Optimum near-field performance of microphone arrays subject to a far-fieldbeampattern constraint

This article addresses the problem of maximizing the near-field gain of a m icrophone array subject to a constraint on the far-field beampattern. The p roblem arises when acquiring speech from a near-field talker in the presenc e of a strong source of interference located farther from the array. When t he angles of incidence from the near-field target and the far-field interfe rence are identical, enforcing a null constraint in the interference direct ion reduces array gain and robustness, This article shows how to mitigate t his effect by selection of the constrained response level. A suitable selec tion is to force the beampattern in the interference direction to be propor tional to the unconstrained beampattern. The proportionality constant can t hen be used to trade off interference reduction and array gain. Specific nu merical examples are provided. (C) 2000 Acoustical Society of America. [S00 01-4966(00)03711-1].