Modified Sound Field Interpolation Method for Rotation-robust Beamforming with Unequally Spaced Circular Microphone Array

In this paper, we propose an improved method for interpolating a sound field to make it possible to use an unequally spaced circular microphone array (CMA) in rotation-robust beamforming. The previous method of sound field interpo-lation for rotation-robust beamforming required a regular CMA. This constraint causes degeneration when the microphones are non-uniformly spaced and makes the previous method difficult to utilize in practical applications. To address this issue, the proposed method first estimates the sound signal at equally spaced positions from that observed with the unequally spaced CMA after rotation and then performs a variant of the previous method to obtain the signal before rotation. A series of simulated experiments are conducted. The experimental results indicate that the proposed method avoids the adverse effects of unequal placement and shows a greater improvement in estimating the signal before rotation under different circumstances. Also, the proposed method significantly improves the performance of beamforming compared with the previous method.