Underwater sound is modelled and mapped for purposes ranging from localised environmental impact assessments of individual offshore developments to large-scale marine spatial planning. As the area to be modelled increases, so does the computational effort. The effort is more easily handled if broken down into smaller regions that could be modelled separately and their results merged. The goal of our study was to split the Australian maritime Exclusive Economic Zone (EEZ) into a set of smaller acoustic zones, whereby each zone is characterised by a set of environmental parameters that vary more across than within zones. The environmental parameters chosen reflect the hydroacoustic (e.g., water column sound speed profile), geoacoustic (e.g., sound speeds and absorption coefficients for compressional and shear waves), and bathymetric (i.e., seafloor depth and slope) parameters that directly affect the way in which sound propagates. We present a multivariate Gaussian mixture model, modified to handle input vectors (sound speed profiles) of variable length, and fitted by an expectation-maximization algorithm, that clustered the environmental parameters into 20 maritime acoustic zones corresponding to 28 geographically separated locations. Mean zone parameters and shape files are available for download. The zones may be used to map, for example, underwater sound from commercial shipping within the entire Australian EEZ.
Report from workshop on characterising underwater shipping noise in Australia
The objective of the meeting was to present and discuss the initial results from the current project related to mapping of shipping noise. The meeting also provided an opportunity to discuss the future proposed project that will be extending this work and coordinate research with stakeholders and their management priorities to ensure the project delivers useful tools for management. Specifically:
Provide a brief overview of noise mapping projects overseas and the underlying management imperatives
Present preliminary findings of shipping noise maps from current NESP C5 project
Identify management priorities related to underwater noise by relevant stakeholders
Provide an overview of the future proposed NESP shipping noise project
Discuss future direction and development of noise maps for Australia