Fraunhofer Institute for Building Physics IBP
Fraunhofer Institute for Building Physics IBP

Acoustic properties of modern thermal glazing

Acoustic properties of modern thermal glazing
© Fraunhofer IBP
Comparison of the thermal insulation and sound insulation properties of thermal glazing.

External noise is largely transmitted into buildings via windows and glazing. This is because they have poorer sound insulation properties compared to external walls and also due to the growing proportion of glass used in modern architecture.

Problems arise when planning sound insulation for buildings if manufacturers have the sound insulation of their products tested according to DIN EN ISO 10140 using only a normed installation surface and an aluminum-butyl edge seal. However, the sound insulation properties of glazing depend to a large extent on the pane format, the choice of warm edge spacer and other factors. When developing modern thermal glazing, the focus is increasingly on optimizing thermal insulation, while ignoring the consequences for sound insulation. The Building Acoustics Working Group at Fraunhofer IBP wants to change this.

Project goals

Planning sound insulation for windows and glazing is based on test certificates, which refer to a handful of isolated standard measurements in a test facility with two test rooms. Since the windows on the actual building site invariably have different dimensions, edge joints and restraints, their sound insulation properties on the building site differ from those stated on the test certificate. This difference increases if measurements are made from the outside to the inside. Therefore, on the basis of experimental tests, suitable planning tools need to be developed to simulate the effects of the format, spacers, gas mixture, etc.

The aim is to identify regularities in order to create a rule so that the sound insulation levels measured in compliance with the test standard can be adapted to the actual glazing used in practice. This can be accomplished using a suitable conversion equation or with the help of safety coefficients, which are published with a conversion software program or comprehensive table.

Current project status

Since purely theoretical calculations are often not accurate enough due to the acoustic conditions, a series of measurements of the narrowband airborne sound insulation is carried out first. In doing so, the structure of the panes is systematically varied. The focus of the tests is on modern, lightweight triple thermal glazing with an edge seal optimized to improve energy efficiency. The impact on the vibration behavior of the glass panes is also examined.

On completion of the measurements, the results are evaluated with regard to the variables that affect acoustics (pane type, area and aspect ratio). The format-dependent corrections derived from this are dimensioned in such a way as to obtain the best possible agreement between the measured and the calculated value of the weighted sound reduction index. The calculated parameters are then transferred to simulation software so that the sound insulation of further panes can be predicted in thirds.

Project partners

  • Saint-Gobain Glas Deutschland GmbH
  • Energy Glas GmbH