Acoustic propagation modelling shows the soundscape of the underwater environment. Models can predict the sound field generated by a source, or a series of moving sources, using computational algorithms to incorporate the interaction between complex environmental variables. Increasing regulatory requirements have prompted the need for high quality underwater sound modelling for industrial projects.
Seiche has collaborated with Plymouth University, the University of Bath and ZCAT Science Limited, combining their comprehensive knowledge of underwater sound propagation, computational algorithms and practical knowledge of the marine environment. The Seiche team specialises in modelling propagation of a seismic source over short-term cycles and has particular experience of working in Arctic waters, including dynamic river environments. The team provides a comprehensive range of services in underwater acoustic modelling.
Underwater propagation modelling
A wide range of dynamic variables influence how sound is absorbed, reflected and refracted within the water column and seabed layers. These include bathymetry, sediment stratigraphy, seasonality, conductivity, temperature, salinity, sea depth and water flow. Furthermore, to accurately image the soundscape, an understanding of temporal and spatial variation of these factors is essential. For the requirements of the project, we carefully consider:
- Short-term variation in local environments
- Long-term variation on regional scale
Sound source verification (SSV)
SSV is used to verify predictive modelling. Seiche’s range of field measurement techniques (including drift buoy, sub-sea recorder and digital hydrophone) work with further acoustic modelling to verify and refine expectations. Acoustic metrics include: sound pressure levels (SPL peak, peak-to-peak, root mean square – RMS) and sound exposure levels (SEL and cumulative SEL). SSV analysis may then factor in expected sensitivity levels of local marine life (typically based on parameters set out in Southall et al, 2007).
Mitigation zone determination (MZD)
SSV analysis may then factor in expected sensitivity levels of local marine life (typically based on parameters set out in Southall et al, 2007). Mitigation zones of appropriate size and shape are then determined based on the local conditions and environmental regulations in place.