Ears of the robot: Noise reduction using four-line ultra-micro omni-directional microphones mounted on a robot head

We propose a new type of noise reduction method suitable for autonomous mobile robots that require small and light-weighted devices and low-computational-cost algorithms. In the proposed method, four-line omni-directional micro electro mechanical system (MEMS) microphones are mounted on the robot head. The proposed method can reduce various kinds of noises simultaneously: directional noises are reduced by time-frequency masking using null beamformers and subtractive beamformers, and diffuse noises are reduced by multi-channel Wiener filtering using coherences. The effectiveness of the proposed method was shown in terms of speech recognition accuracies and speech qualities: the word error rate was reduced by 45% and 0.16 points of PESQ-MOS were improved compared with conventional time-frequency masking.