Ultrasonic vocalizations in mice have recently been widely investigated as social behavior; however, using existing sound localization systems in home cages, which allow observations of more undisturbed behavior expressions, is challenging. We introduce a novel system, named USVCAM, that uses a phased microphone array and demonstrate novel vocal interactions under a resident-intruder paradigm. The extended applicability and usability of USVCAM may facilitate investigations of social behaviors and underlying physiological mechanisms.