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Entropy-based direction-of-arrival estimation methods for rigid spherical microphone arrays

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2019
Olgun, Orhun
Direction-of-arrival (DOA) estimation of sound sources is a popular topic of research and has an important role in several different applications including spatial audio. Recent advances in microphone arrays made more accurate sound field analysis possible. Spherical microphone arrays afford a trivial calculation of spherical harmonic decomposition of sound fields and can be employed in different DOA estimation methods in spherical harmonics domain. This thesis proposes a novel DOA estimation method called Hierarchical Grid Refinement (HiGRID) for rigid spherical microphone arrays (RSMA). This method is based on the calculation of the sector averaged directional response power of a steered beam over a sparse set of directions on the unit sphere. The selection of the direction for which response power is to be calculated is determined using spatial entropy as a criterion. A new clustering method based on connected components labelling is also proposed for counting sources and estimating their DOAs. In addition to HiGRID, this work investigates several state-of-the-art DOA estimation techniques. These include the improvement of DOA estimation performance or computational efficiency of Eigenbeam Multiple Signal Classification (EB-MUSIC) and Direct Path Dominance (DPD) test. HiGRID is first used as source counting method prior to EB-MUSIC to decrease the computational cost of DOA estimation. HiGRID is then used as a DOA estimation method following the DPD test which increases the DOA estimation accuracy while reducing the total computational cost. A new data-driven statistical method for DPD test threshold selection is also proposed. This allows the an informed selection of DPD test threshold based on effective rank statistics of spatial correlation matrices obtained from RSMAs. Comparison of HiGRID with previous DOA estimation methods with real and simulated recordings are presented. Evaluations of proposed algorithms for EB*MUSIC and DPD test are also presented in terms of DOA estimation errors using simulated recordings. HiGRID and its combinations with EB-MUSIC and DPD test performed favourably in comparison with other state-of-the-art DOA estimation methods indicating the utility of the proposed methods in DOA estimation.