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

Ship Noise Characteristics in the Java Sea: A Preliminary Study on Underwater Noise Pollution in Indonesia | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Ship Noise Characteristics in the Java Sea: A Preliminary Study on Underwater Noise Pollution in Indonesia Amron Amron, Rizqi Rizaldi Hidayat, Iqbal Ali Husni, Dyahruri Sanjayasari, and 3 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6624854/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract 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. ship noise Java Sea sound pressure level frequency sound duration Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction As the largest archipelagic nation in the world, Indonesia has significant potential for marine resources that is unparalleled. This nation has over 17,000 islands, showing substantial opportunities across multiple sectors, including fisheries, mining, shipping, tourism, defense, and the maritime industry. Particularly, fisheries resources serve as a fundamental pillar of the national economy that supports the livelihoods of many individuals for income and sustenance. Despite the significant potential, Indonesia faces environmental challenges that must be addressed, particularly related to the detrimental impacts of noise generated by various economic activities underwater. This noise pollution is recognized worldwide as a threat to aquatic ecosystems and the long-term sustainability of the resources (Gullett, 2022 ). Shipping activities, which include several operations such as fishing, cargo transportation, and marine tourism, are primary sources of noise pollution in water of Indonesia. Previous studies have shown that several factors contribute to the variations in sound characteristics produced by ships, such as size, the materials used in construction, engine power, and operational speeds (McKenna et al., 2012 ; Santos-Domínguez et al., 2016 ; Soares et al., 2020 ). The noise generated by these ships disrupts the comfort of individuals at sea, posing significant negative impacts on marine biota, which plays a crucial role in maintaining the health of aquatic ecosystems. For example, low-frequency sound emitted by ships can propagate over long distances beneath the water surface, potentially interfering with the communication patterns and behaviors of various marine species (Amron, et al., 2021 a). The impacts of anthropogenic noise on marine biota have increasingly become the subject of extensive studies within the scientific community. Several studies have shown that the noise produced by ships can induce stress responses in marine mammals and fish, leading to significant alterations in their behaviors related to foraging, social interactions, and reproductive activities (Kight & Swaddle, 2011 ; Rolland et al., 2012 ; Wright et al., 2011 ). In addition to the behavioral changes, the physiological repercussions of noise can disrupt essential bodily functions, causing modifications to feeding patterns, growth rates, and reproductive success, which contribute to a decline in the populations of certain species (Halliday et al., 2017 ; Nabe-Nielsen et al., 2014 ). This underscores the critical importance of understanding and effectively managing the impacts of noise generated by shipping activities essential for preserving marine ecosystems. Despite numerous studies, there is still limited information on the impact of noise generated by ships operating in Indonesian waters. For better understanding, extensive investigation is required to examine the characteristics of noise emitted by various types of ships in terms of frequency and intensity. The sound produced by ships is not always the same and changes due to many reasons such as size, engine power, and speed of movement. Smaller ships with engines that go faster usually make sound with higher frequency, while larger ones make lower type of frequency (Brooker & Humphrey, 2016 ; McKenna et al., 2012 ). Extra noise can also come because of engine operation, the spinning propeller, and the moving of ships in water which is called hydrodynamic impact (Ghaemi & Zeraatgar, 2022 ; Taskar et al., 2016 ). When noise occurs for a long period, serious impacts can happen to biota in the water. This is because different species in water do not have the same ability to handle sound. Some species have the ability to adjust a little, but others are showing strong problems with noise (Popper & Hawkins, 2016; Soares et al., 2020 ). Therefore, more investigations must be performed on how different ships create sound and its impact, especially in Indonesia. This kind of understanding is needed because water sound situation depends on type of ship. Based on the background above, this study aimed to examine the noise characteristics, including frequency and intensity of ships operating in the Java Sea, Indonesia. By exploring these dimensions, the results are expected to enhance the understanding of the impacts of noise on aquatic ecosystems and marine biota. Furthermore, the results are