An order-aware scheme for robust direction of arrival estimation in the spherical harmonic domain

Direction of arrival (DOA) estimation of sound sources using a spherical microphone array is usually performed in the spherical harmonic (SH) domain. In a non-noisy environment, it suffices to use only the zeroth- and first-order spherical harmonic beams (SHBs) in the SH domain for DOA estimation. One such method is based on the pseudo-intensity vector (PIV), which is attractive due to its low computational complexity. To improve the performance of the PIV method in reverberant environments, some methods have been proposed recently to further exploit high-order SHBs. However, these methods ignore the effect of noise on high-order SHBs, which may lead to poor performance in low signal-to-noise ratio (SNR) environments. To address the problem, this paper proposes an order-aware scheme that is able to select the high-order SHBs reliable for robust DOA estimation of multiple speech sources. Simulation and real-world experimental results demonstrate that the order-aware scheme based methods outperform their existing counterparts with less computational complexity in terms of both accuracy and robustness of DOA estimation. Moreover, the performance improvement is more significant in low SNR environment and in a scenario with small angular separation of sources.