Humans and their activities in the marine environment introduce noise into the ocean in various ways. Each activity that generates noise may have different effects, depending on the noise generated, and its frequency, intensity and composition (intermittent, pulsed or continuous sounds).
The main anthropogenic activities producing high levels of noise are seismic surveys of sub-bottom strata (usually using air-gun arrays), active sonars (military, scientific surveying, echo sounders), explosions (associated with military exercises and port construction), pile-driving (wharf construction, offshore platforms), vessels (particularly dynamically positioned vessels), dredging and drill rig activities. Lower levels of noise are produced through general ongoing vessel activity and offshore renewable energy operations. To date:
- seismic surveys have been concentrated in the main oil and gas regions of the North West Shelf and Bass Strait (Figure MAR18)
- military sonar has been concentrated in maritime exercise areas such as Sydney and Perth
- dynamically positioned vessels are associated with offshore facilities
- pile-driving and dredging associated with port development have been concentrated in the north-west and north-east, although dredging activities are routinely conducted in port environs throughout Australia (see the Coasts report for further detail).
Because of the extent of marine activities generating noise in the marine environment, anthropogenic noise is considered to have high impact.