We developed a system for detecting the speech activity intervals of multiple speakers by combining multiple microphone arrays and human tracking technologies. We also proposed a method for estimating the face orientation of the detected speakers. The developed system was evaluated in two steps: individual utterances in different positions and orientations; and simultaneous dialogues by multiple speakers. Evaluation results revealed that the proposed system could detect speech activity intervals with more than 90% of accuracy, and face orientations with standard deviations within 30 degrees, in situations excluding the cases where all arrays are in the opposite direction to the speaker's face orientation.