Noise and its propagation in the observation area of the Makassar Strait Waters

Underwater noise has become a critical issue in oceanographic and marine ecological research because of increasing anthropogenic activities such as commercial shipping, offshore operations, and coastal infrastructure development. The Makassar Strait, a major international shipping corridor connecting the Pacific and Indian Oceans, is subject to intense vessel traffic that significantly contributes to acoustic pressure in the marine environment. This study quantifies and characterizes underwater noise levels in the Makassar Strait using in situ hydrophone measurements and acoustic spectral and statistical analyses conducted at 19 observation stations. The results indicate elevated sound pressure levels in proximity to the primary shipping lanes, with dominant acoustic energy concentrated below 1 kHz, consistent with large-vessel noise signatures. While propagation analysis suggests that the recorded noise levels do not exceed the temporary or permanent threshold shift criteria for marine mammals based on the NMFS (2024) guidelines, several locations exhibit high sound exposure levels that may increase the potential for behavioral disturbance and acoustic masking. These findings highlight the ecological significance of underwater noise in the Makassar Strait, and underscore the importance of incorporating acoustic considerations into marine spatial planning and environmental management strategies in Indonesian waters.