This documentdraft European Standard describes calculation models designed to estimate the airborne sound insulation between adjacent rooms in buildings, primarily using measured data which characterize direct or indirect flanking transmission by the participating building elements, and theoretically derived methods of sound propagation in structural elements. A detailed model is described for calculation in frequency bands, in the frequency range 1/3 octave 100 3150 3 150 Hz according to EN ISO 717- 1, possibly extended down to 1/3 octave 50 Hz if element data and junction data are available (see Annex I); the single number rating can be determined from the calculation results. A simplified model with a restricted field of application is deduced from this, calculating directly the single number rating, using the single number ratings of the elements; a method to determine uncertainty is proposed for the simplified model (see Annex K). This document describes the principles of the calculation scheme, lists the relevant quantities and defines its applications and restrictions. It is intended for acoustical experts and provides the framework for the development of application documents and tools for other users in the field of building construction, taking into account local circumstances. The calculation models described use the most general approach for engineering purposes, with a clear link to measurable quantities that specify the performance of building elements. The known limitations of these calculation models are described in this document. Users should, however, be aware that other calculation models also exist, each with their own applicability and restrictions. The models are based on experience with predictions for dwellings; they could also be used for other types of buildings provided the construction systems and dimensions of elements are not too different from those in dwellings. The 2000 edition of this standard has been revised with greater details for application to lightweight constructions (typically steel or wood framed lightweight elements as opposed to heavier masonry or concrete elements). When the first versionedition of the standard was published, there was a necessity for giving tables of data; but now more experimental data are available, so some of these tables have been removed.