Validation of dBSea’s 3D Parabolic Equation Solver
Coastal and nearshore environments with complex bathymetry present some of the greatest challenges for underwater noise assessments. These are also the locations where traditional 2D propagation models are most limited.
A 2D solver models sound propagation as a series of independent radial slices. As a result, it cannot accurately represent acoustic shadow zones—areas where islands, headlands, or other landforms block the direct transmission path and force acoustic energy to diffract around obstacles.
New research has validated the performance of dBSea V3’s 3D Parabolic Equation (PE) solver against real-world acoustic measurements collected at Tōtaranui, New Zealand. The study site includes Motu Ngārara Island, which creates a well-defined acoustic shadow zone, making it an ideal location for testing the capabilities of a full 3D propagation model.
Using more than 300 hours of field recordings from Interislander ferry transits, the study demonstrated that the 3D PE solver accurately reproduced measured sound levels within the acoustic shadow zone. In contrast, the legacy Nx2D approach is unable to simulate sound propagation into these regions and therefore provides no corresponding prediction.
Read the Full Paper
The validation study has now been published and is available online:
Implications for Marine Environmental Impact Assessments
The findings highlight the importance of selecting an appropriate propagation model when assessing underwater noise impacts. For projects located near islands, headlands, coastal embayments, or other bathymetric features capable of generating acoustic shadow zones, reliance on a 2D approach may result in significant underestimation—or complete omission—of noise exposure within these areas.
Where complex three-dimensional propagation effects are expected, 3D modelling is essential to provide robust and defensible impact assessments, ensuring that potential impacts on sensitive marine receptors are properly characterised.
