FIR-based symmetrical acoustic beamformer with a constant beamwidth

Abstract

Traditional beamformer design methods suffer from a frequency varying beamwidth, making them less effective for wideband applications. Existing approaches that try to solve this problem demonstrate degraded beamformer performance in terms of sidelobe level attenuation and sensitivity, making them less robust to interference and array attribute perturbations. Another common issue for existing approaches is high computational complexity, resulting in the ability to implement these approaches only for small microphone arrays, directly affecting the beamformer spatial resolution. In this paper, we introduce a new approach for designing a constant beamwidth beamformer. The proposed approach utilizes custom-tailored finite impulse response (FIR) filters for each microphone channel, manipulating the beampattern to achieve a desired beamwidth. The manipulated beampattern has approximately a constant beamwidth over a wide frequency band. Additionally, a post-summing output normalization filter is used to ensure a frequency invariant gain of the beampattern. By exploiting the physical microphone array configuration and attributes, we shape accordingly the frequency response of the FIR filters and control the beamformer beamwidth. The proposed approach demonstrates improved array response results in various scenarios, compared to available methods in the field, especially in terms of sensitivity to parameters mismatch, noise robustness and sidelobe attenuation.