Apparatus and method of vehicle occupant sensing using multiple ultrasonic frequencies

The present invention relates to improvements in echo ranging vehicle occupant location sensing. An apparatus () determines a vehicle occupant location characteristic. The apparatus () includes at least one sensor (e.g., ) for echo ranging at first and second ultrasonic frequencies. A timer function portion () of a microcomputer () determines a time-of-flight for each frequency signal. The microcomputer () determines the occupant location characteristic using at least one of the determined times-of-flight.