Quality and comfort of private and public buildings is - to a considerable extent - assessed by the acoustic climate inside the building. Disturbing noise comes through windows, doors and lightweight internal walls with poor sound insulation capacity, especially at low frequencies. Disturbing reverberation and reflections are often present in public buildings with large areas of hard walls and ceilings, but also in private living rooms reverberation and reflections can severely prevent good music listening conditions. The increase of sound insulation of walls, windows and doors is essential in increasing the quality of the acoustic environment.