The concept of a MEMS-based acoustical sensor microarray cluster that can be used in a hearing instrument to improve speech intelligibility in a noisy reverberant environment has been presented. The proposed sensor microarray cluster has a cubic geometry where five identical MEMS-based microarrays of acoustical sensors constitute each side of a cubic and the bottom of the cube has been used for mounting and interconnection purposes. The steerable beams of each individual sensor microarray are used to be synchronized and polled using a microelectronic beam synthesis engine. In this way it will be possible to provide a three dimensional dynamic directionality for the sensor microarray cluster.The system can realize an improved dynamic directional speech acquisition system comparing to planar arrays for hearing instruments. The complete cubic sensor microarray cluster can be fabricated as a single die using Standard MEMS fabrication technology.