Rotating beamforming – motion-compensation in the frequency domain and application of high-resolution beamforming algorithms

A method is presented for the location of rotating sound sources by a microphone array. In contrast to other methods which are formulated in the time domain, this method works completely in the frequency domain and allows the application of advanced, high resolution beamforming techniques. Following the work by Lowis and Joseph for ducted sources, it is shown that a generalized cross-spectral matrix in the rotating frame of reference can be calculated which can serve as a starting point for advanced beamforming techniques. The Green's function of a moving point source under free space conditions is expressed in spherical coordinates, which are, for numerical reasons, more convenient than cylindrical coordinates. The microphones on the array have to be arranged in a ring. As a practical example high resolution beamforming deconvolution methods are applied to simulated data and measured data from rotating sources.