Subsea Acoustics and Vibration Measurement
Xi Engineering use numerical models to calculate the propagation of underwater noise produced by these activities for Environmental Impact Assessments (EIA). Xi can also provide third-party assessment of underwater noise chapters in marine EIA.
Xi use COMSOL Multiphysics and bespoke underwater noise propagation code written in Matlab to calculate the far-field sound level produced by underwater activity. These models consider the effect of the three-dimensional bathymetry and seabed type on the sound propagation. A particular strength of Xi is the ability to calculate cumulative sound levels produced by a range of sources located at different geographic positions. An example is the sound associated with the laying of HVDC cable where the concurrent sources may include trenching, marine vessel noise and multibeam echosounder all occurring at different locations. A further example is piling for offshore wind farms where several foundations may be piled concurrently over a large geographic area.
Xi is a world leader in the calculation of operational noise from tidal turbine arrays. The operational noise provides a vital early warning to marine animals that helps them avoid potentially fatal collision with the turbine’s moving parts. The designs of tidal turbines are rapidly evolving and it is often impossible to measure the acoustic output of the devices before they are placed into environments where they interact with marine animals. The integration of ambient noise measurements with acoustic modelling is used to predict the range at which marine mammals can detect tidal turbines. The output of the work can be used for Environmental Impact Assessments concerning the risk of marine mammal collision.