To determine whether a user is vocalizing while facing a microphone based upon a voice signal picked up by the microphone even when the position relation between the user and microphone changes.SOLUTION: For every frame, a vocalization-directional region is determined based upon a phase difference at every predetermined frequency between a first frequency signal and a second frequency signal, and a process of calculating a first phase difference deviation degree by which a phase difference at every predetermined frequency deviates from the vocalization-directional region is performed as many time as a plurality of frames. The first frequency signal corresponds to a first voice signal input to a first voice input part, and the second frequency signal corresponds to a second voice signal input to a second voice input part, A second phase difference deviation degree as a statistic of the plurality of frames is calculated from the first phase difference deviation degree of the plurality of frames, and when the second phase difference deviation degree is equal to or less than a first threshold, it is determined that a user is vocalizing facing the first voice input part and second voice input part.SELECTED DRAWING: Figure 9
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