Theories And Methodologies Of The Multipole Beamforming

Aerodynamic noise causes severe problems in the development of modern industries,which not only brings noise pollution,but also damages the mechanical structures.Beamfoming is a popular microphone array processing technique in aeroacoustic measurements which usually depends on the monopole propagation characteristics in near field.However,most aeroacoustic sources have complicated directivity patterns.The conventional beamforming algorithms may lead to incorrect source locations and unexplainable source maps when applied to these sources.In this paper,a beamforming algorithm for localizing multipole sources with arbitrary directivity patterns is proposed.It eliminates the influence of directivity functions by modifying the cross-spectrum matrix and can accurately identify the source locations,strengths and orientations.Numerical simulations of dipoles and quadrupoles are elaborately setup to validate the capability.The experiment of realistic aeolian-tone dipole noise is also designed and a good performance of this algorithm on source identifications is observed.