Abstract: An ultrasonic stroboscope is used to inspect an object rotating at a first frequency to determine if the rotating object has any defects. The ultrasonic stroboscope includes a first acoustic transducer spaced apart from the rotating object. The first transducer is configured to radiate ultrasonic energy at the rotating object at a second frequency. The second frequency is substantially related to a sub-harmonic of the first frequency so that the rotating object appears acoustically substantially still. A second acoustic transducer is used to sense a reflection of the ultrasonic energy from a defect in the rotating object. The second transducer translates the sensed reflection into at least one reflection signal. A user interface is coupled to the reflection signal.