Spot-forming method by using two shotgun microphones

Shotgun microphones and microphone arrays have super-cardioid polar patterns with a main lobe called "beam." This pattern suppresses noise located outside the beam, but it cannot suppress noise originating from the same direction as the signal. In this paper, we have proposed a "spot-forming" method using two shotgun microphones. Two shotgun microphones are first located in parallel, and then one microphone is rotated in order to make the beams intersect. This system suppresses all but the sound signals originating from the cross-point, by using the delay-and-sum beamformer. The experimental results showed that the proposed method could suppress noise located in front of or behind the target speaker, especially in the lower frequency band.