# Marine piling - energy conversion factors in underwater radiated sound: review

A report which investigates the Energy Conversion Factor (ECF) method and provides recommendations regarding the modelling approaches for impact piling as used in environmental impact assessments (EIA) in Scottish Waters.

## Figures

Figure 1. Back-propagated acoustic pulse energy against input hammer energy for measurements of offshore piling reproduced from Robinson et al. (2007)

Figure 2. Time snapshots of the stress wave down the pile and the radiated acoustic wave in the characteristic conical wavefront (Mach cone)

Figure 3. Plots of the horizontal component of the energy from the finite-element model by Zampolli et al. (2013)

Figure 4. SEL sound field reproduced from Dahl and Dall'Osto (2017)

Figure 5. Modelled (red) versus measured (blue) per-pulse SEL for four piles between 0.8 km and 3.8 km from the piling operations reproduced from Thompson et al (2020)

Figure 6. Point-source equivalent ECF calculated over the course of the piling sequence from back-propagated hydrophone measurements from Thompson et al (2020)

Figure 7. Example propagation loss (dB re 1 m²) from the geometric spreading equations for a point source in shallow water

Figure 8. Example transmission loss referencing the sound level at 100 m using the DCS model

Figure 9. Transmission loss referencing the sound level at 100 m calculated for a monopole point source and DCS model in 30 m water depth

Figure 10. Transmission loss referencing the sound level at 100 m calculated for a monopole point source and DCS model in 100 m water depth

Figure 11. Transmission loss referencing the sound level at 2 km calculated for a monopole point source and DCS model

Figure 12. Per-pulse SEL (dB re 1 µPa²s) sound field up to 1 km generated by the line-source model for the example scenario

Figure 13. Per-pulse SEL (dB re 1 µPa²s) sound field up to 10 km generated by the line-source model for the example scenario

Figure 14. Per-pulse SEL (dB re 1 µPa²s) as a function of distance. Results are shown for a receiver 2 m from the seafloor (z = 28 m), the depth-averaged level, and the DCS model matching levels at 10 m

Figure 15. Back-propagated energy source levels (dB re 1 µPa²m²s) using the modelled sound field from the line source and propagation loss calculations for the point source

Figure 16. Per-pulse SEL (dB re 1 µPa²s) sound field up to 1 km generated by the point-source model for the example scenario, with levels back-propagated using levels from the line-source model for a receiver at 100 m range and 28 m depth

Figure 17. Per-pulse SEL (dB re 1 µPa²s) sound field up to 10 km generated by the point-source model for the example scenario, with levels back-propagated using levels from the line-source model for a receiver at 100 m range and 28 m depth

Figure 18. Per-pulse SEL (dB re 1 µPa²s) sound field up to 10 km generated by the point-source model for the example scenario, with levels back-propagated using levels from the line-source model for a receiver at 170 m range and 28 m depth

Figure 19. Per-pulse SEL (dB re 1 µPa²s) sound field up to 10 km generated by the point-source model for the example scenario, with levels back-propagated using levels from the line-source model for a receiver at 170 m range and 28 m depth

Figure 20. Per-pulse SEL (dB re 1 µPa²s) as a function of distance for line and back-propagated point sources. Results are shown for a receiver 2 m from the seafloor (z = 28 m)

Figure 21. Depth-averaged per-pulse SEL (dB re 1 µPa²s) as a function of distance for line and back-propagated point sources

Figure 22. Energy source levels (dB re 1 µPa²m²s) calculated using the point-source equivalent ECF method for β = 0.5 % and β = 1.0 %

Figure 23. Per-pulse SEL (dB re 1 µPa²s) sound field up to 1 km generated by the point-source model for the example scenario, with levels calculated using a point-source equivalent ECF of 0.5 %

Figure 24. Per-pulse SEL (dB re 1 µPa²s) sound field up to 10 km generated by the point-source model for the example scenario, with levels calculated using a point-source equivalent ECF of 0.5 %

Figure 25. Per-pulse SEL (dB re 1 µPa²s) sound field up to 1 km generated by the point-source model for the example scenario, with levels calculated using a point-source equivalent ECF of 1.0 %

Figure 26. Per-pulse SEL (dB re 1 µPa²s) sound field up to 10 km generated by the point-source model for the example scenario, with levels calculated using a point-source equivalent ECF of 1.0 %

Figure 27. Per-pulse SEL (dB re 1 µPa²s) as a function of distance for line and point-source equivalent ECF model. Results are shown for a receiver 2 m from the seafloor (z = 28 m)

Figure 28. Depth-averaged per-pulse SEL (dB re 1 µPa²s) as a function of distance for line and point-source equivalent ECF model

Figure 29. Difference in the per-pulse SEL against distance from the pile between the line source model and the point-source equivalent ECF model using β = 0.5 % and 1.0 %

Figure 30. Modelled per-pulse SEL at 2 m above the seafloor for the point-source equivalent ECF models and the line-source model, against the measured results

Figure 31. Modelled depth-averaged per-pulse SEL for the point-source equivalent ECF models and the line-source model, against the measured results 2 m from the seabed

Figure 32. Drawing of monopile foundation (left) and jacket foundation with pin piles (right)

Figure 33. The difference between the measured and scaled results of the SEL at 750 m for all analysed piling locations, scaled with the parameters from piling at Hornsea

Figure A‑1. Physical model geometry for impact driving of a cylindrical pile

### Contact

Email: ScotMER@gov.scot

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