The Acoustic Observatories sub-facility manages the IMOS passive acoustic observatories, each of which comprises four moorings with sea noise loggers, hydrophones and associated mooring gear.  The passive acoustic sea noise loggers record sound emitted by natural processes in the ocean and underwater noise sources of biological origin, such as marine mammals, crustaceans and fish, which have unique acoustic signatures.  Through an analysis of these signals, it is possible to discriminate and identify different species and to assess the number of animals present within the range of acoustic observation, which can then be linked to ocean productivity.  Big animals can also be located by a horizontal array of sea noise loggers constituting a passive acoustic observatory.

Currently, there are three acoustic observatories in operation; the Perth Canyon array in Western Australia, the Portland acoustic array in South Australia and the Passive acoustic array off New South Wales.