Human activity in the aquatic environment generates underwater sound. This includes offshore construction for oil and gas platforms and wind farms, dredging, shipping, and military and other sonar or seismic surveys. The effects of such underwater sounds on marine life can range from very subtle behavioral reactions to physical damage and even death at very high exposure levels.
International bodies, such as the UN, advise regulations and frameworks to assess impacts and actually save marine life across the planet. Industries in Europe are required to perform Environmental Impact Assessments (EIA's) which may include modelling of the underwater sound. If a significant impact is discovered, they must work to minimise the sound exposure so as to not affect marine life. Outside of Europe, for example in the U.S., the Marine Mammal Protection Act – requires developers and planners to consider and manage sound-related impacts.
RISK ASSESSMENT FRAMEWORK FOR SOUND-RELATED IMPACTS
DHI has extensive experience in advising industry and policy makers on noise-related issues. Based on this, our experts offer risk assessments that represents a systematic approach to sound impact studies. We can also advise you on the impacts that have to be considered very early in the project phase.
Depending on your project plans, the sound that is generated will vary widely. DHI references a large database of all possible aquatic sound sources and can provide detailed information on the characteristics of the sounds generated by your project. This will help you target the Environmental Impact Assessment (EIA) to the issues at hand and will save time when consulting with regulators and stakeholders on possible impacts.
COMBINING BIOLOGICAL EXPERTISE WITH ACOUSTIC MODELING
What is most unique about DHI's approach is the integration of biological expertise with advanced modelling capabilities. This enables us to provide a more realistic exposure assessment. We use underwater acoustic modelling to calculate sound ranges and sound maps showing the distribution of the sound field in the study area and beyond. Sound maps are used in conjunction with data on the distribution and abundance of fish and marine mammals to provide an estimate of the number of individuals affected. The impact is then extrapolated using empirical data on hearing sensitivities and demonstrated effects.
DYNAMIC RISK ASSESSMENT OF ACOUSTIC DISTURBANCE
At DHI, we also develop agent-based models which take into account the movements of mammals before, during, and after noise exposure. This tool can be used for large scale risk assessments in new development areas (for example, oil exploration blocks). A variety of scenarios using a number of sound sources and disturbances can be modelled to identify especially risky periods or areas where impacts could be high. This can greatly increase the amount of information used for planning and decision making.
Optimized design of marine structures can further reduce sound-related impacts on the marine environment. Considering these impacts in the design stage of marine construction projects will strongly support the consenting process. Such green designs will minimize the environmental footprints and thereby benefit the marine inhabitants.