Metals have a distinctive sound when struck or tapped. This sound is referred to as the “sonarity” of the metal and is determined by the hardness and thickness of the material. Soft metals such as aluminum have a higher sonority than harder metals such as steel. The sonority of a metal is often used to identify it or to distinguish between different types of metal. For example, a blacksmith can often tell the difference between a wrought iron and a steel bar just by listening to their sound when struck.