Abstract
The categorisation of undersea noise as a source of pollution and as a potential threat to marine biodiversity by environmentalists began in the early 1990s in response to a coincidence of three focusing events. Namely: the shock testing of vessels by the US Navy; the transmission of up to 180 decibels of sound off Heard Island as part of the Acoustic Thermometry of Ocean Climate (ATOC) experiment; and the testing of low frequency active sonar by US, Australian, and NATO naval vessels. Less controversial, but arguably, no less serious, is undersea noise resulting from seismic surveys, dredging and construction activities, shipping, offshore wind farms, and sonar use associated with fishing and ocean science experiments.