anticipated to serve as a reference for developing more effective policies regarding the management of fisheries resources and the protection of Indonesia's aquatic environment. When insight is gained, strategies can be identified to mitigate the adverse impacts of noise on marine life. The information is particularly crucial, as the sustainability of fisheries resources and the overall health of aquatic ecosystems rely on maintaining a balance between human activities and the survival of marine species. Therefore, this study holds significance for advancing scientific knowledge and informing policy-making that promotes the sustainability of fisheries resources in Indonesia. Material and Methods Noise generated by various types of ships with different tonnages was recorded in the Java Sea using a calibrated omnidirectional hydrophone (Sea Phone SQ26-08). The research was conducted in specific locations around Jepara (30–100 GT and over 100 GT), Semarang (under 30 GT and over 100 GT), Pekalongan (under 30 GT), and Tegal (under 30 GT and 30–100 GT) during August 2023 and April 2025 (Fig. 1 ). The study sites were characterized by shallow depth and muddy seabed. To capture the acoustic data, hydrophone was strategically deployed on study ship, positioned approximately 1.5 meters below the sea surface, effectively functioning as a surface-based system. This hydrophone boasts a sensitivity of -194 dB re 1 V.µPa⁻¹, a flat response ranges from 20 Hz to 45 kHz, and a gain of 25 dB. It was connected to a sound recorder capable of 16-bit recordings at a sampling rate of 44,100 Hz, with all audio files saved in WAV format. In comparison, ships navigating through the study location was documented using a high-definition CCTV camera with a resolution of 1080 MP. Sound and video recordings were synchronized and connected to a Zoom H1n digital recorder, allowing for real-time monitoring and observation on an LCD display. Information regarding engine size and type was obtained from the ship owner and crew, while the ship's operational speed was recorded using a vehicle speed radar detector. This full setup was not only for catching the noise from the ships but also was giving pictures, enhancing the analysis of the acoustic environment. The integration of advanced recording technologies and strategic positioning facilitated a thorough investigation into the impact of maritime activities on underwater soundscapes. The sound recording file in *.wav is initially opened in Audacity for processing before analysis in MATLAB. For data preparation, noise removal is applied with a high-pass filter where the cutoff frequency is set at 1 kHz. After step this, waveform analysis is performed to extract key parameters such as intensity, frequency, pulse duration, and interval duration. Waveform analysis is then conducted to determine parameters such as intensity, frequency, pulse duration, and interval duration. Sounds S ( t ) were recorded in volts and then converted to sound pressure, P ( t ) in µPa based on the time-domain ( t ). This was conducted using the following equation: $$\:P\left(t\right)=S\left(t\right)\times\:{10}^{\frac{-G}{20}}\times\:D\times\:{10}^{\frac{-SH}{20}}$$ RL ( t ) in dB re 1 µPa \(\:=20\text{log}P\left(t\right)\) , where G (in dB) represents the recorder gain (set at 25 dB), D is a constant reflecting the dynamic response of the recorder (1.4 V for this specific model), and SH denotes the sensitivity of the hydrophone. Additionally, the type of ships responsible for generating the noise is analyzed using video recordings, providing further context to the acoustic data collected. This combined approach allows for a comprehensive understanding of the acoustic environment influenced by different types of ships. Results Noise characteristics of ships appear to differ significantly based on size, categorized into three groups, namely under 30 GT (Fig. 3 ), between 30 and 100 GT (Fig. 4 ), and exceeding 100 GT (Fig. 5 ). Small-sized vessels, typically traditional fishing boats under 30 GT (Fig. 3 A), generate sound pressure levels (SPL) ranging from 6 to 56 Pa (Fig. 3 B), which corresponds to approximately 122 to 144 dB re 1 µPa (Fig. 3 C). This variation in SPL can be attributed to differences in operational speed, even when the size and type of engine are relatively similar (equipped with 20 HP gasoline-fueled outboard engine). Specifically, noise produced by faster-moving ship traveling at 3.1 m s − 1 (Fig. 3 A, left) is noticeably greater than that emitted by their slower counterparts, which operate at speeds of only 2.6 and 2.3 m s − 1 (Fig. 3 A, right and center). The SPL tends to decrease more rapidly with distance for ships traveling at higher speeds, suggesting that the duration of exposure to noise pollution is shorter at any given point in the water. This suggests that sound emitted by faster ships dissipates more quickly. Another notable characteristic related to the speed is the difference in duration intervals, where slower-moving types generate longer sound duration. This relationship shows how operational speed