ROTATING BEAMFORMING METHOD FOR THE USE OF TAILORED GREEN’S FUNCTIONS

Abstract

The localization of rotating sound sources using beamforming methods is of interest, for example, in the development of low-noise fans. There are various rotating beamforming methods in the literature, which can be divided into two groups. In the first group, the focus grid is rotated synchronously with the movement of the fan. The steering vectors of the stationary microphones are calculated as a time-dependent function. In the second group, the microphone array is virtually rotated with the fan. The steering vectors are usually calculated based on the Green's function of a monopole in free field. In practical fan applications, however, the sound propagation towards the microphones is often disturbed by obstacles such as the housing of a heat exchanger. A rotating beamforming method is presented, which can consider arbitrary, tailored Green's functions to calculate the steering vectors. In this paper, the Green's functions have been numerically simulated using the Fast Multipole - Boundary Element Method (FM-BEM). The method is validated using both synthetically generated data and data measured in the test rig for a rotating single sound source. Finally, the application on measured data of a fan is shown.