A Differential Microphone Array with Input Level Alignment, Directional Equalization and Fast Notch Adaptation for Handsfree Communication

We revisit the standard differential microphone of [1] and propose three algorithmic enhancements. First, a simple alignment procedure equalizes the power levels of the input signals. Second, we describe an efficient algorithm to equalize the distorted directional response of the original algorithm. This enables a wider operating frequency range and helps to reduce the noise gain of the array. Third, a fast time-domain notch adaptation algorithm is presented to reliably track interfering sound sources. Its tracking performance is not impaired by the activity of desired sound sources. Finally, we describe a fixed-point arithmetic implementation of the modified algorithm for wideband handsfree communication (fs =16 kHz) using two miniature digital MEMS microphone capsules.