This European Standard describes a calculation model for the sound power level radiated by the envelope of a building due to airborne sound inside that building, primarily by means of measured sound pressure levels inside the building and measured data which characterize the sound transmission by the relevant elements and openings in the building envelope. These sound power levels, together with those of other sound sources in or in front of the building envelope, form the basis for the calculation of the sound pressure level at a chosen distance from a building as a measure for the acoustic performance of buildings. The prediction of the inside sound pressure level from knowledge of the indoor sound sources is outside the scope of this European Standard. The prediction of the outdoor sound propagation is outside the scope of this European Standard. NOTE For simple propagation conditions an approach is given for the estimation of the sound pressure level in informative annex E. This European Standard describes the principles of the calculation model, 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