Rusty steel cables, rotting concrete: every other road bridge needs to be renovated. An urgent problem. The sooner the damage is discovered, the easier it is to repair. With the help of a digital rapid test, scientists in Karlsruhe are looking for tired material. They measure the vibrations of the cables that give the bridge its tension. When the cables start to rust, there can be partial malfunction, and then they vibrate at a different frequency – like the strings of an out-of-tune violin. When this information is compared with other data, one can make precise statements about the condition of many bridges, stadium roofs, and wind energy facilities.