not only influences the intensity of noise but also affects the temporal patterns of sound emission in marine environments. Similar to SPL, ships under 30 GT also emit a range of frequencies (Fig. 3 D). Although the frequencies produced are considered broadband, both the dominant frequency and range can differ significantly from one ship to another. Generally, smaller ships show a dominant frequency of around 10 kHz, with the highest value reaching up to 25 kHz. At higher speeds (Fig. 3 D, left) there is a tendency to generate a narrower frequency bandwidth compared to slower counterparts (Fig. 3 D, right and center). The frequencies produced by faster ships can be higher than those emitted by slower ones. This variation in sound exposure time in the water, resulting from different operational speeds, is shown by the SPL and spectrum graph. Additionally, the duration of sound intervals plays a crucial role, as ships operating at lower speeds show longer duration intervals (Fig. 3 D). This relationship underscores the intricate dynamics of how speed influences both the frequency characteristics and the temporal patterns of sound emissions in marine environments, further showing the potential impacts on aquatic ecosystems. Figure 4 illustrates the various types of medium-sized (30–100 GT) and their operational speeds, showing the characteristics of noise generated in terms of SPL and frequency. This category primarily consists of fishing ships equipped with different types of gear operating in the study location. The larger ship shown on the right side of Fig. 4 A possesses a more powerful engine compared to its smaller counterparts shown on both the left and right. Despite larger engine capacities, large ships tend to operate at lower speeds than smaller ones. This disparity in size and operational speed contributes to variations in noise emissions, leading to varying acoustic profiles. Understanding these kinds of variations is important for the checking of how noise is affecting marine environments. The differences in noise characteristics among the three ships are shown in SPL and frequency produced, as presented in Figs. 4 B-D. The larger ship (60 GT) generates significantly lower sound intensity compared to the other vessels (45 GT). This low intensity is not attributed to size or engine power but primarily influenced by slower operational speed. Specifically, the larger ships (equipped with 150 HP diesel-fueled inboard engines) produce SPL below 4 Pa, which is approximately equivalent to 100 dB re 1 µPa (Figs. 4 B and C, right). Due to its low speed (0.9 m s-1), the reduction in intensity over distance (which reflects travel time) occurs at a slower rate. In comparison, the two smaller ships emit a much higher SPL, exceeding 80 Pa, or around 96 dB re 1 µPa, as shown in Figs. 4 B and C (center and left). Although these two ships are similar in size and engine type (equipped with 120 HP diesel-fueled inboard engines), their noise intensity and the patterns of intensity change with distance difference. The ships with higher operational speed (2.1 m s − 1 compared to 1.8 m s − 1 ) produce a greater SPL, but this is not accompanied by a faster decrease in intensity over distance. This phenomenon indicates that higher sound intensity can be perceived at greater distances, showing the complex relationship between size, speed, and sound emissions. The variation in noise produced by differences in size and operational speed is clearly reflected in the spectral characteristics, as shown in Fig. 4 D. The larger ships not only show lower sound intensity and frequencies compared to their smaller counterparts. Although the dominant frequency can reach approximately 9 kHz, the maximum frequency remains below 22 kHz, which is considerably lower than the smaller ships producing frequencies of 30 kHz. Additionally, the operational speed of each ship influences the peak frequency observed. Faster-moving ships tend to produce a broader frequency range, leading to a more extensive acoustic profile. The differences in operational speed also led to variations in the duration of sound pulses, as shown by the spectrogram in Fig. 4 D. Understanding these spectral differences is crucial for analyzing the acoustic impact of different ships on the surrounding marine environment, which can affect marine life and habitat dynamics significantly. The variations in noise characteristics, influenced by size and operational speed, become increasingly apparent among larger ships (over 100 GT), as shown in Fig. 5 . These ships serve various commercial purposes, which contribute to differences in their dimensions, engine types, and operational speeds. For instance, ferryboat (Fig. 5 A, right) is designed to transport passengers between distant islands and is equipped with powerful engines (900 HP gasoline-fueled inboard engine) that enable higher operational speeds. In comparison, tugboat (Fig. 5 A, center) play a crucial role in maritime operations, assisting larger ships with maneuvering (such as docking, undocking, or navigating narrow