Rotating dipole sources localization based on mode composition beamforming.

Rotating fans, propellers, and blades often generate aerodynamic noise with dipole-like radiation, making source localization important for noise diagnosis and reduction. Localizing these dipole sources using monopole-based rotating beamforming may produce artifacts. This paper proposes a dipole-based rotating beamforming for rotating dipole sources with unknown orientation based on mode composition beamforming, which imposes no constraints on microphone array placement, and is suitable for broadband sources with high rotating speed while maintaining high computational efficiency. This beamforming is obtained by combining three orthogonal dipole components based on the exact frequency-domain rotating-dipole solution, and then using a fast Fourier transform to efficiently compute modal transfer functions of three orthogonal dipole components. Numerical simulations demonstrate that the beamforming proposed in this paper eliminates the artifacts caused by monopole-based rotating beamforming. The experiment with a rotating propeller demonstrates the practical applicability of this beamforming.