Sensitivity is the ability of an ultrasonic system to detect defects at a given depth in a test material. The greater the signal that is received from these reflectors, the more sensitive the transducer system. Axial resolution is the ability of an ultrasonic system to produce simultaneous and distinct responses from indications Iocated at nearly the same position with respect to the sound beam.
Near surface resolution is the ability of the ultrasonic system to detect defects located close to the surface of the test piece. Typically, it is the minimum distance from the surface where a reflector has more than 6 dB resolution compared with the decay amplitude of the surface echo.
Similarly, the Far-surface resolution is the minimum distance from the back surface where the reflector can be resolved.