waterways), towing disabled ships, and providing emergency support for situations like firefighting and oil spill management. Due to their significant responsibilities, tugboats are outfitted with large engine capacity (1,500 HP diesel-fueled inboard engine), but operate at slower speeds. Patrol boat (Fig. 5 A, left) are tasked with maintaining maritime security, preventing crimes like smuggling and robbery, and enforcing maritime laws. These ships also feature powerful engines (600 HP gasoline-fueled outboard engine) and high operational speeds. Despite both types being equipped with high-capacity engines, the differences in their engine types lead to distinct noise characteristics. The noise characteristics based on SPL for the three types of large ships are shown in Figs. 5 B and C. Both ferry boat and tugboat show higher sound intensity due to greater engine capacities compared to patrol boats. Although both boats can achieve SPL of approximately 155 dB re 1 µPa, tugboat experience a more rapid decrease in intensity. This is attributed to their use of inboard diesel engines, which typically produce different acoustic profiles than the inboard gasoline engines found in ferry boat. In comparison, patrol boat, which are also equipped with inboard gasoline engines of lower power, generate noise at a lower intensity range of 110 to 140 dB re 1 µPa. This engine type, combined with the patrol boats' relatively high operational speeds, results in quicker changes in sound intensity over distance. Similar to smaller ships under 30 GT and between 30–100 GT, noise characteristics of larger ships (exceeding 100 GT) are shown by sound intensity produced and spectral properties (Fig. 5 D). For example, ferry boats show a narrower broadband in spectral characteristics but with a dominant frequency reaching 25 kHz. This is a significant comparison to both tugboat and patrol boats which typically emit a dominant frequency of only 9 kHz and have a peak frequency reaching 22 kHz. The differences in these spectral characteristics are influenced by engine capacity and operational speeds. This is because faster ships tend to produce higher frequencies, while those operating at slower speeds might generate lower frequencies. The relationship between these factors underscores the complexity of sound production, providing valuable insights into how different ships interact with their acoustic environments. Discussion Size plays a crucial role in determining the characteristics of underwater noise, significantly influencing the acoustic environment in marine ecosystems. Each ship’s functional variations lead to notable differences in several key aspects, including size, type, engine power, payload capacity, and operational speed. The relationship between noise features and various components including engine type, propulsion system, and propeller design, is particularly important (Ebrahimi et al., 2019 ; Saettone et al., 2020 ). Generally, sound is generated from multiple sources, including the propeller, main engines, auxiliary engines, and flow noise produced by the interaction of water with the ship's hull (Pazara et al., 2018 ). The mechanisms included in the sound production system are influenced by physical characteristics and engine type (McKenna et al., 2012 ). This relationship shows the complexity of underwater acoustics, as different engines and designs yield varying sound profiles that can have significant implications for marine life. For instance, smaller ships, often equipped with high-speed engines, tend to produce higher-frequency sounds (Brooker & Humphrey, 2016 ). In comparison, larger ships typically generate lower-frequency noise (McKenna et al., 2012 ). The noise level of ships increases during operation due to the combined impacts of engine operation, propeller propulsion, and hydrodynamic interactions (Cianferra et al., 2019 ; Taskar et al., 2016 ). Small ships (< 30 GT), consisting of traditional fishing boats, produce noise with varying intensity and frequency that is significantly influenced by their operating speed. Although many of these ships have similar engine types and sizes, those operating at higher speed generate greater sound pressures. The increased noise is accompanied by more rapid decline in SPL as the distance from the source increases. Previous studies have shown power and type of engine on small fishing ships have a more significant impact on underwater noise levels. The highest speeds typically yield the greatest noise levels but within a very limited frequency range. Additionally, ships with similar speeds and different engines show shifts in their acoustic spectra (Picciulin et al., 2022 ). A major contributor to noise produced by small fishing ships is the propeller. In certain operational modes, engine can generate noise with high intensity, which significantly adds to the overall sound produced. Helal et al., ( 2024 ) stated that propeller was important in creating detectable sounds in the underwater environment. The noise intensity from this type of ships can be identified at specific