Frequency-invariant beamformers are useful for spatial audio capture since their attenuation of sources outside the look direction is consistent across frequency. In particular, the least-squares beamformer (LSB) approximates arbitrary frequency-invariant beampatterns with generic microphone configurations. This paper investigates the effects of array geometry, directivity order and regularization for robust hypercardioid synthesis up to 15th order with the LSB, using three 2D 32-microphone array designs (rectangular grid, open circular, and circular with cylindrical baffle). While the directivity increases with order, the frequency range is inversely proportional to the order and is widest for the cylindrical array. Regularization results in broadening of the mainlobe and reduced on-axis response at low frequencies. The PEASS toolkit was used to evaluate perceptually beamformed speech signals.
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