Flaw detection is a of non-destructive testing technique based on the propagation of ultrasonic waves in the object or material tested. In most common ulrasonic applications, very short ultrasonic pulse-waves are transmitted into materials to detect internal flaws or to characterize materials. Ultrasonic testing is often performed on steel and other metals and alloys, though it can also be used on concrete, wood and composites, albeit with less resolution. It is used in many industries including steel and aluminium construction, metallurgy, manufacturing, aerospace, automotive and other transportation sectors.