Signal decorrelation by spatial smoothing for spherical microphone arrays

Spatial smoothing (SS) is a preprocessing technique that was shown to be efficient in decorrelating coherent signals thus making eigenstructure methods, like MUSIC, operative in a coherent interference environment. However, up to date the application of this technique to spherical arrays was not presented. The spherical array configuration provides desired 3-D symmetry and facilitates the estimation of both azimuth and elevation angles with the same accuracy. One of the approaches to perform SS is to construct arrays which are shifted versions of the original array. In this paper we investigate conditions on the locations of the shifted arrays to ensure efficient performance of SS, i.e. increase in the rank of the signals covariance matrix.