Linear Microphone Array Parallel to the Driving Direction for in-Car Speech Enhancement

This paper proposes a linear microphone array parallel to the driving direction for in-car speech enhancement. In contrast to other linear microphone arrays in the car cabin reported in a literature or implemented as a commercial product, the array axis is arranged in parallel to the driving direction. Thanks to the 90°-rotated array axis with the constraints on the microphone position specific to the car environment, a mirror image of the directivity toward the talker with respect to the array axis is no longer projected in the direction of interference and redirected to a direction with no interference. As a result, the talker speech can be discriminated from the interference by directivity, leading to good interference reduction with little speech distortion. Simulation results with signals recorded in a car environment show that the proposed linear microphone array with the array axis parallel to the driving direction has a null in the direction of interference, which leads to 13% higher word accuracy than the conventional microphone array with the array axis perpendicular to the driving direction.