ISO 12354-4:2017 specifies a calculation model to estimate 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 document. The prediction of the outdoor sound propagation is outside the scope of this document. NOTE For simple propagation conditions an approach is given for the estimation of the sound pressure level in Annex E. ISO 12354-4:2017 describes the principles of the calculation model, lists the relevant quantities and defines its applications and restrictions.