| Summary: | Underwater noise is a by-product of marine industrial operations, that plays an increasing role in environmental impact assessments. It can have a variety of temporary to chronic bioacoustic impacts on marine fauna, such as behaviour modification, changes in habitat usage or migration, communication masking, and auditory and non-auditory physiological impacts. There are still lots of unknowns. Audiograms (curves of hearing sensitivity) have only been measured of few individuals of about 20 marine mammal species, and even fewer individuals and species of other marine genera. No audiograms exist for sperm whales or baleen whales. Behavioural responses likely depend on prior experience (habituation versus sensitisation), age, gender, health, context, current behavioural state etc., but we don’t understand the details or mechanisms. Data on hearing loss and acoustic trauma is even scarcer. Finally, what is the biological significance of individual acoustic impacts? Environmental agencies and regulators struggle for data to support environmental management. Research on the impacts of underwater noise is being undertaken around the globe, but there is a substantial delay in publication and science transfer. In the face of uncertainty, what is being done? This article aims to provide a brief overview of underwater noise regulation in Australia and overseas. Regulations vary from country to country. Some jurisdictions use specific do-not-exceed thresholds, which are very broadly applied across differing species and environments, and sound sources. Others use more conceptual requirements such as ‘minimising impact to acceptable levels’, yet what this means has to be defined and demonstrated by each proponent for their specific situation (i.e., operation, environment and organisms). Furthermore, in many situations, multiple differing Acts and policies apply.
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