Simulation result of the effects of radiation noise from long-distance ships on marine mammals

Abstract

In recent, there is a worldwide concern that underwater noise from human activities may have impacted marine life. The international community recognizes the underwater radiated noise from navigational ships may have consequences on marine life. However, there is no scientific evidence for these, so they need to be investigated. MLIT launched the project with the aim of understanding the current status of underwater noise by navigational ships. In this project, a hydrophone has been installed in the sea off Ohshima Island since 2020 to measure the noise by navigational ships around the hydrophone. The purpose of this study , first is to calculate the source level of ship radiation noise using the normal mode method with the ship noise data obtained from hydrophone measurements. Second is to simulate the propagation of the source level using Parabolic Equation (PE) with the marine environment of the propagation path as a parameter. Finally, based on the results of propagation simulations, we examine the impact of ship noise on whales. As a result, revealed the noise levels emitted from RORO vessels, and by simulating the propagation of the noise levels, it was possible to confirm the distances that affect the whale's hearing.