Exterior-interior 3D sound field separation using a planar array of differential microphones

Sound field separation using spherical microphone arrays was recently introduced and has many applications, however, it is inconvenient to implement in realistic environment. In this paper, we propose a solution to separate 3D interior and exterior sound field by using a planar array of differential microphones. The even coefficients and odd coefficients of sound fields are separated in two different ways due to the properties of associated Legendre functions. Simulation shows this practical geometry has a good performance on interior and exterior sound field separation in both noiseless and noisy environments. We also evaluate the reconstruction accuracy of separated sound fields on different spherical surfaces.This work is supported by Australian Research Council Discovery Grant DP180102375 and the China Scholarship Council with the Australian National Universit

Spatial dissection of a soundfield using spherical harmonic decomposition

A real-world soundfield is often contributed by multiple desired and undesired sound sources. The performance of many acoustic systems such as automatic speech recognition, audio surveillance, and teleconference relies on its ability to extract the desired sound components in such a mixed environment. The existing solutions to the above problem are constrained by various fundamental limitations and require to enforce different priors depending on the acoustic condition such as reverberation and spatial distribution of sound sources. With the growing emphasis and integration of audio applications in diverse technologies such as smart home and virtual reality appliances, it is imperative to advance the source separation technology in order to overcome the limitations of the traditional approaches. To that end, we exploit the harmonic decomposition model to dissect a mixed soundfield into its underlying desired and undesired components based on source and signal characteristics. By analysing the spatial projection of a soundfield, we achieve multiple outcomes such as (i) soundfield separation with respect to distinct source regions, (ii) source separation in a mixed soundfield using modal coherence model, and (iii) direction of arrival (DOA) estimation of multiple overlapping sound sources through pattern recognition of the modal coherence of a soundfield. We first employ an array of higher order microphones for soundfield separation in order to reduce hardware requirement and implementation complexity. Subsequently, we develop novel mathematical models for modal coherence of noisy and reverberant soundfields that facilitate convenient ways for estimating DOA and power spectral densities leading to robust source separation algorithms. The modal domain approach to the soundfield/source separation allows us to circumvent several practical limitations of the existing techniques and enhance the performance and robustness of the system. The proposed methods are presented with several practical applications and performance evaluations using simulated and real-life dataset