In conventional ultrasonic testing (UT), a single-element probe emits an ultrasonic wave that penetrates the material. If the material has no defects, you will see a penetration echo at the beginning of the A-scan and an echo from the back wall of the material later in the A-scan. If the wave encounters a crack or other defect, the reflection echo appears earlier in the A-scan. Based on the timing and amplitude of this pulse in the A-scan, the operator can interpret the nature of the defect. This is time-consuming and requires a great deal of experience in operating the equipment and evaluating the results.