Ultrasonic Testing is one of the most widely used NDE examination methods to inspect welds, bearing forgings, and components. Sound is introduced into the part using an ultrasonic transducer "probe" that converts electrical impulses from the UT machine into sound waves, then converts returning sound back into electric impulses that can be displayed as a visual representation on a digital or LDC screen. An experienced technician can determine the type of discontinuity like (slag, porosity or cracks) that caused the reflector. Because ultrasound will not travel through
air (atoms in air molecules are too far apart to transmit ultrasound), a liquid or gel called "couplant" is used between the face of the transducer and the surface of the part to allow the sound to be transmitted into the part. Many different types of UT inspection methods are available such as straight beam, angle beam, time of flight diffraction, through transmission, phased array, and immersion testing just to name a few.