beamforming maps. The deconvolution approach for the mapping of acoustic sources (DAMAS) is a standard deconvolution technique, which has been enhanced via a sparsity approach called sparsity constrained deconvolution approach for the mapping of acoustic sources (SC-DAMAS). In this paper, the DAMAS inverse problem is solved using the orthogonal matching pursuit (OMP) and compared with beamforming and SC-DAMAS. The resulting noise source maps show that OMP-DAMAS is an efficient source localization technique in the case of uncorrelated or correlated acoustic sources. Moreover, the computation time is clearly reduced as compared to SC-DAMAS.

The possibility of using the time-reversal technique to localize acoustic sources in a wind-tunnel flow is investigated. While the technique is widespread, it has scarcely been used in aeroacoustics up to now. The proposed method consists of two steps: in a first experimental step, the acoustic pressure fluctuations are recorded over a linear array of microphones; in a second numerical step, the experimental data are time-reversed and used as input data for a numerical code solving the linearized Euler equations. The simulation achieves the back-propagation of the waves from the array to the source and takes into account the effect of the mean flow on sound propagation. The ability of the method to localize a sound source in a typical wind-tunnel flow is first demonstrated using simulated data. A generic experiment is then set up in an anechoic wind tunnel to validate the proposed method with a flow at Mach number 0.11. Monopolar sources are first considered that are either monochromatic or have a narrow or wide-band frequency content. The source position estimation is well-achieved with an error inferior to the wavelength. An application to a dipolar sound source shows that this type of source is also very satisfactorily characterized.

Microphone array associated to signal processing technique such as beamforming is an efficient tool to localize acoustic sources. In an open wind-tunnel, the microphone array can be set below, above or on the side of the flow. The microphones are spatially distributed over a two-dimensional (2D) plane and the geometry may be regular, circular or a spiral shape. For each case, the scan zone where the potential source positions are searched is a plane parallel to the microphone array. In this study, beamforming and several microphone array techniques (Clean-SC, L1-GIB, DAMAS and SC-DAMAS) are compared in the case of two and three-dimensional (3D) scan zones. The microphone array techniques are compared in terms of position detection, source level estimation and computation time. The cases of a 2D scan zone, either parallel or perpendicular to the microphone array, are investigated. Then, the performances of each technique are studied in the case of 3D scan zone with a single or two microphone arrays. SC-DAMAS provides the best noise source map at the expense of a large computation time if the number of scan point is large. Clean-SC is a good tradeoff between fast computation and correct source detection. The second microphone array improves the noise source map provided by L1-GIB with a reasonable computation time.