iCity 1: imaF-Acoustics

Windows are one of the weakest elements of building envelopes, as they have to fulfil the most functions of all exterior building components. The most important functions that windows must provide are sufficient thermal insulation, fresh air and daylight in rooms as well as sufficient sound insulation to ward off noise from outside. For this reason, intelligent solutions should be used, which comply with the legal provisions for climate protection (Energy Saving Ordinance - EnEV) and the growing need for a quiet indoor environment (sound insulation requirements for external components), especially with the growing number of outdoor noise sources.

Since windows that are opened or tilted achieve very little sound insulation - at most a sound reduction index of 15 dB - even with highly sound-insulating glazing, an airtight facade would be an effective solution from an acoustic point of view. From an environmental point of view and for reasons of indoor air quality and comfort, however, this approach is not sensible, as this can only be achieved utilizing mechanical ventilation and air conditioning units. Therefore, the acoustic part of this project mainly deals with passive noise protection measures, especially for the low and medium frequency range, of so-called box-type windows (for example "Hafencity" windows as well as supply-air box-type windows).

Can windows be designed in such a way that when tilted open, they are simultaneously satisfactory from a ventilation and acoustic point of view? Does the controlled drive mechanism represent an additional noise source?

In the acoustic part of the research project, a parametric measurement series for sound insulation is developed using theoretical approaches and is carried out. Parameters include shell distance, degree of opening and the type and position of the absorbers in the window cavity. The window construction will be optimised in terms of sound insulation without losing sight of the ventilation properties. In addition, the sound power emitted by the drive mechanism is determined and possible reduction measures are recommended.

The aim of the acoustic part of the project is to achieve sufficiently high sound insulation of the tilted window with an innovative overall construction solution that does not diminish the ventilation properties.