Accounting for sea floor properties in the assessment of underwater noise radiated from ships in shallow water

Abstract

To minimize the impact of human activities on marine fauna, efforts need to be taken to reduce underwater noise due to shipping by first defining procedures to measure radiated noise from ships. The signal received by a hydrophone array placed in the vicinity of the ship depends on the environment and the measurement con-figuration. For deep waters, standards have been published to estimate the noise source level taking into account the geometric losses and the effect of the surface. In shallow waters, underwater acoustic propaga-tion is influenced by the interactions with the surface and the sea bottom. Using numerical simulation, an empirical formula has been defined to correct the influence of the environment and estimate the noise source level. However, this empirical formula is only valid for sandy bottoms. The present work aims at correcting the formula to extend its validity to more types of sea bottom. Simulations are carried out using the open source codes: wavenumber integration in the low frequency range and beam-tracing in the high frequency range. The influence of shear waves in the sea floor is going to be investigated. Robustness of the empirical formula will be tested on different water depths and measurement ranges.