Ship Noise Characteristics in the Java Sea: A Preliminary Study on Underwater Noise Pollution in Indonesia

Indonesia is the largest archipelagic nation in the world, facing high environmental challenges due to underwater noise generated by activities from various types of ships. Therefore, this study aimed to examine the noise characteristics (specifically sound pressure level (SPL) and frequency) of different ships operating in the Java Sea, categorized by tonnage, namely under 30 GT, 30–100 GT, and exceeding 100 GT. Using a calibrated omnidirectional hydrophone system alongside synchronized video documentation, acoustic data were collected and analyzed to assess noise intensity, frequency, and duration. The results showed that small ships produced higher frequency broadband noise, with SPL ranging from 122 to 144 dB re 1 µPa based on speed. Medium-sized ships display dominant frequencies under 30 kHz, with SPLs related to engine power and operating speed. Large ships, such as ferries, tugboats, and patrol boats, show unique spectral profiles influenced by engine type, achieving SPL of approximately 155 dB re 1 µPa. This study showed the significant variability in underwater noise emissions based on type and operational behavior of ships, suggesting the need for noise mitigation strategies in marine policies to safeguard Indonesia's delicate marine ecosystems.