The airborne and impact sound reduction of building elements are important quantities to compare the acoustic performance of products and to apply as input for prediction models for the acoustic performance of buildings. Besides using existing measurement methods, it is very useful to have the disposal of calculation models to predict these quantities for various types of elements from data on the design and materials used. Such models provide a quick and easy way to estimate the effect of changes in an element and to check for anomalies in measurement results. For homogeneous elements calculation models are given in an annex to EN 12354-1&2. These models will be discussed and possible extensions to layered, stiffened and double elements will be indicated. Such detailed models are used to give examples of acoustic behaviour of elements and estimations for single number ratings.