Design of robust nearfield wideband beamformers with optimum subband constraints

Design of nearfield wideband beamformers robust against microphone mismatches is of great interest in practical applications. The state-of-the-art design approach is based on the fullband processing. In this paper, the over-constraint problem suffered by the fullband design approach is studied, which typically leads to the undesired signal distortion with low-pass filtered characteristics. To combat the over-constraint problem, a new design approach for robust nearfield wideband beamformers with optimum subband constraints is proposed. The performance of the proposed design approach is evaluated and compared with the fullband design counterpart via design examples.

► The over-constraint problem suffered by the state-of-the-art fullband design is studied.
► The over-constraint problem can lead to the low-pass filtered signal distortion.
► The over-constraint problem will become more serious with the tap length increasing.
► A new design approach with optimum subband constraints is proposed to combat the over-constraint problem.
► The lowest bounds on the design parameters are derived for the proposed design approach.