Large weapons, such as armor, artillery or demolitions, create a high-energy blast wave. It has 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. Mitigation measures need to be close to the source for best effectiveness, but due to the high sound pressure levels the interaction of the sound field with barriers and sound absorbing material cannot be described with a linear model. Therefore, the Netherlands Ministry of Defense and TNO, in cooperation with the US Army Engineer Research and Development Center and the University of Hull, have been investigating means to mitigate blast noise. A technique is presented which numerically propagates a blast wave over a barrier. Effects can be calculated up to several kilometers from the source. The technique has been validated with measurements with C4-explosives. For a series of barriers with blast absorbing material, e.g. gravel filled gabions, sound levels have been calculated behind the barrier. These levels are compared to sound levels without a barrier. The presented technique makes it possible to optimize a barrier design so that blast noise created by army training can be reduced.