Generalized Relative Harmonic Coefficients

In literature, sound source localization under the far- and near-field scenarios are mostly addressed as independent tasks using different approaches. This causes a tedious task to detect the type of soundfield, whereas in practice there may not be a clear boundary between the far- and near-field soundfield. In contrast, this paper proposes a multi-channel feature denoted generalized relative harmonic coefficients (generalized RHC) in the spherical harmonics domain, which can equally localize both far- and near-field sound source without requiring any adjustments. We derive the analytical expression of this feature and summarize its unique properties, which facilitate two single-source directional-of-arrival estimators: (i) using a full grid search over the directional space; and (ii) a closed-form solution without any grid search. Experimental study in realistic noisy and reverberant environments under both near-field and far-field conditions validates the efficacy of the proposed algorithm.