The purpose of the research in this area is to understand and to be able to describe the propagation of sound waves in air, water and in solids. The centre of gravity of the research lies in the area of hydroacoustics and includes, for example, work for the Swedish Armed Forces on the development of reconnaissance systems and methods for submarine hunting, port protection, mine clearance and underwater communication. The advanced models developed in the course of this underwater research can also be applied to sound propagation in air from various types of noise sources, for example explosions and wind generators. The understanding of sound propagation in solid materials can be applied to the reduction of submarine acoustic signatures, seismic prospecting technology and the classification of buried objects.