Unattended sparse acoustic array configurations and beamforming algorithms

Various sparse array configurations have been studied to improve spatial resolution for separating several closely spaced targets in tight formations using unattended acoustic arrays. To extend the array aperture, it is customary to employ sparse array configurations with uniform inter-array spacing wider than the half-wavelength intra-subarray spacing; hence achieving more accurate direction of arrival (DOA) estimates without using extra hardware. However, this larger inter-array positioning results in ambiguous DOA estimates. To resolve this ambiguity, sparse arrays with multiple invariance properties could be deployed. Alternatively, one can design regular or random sparse array configurations that provide frequency diversity, in which case every subarray is designed for a particular band of frequencies. These different configurations are investigated in this paper. Additionally, we present a Capon DOA algorithm that exploits the specific geometry of each array configuration. Simulation results are presented to study the pros and cons of different sparse configurations.