The vehicular monitoring system obtains audio information from the speech of occupants within the vehicle and then processes that audio information to extract information about the behavior of the vehicle occupants. The pad has a current injector electrode and a current return electrode electrically isolated from each other and mounted on a face of the pad. The electronic circuit unit is therefore able to use fewer number of pads to provide an increased number of operating mode settings, with the benefit of reducing layout space on circuit board. The switch connects or disconnects the reference capacitor with a sensing capacitor.