Exploring the efficiency of a source-level model to predict hydrophone-based received noise levels of the St. Lawrence Estuary’s merchant fleet

Abstract

The Enhancing Cetacean Habitat and Observation (ECHO) source-level model was statistically derived using nearly 10,000 vessel transits along Canada’s western coast. Before using this model in other areas, it is important to examine its efficiency in new environments and on other fleets. In this work, hydrophone-based acoustic recordings collected between August 3rd and September 16th of 2022 within the Saguenay-St. Lawrence Marine Park were used to investigate the applicability of the ECHO source-level model to Canada’s eastern fleet. Opportunistic transits of 71 merchant ships near (i.e., ≲3 km) the hydrophone were obtained. As an attempt to reduce computing times in the context of agent-based modeling, the reliability of the proposed analytic seabed critical angle (SCA) method for propagation losses calculations was examined and compared to robust, although time-consuming, numerical methods. Results generally show that the combination of the ECHO source-level model and our best estimates for propagation losses calculations does allow to reliably predict the acoustic footprint of the radiated noise levels by merchant ships in the acoustic module of the Marine Mammal and Maritime Traffic Simulator (3MTSim). However, computational gains could be marginal at best due to the analytic SCA method quickly becoming inconsistent with the numerical approach in range-dependent scenarios that often translate into long-range encounters.