In the densely populated area of the Netherlands, the objective of the Netherlands Ministry of Defence is to find an optimal balance between military training and the impact on the surrounding civilian community. A special case concerns large weapons, such as artillery or demolitions, which create high-energy blast waves. These waves have a low frequency content, typically between 15 and 125 Hz, and can propagate over large distances. As a result it is a relative important cause for annoyance. The challenge is to determine accurately the acoustic source strength. This source is then used in a dedicated model for military training facilities, to calculate rating sound levels around the facility for different training situations and to calculate the effect of measures. This model uses a linear sound propagation and an equivalent linear source strength. The source strength is measured at a large distance, where the sound propagates linearly. As a consequence the ground and the meteorology have an important effect, and one has to correct for it. A more efficient approach has been tested, where the sound pressure measurements have been performed close to the source, at typically less than 10 meters distance. The linear source strength is then calculated by applying a non-linear propagation model. The results are compared to the conventional measurement method. Another advantage of applying the non-linear model, and the nonlinear source strength, is that the effect of mitigation measures close to the source can be determined.