A system for monitoring a weld operation is provided. The system includes an ultrasonic wave generator adapted to deliver an ultrasonic wave to a target material during the weld operation and an ultrasonic receiver adapted to receive the ultrasonic wave propagated through the target material. The system also includes a signal processor adapted to determine a quality level of a weld created during the weld operation by extracting data corresponding to a torsional mode from the ultrasonic wave and comparing the data to a profile that corresponds to an acceptable quality level.