Design and analysis of second-order steerable differential microphone arrays

Second-order differential microphone arrays (DMAs) are one of the most commonly used DMAs in practice due to the sensitivity of higher-order DMAs to microphone mis-matches and self-noise. However, conventional second-order DMAs are non-steerable with their mainlobe orientation fixed along the array end fire direction, which are not applicable to the case where sound sources may move around a large angular range. In this paper, we propose a design of second-order steerable DMAs (SOSDAs) using seven microphones. The design procedure is discussed, followed by the theoretical analysis on directivity factor and white noise gain of the proposed SOSDAs. Numerical examples are shown to demonstrate the effectiveness of the proposed design and its theoretical analysis.