Architectural criteria such as the type of building, floor plan design and the geometry and quality of the building envelope, as well as the structural design of the individual components, must be taken into account when planning noise protection. The trend in architecture to build spaces that are as open and brightly lit as possi ble places the focus on windows and glazing. DIN 4109 regulates the minimum sound insulation requirements in building construction and for windows and doors lays down six sound insulation classes.