Characterising anthropogenic underwater noise to improve understanding and management of acoustic impacts to marine wildlife
This report examines the noise contribution of vessel traffic in Australian waters, with pristine marine soundscapes (dominated by natural, biological and physical sound) found to remain, particularly near offshore reefs and islands. Strong wind noise dominates the southern Australian coast. Underwater shipping noise dominates areas along the eastern seaboard and northwest shelf close to shipping lanes. A case study of humpback whales found noise models useful to investigate exposure levels on species of interest. Certain small non-AIS equipped vessels within a given size class and design type displayed significant differences in estimated source levels. Under specific conditions (e.g. channels, speed restrictions), Passive Acoustic Monitoring can provide estimates of small-vessel numbers in shallow water and assist in validating modelled exposure levels experienced by fauna. However, confidence is limited when multiple boats are present or where vessel behaviours vary significantly.