With increasing marine traffic, the global level of anthropogenic noise is likely to rise. This might induce further stress to already endangered marine mammals, which rely on their acoustic senses for foraging, orientation and communication. The Southern Ocean provides an important habitat for marine mammals, both residential and migratory. To study its cetacean and pinniped populations as well as the ambient soundscape, autonomous underwater recorders were deployed on moorings in the Atlantic section of the Southern Ocean. Natural ambient noise is generated by the interaction of wind, waves, ice, biological and geological sources and subject to seasonal variations. Transient sounds such as whale and seal vocalisations strongly influence the acoustic spectra. Due to limited marine traffic and industrial activity the Southern Ocean contrasts regions with anthropogenic noise pollution on the northern hemisphere. This rather uninfluenced soundscape is analysed according to indicators as proposed under the European Union marine strategy frameworks directive. In this way a useful reference to the northern hemisphere oceans is given. The scope of anthropogenic and natural noise as well as sound examples will be presented.