The Scientific Committee on Antarctic Research (SCAR) convened its third international workshop on marine acoustic studies at the University of Cadiz, Spain in January 2006. The purpose of the workshop was to review improvements in knowledge and understanding of the interactions between marine mammals and noise generated by human activities in the Southern Ocean. The workshop revised the original risk assessments for particular acoustic equipment currently used in the Southern Ocean, e.g acoustic releases, bathymetric echo sounders, sub-bottom profilers and echo sounder arrays used for mapping krill. Mitigation procedures were discussed and a number of recommendations set for future activities and acoustic research in Antarctica. This paper provides a detailed report of the Cadiz workshop and is a supplementary information paper accompanying the SCAR Observer’s report “Report on the activities of the Scientific Committee on Antarctic Research (SCAR) 2005/06.” This report was originally delivered to the XXIX ATCM meeting in Edinburgh June 2006.