Aspects of first‐order differential microphone arrays in the presence of sensor imperfections

Abstract

Abstract Array processing for broadband signals like speech is not a trivial task. Most sensor arrangements and the related beamforming algorithms show strong frequency dependent characteristics. Differential microphone arrays promise frequency independent high directional gain with compact arrangements. However, this type of microphone array has also the problem that even small deviations in microphone properties can cause severe degradation of the array's performance. Especially at low frequencies the achievable gain is limited by the influence of sensor mismatch and sensor noise.In this contribution the performance of first‐order differential arrays is examined and important parameters such as array response and directivity index are thoroughly studied. The frequency dependence of these parameters is investigated in order to derive limits for a favorable frequency range. First, the performance of the array is examined for ideal sensors. Then, two different models for sensor mismatch are introduced to describe the degradation of the array's performance. In addition, solutions for sensor calibration and experimental results with real microphones are presented.