distances, showing a decay pattern where higher frequencies decrease more rapidly with increasing distance (Amron, et al., 2021 a; Amron, et al., 2021 b). Medium-sized ships (30–100 GT), which are predominantly used for fishing activities, show a notable variation in noise levels that require further examination. These ships are generally larger in size and equipped with more powerful engines, operating at lower speeds compared to their smaller counterparts. Consequently, there is production of lower SPL and frequencies that can reach higher speeds. The observation shows the importance of speed as a factor influencing both the intensity and frequency of sound, often outweighing the capacity of the engine (McKenna et al., 2013 ). The propulsion engine, along with auxiliary equipment, plays a significant role in determining the overall noise output of ships. These components are identified as the primary sources of noise, as their operation is intrinsically related to the movement of ships (Burella et al., 2019 ). When the engine runs, it not only propels the ship but also generates vibrations and sound waves that contribute to the underwater acoustic environment. Large ships (over 100 GT), including ferry, patrol, and tugboats, make different noise because of variations in engine and function. Although ferry and patrol boats are equipped with high-powered gasoline engines, there are special noise profiles due to variations in operating speed. In comparison, tugboats, which use inboard diesel engines, generate higher sound levels but experience more rapid sound attenuation. This suggests that engine type, which influences speed plays a major role in determining the characteristics of sound propagation in marine environments (McKenna et al., 2013 ; Parsons et al., 2021 ). Differences in ship, hull designs, construction materials, and propulsion systems significantly impact the noise characteristics (Fischer & Boroditsky, 2024 ). Generally, larger ships produce lower frequency sounds due to increased size, reduced engine revolutions per minute (RPM), and specific propeller designs (McKenna et al., 2012 ). As these ships operate, the likelihood of cavitation noise tends to rise with higher speed, size, and load (Amron, et al., 2021 b; Hamson, 1997 ; Scrimger & Heitmeyer, 1991 ; Trevorrow et al., 2008 ). The variations in noise characteristics related to size and speed show acoustic impacts that vary both spatially and temporally, suggesting the potential for significant ecological disturbances. Previous studies have shown that anthropogenic noise generated by ships based on broadband frequencies of varying intensities negatively affects marine life. The consequences for marine mammals and fish can manifest as stress (Kight & Swaddle, 2011 ; Rolland et al., 2012 ; Wright et al., 2011 ), causing changes in behavior (Halliday et al., 2017 ), physiological alterations (Codarin et al., 2009 ; Erbe et al., 2016 ), and other health impacts (Casper et al., 2013 ; Di Franco et al., 2020 ; Tougaard et al., 2015 ), including damage to the auditory system (Halliday et al., 2017 ; Slabbekoorn et al., 2010 ). Based on these results, there is a need for coastal management and shipping regulations to integrate considerations of speed, navigation routes, and advanced noise reduction technologies, such as quieter propeller designs and acoustic insulation for engines. A thorough understanding of how ship type (including engine size and power) interacts with speed to influence noise characteristics is essential for effectively studying underwater noise pollution, particularly in regions like Indonesia. This understanding serves as a foundational element in developing policies to mitigate acoustic impacts, thereby helping to preserve the balance of marine ecosystems. Conclusion In conclusion, this study showed that noise characteristics of ships in the Java Sea were significantly affected by size, engine type, and operational speed. Smaller ships ( 100 GT) showed variations in SPL and frequency spectrum influenced by speed, engine type, and capacity. High-speed ships tend to produce greater intensity and frequency with shorter sound exposure durations, while those with slower operational speed had longer sound durations and low frequencies. These variations were crucial for understanding underwater noise pollution, as each type of ship creates a distinct acoustic footprint in the marine environment. Furthermore, the results showed the importance of careful management of shipping activities to reduce noise impact on Indonesia's marine ecosystems. Declarations Author Contribution Conceptualization, AA, RRH, IAH, DS and HH; methodology, AA, RRH, ATN, and RJS; validation, AA, RRH and IAH; formal analysis, AA, HRR, DS, and HH; investigation, AA, RRH, IAH, DS and HH; resources, AA, RRH, IAH, DS, ATN, RJS, and HH; data curation, AA, IAH, DS and HH; writing original draft preparation, AA, RRH, IAH, DS, ATN, RJS, and HH; writing review and editing, AA and HRR; supervision, AA, DS and HH; project administration, RJS; funding acquisition, AA, RRH, IAH, DS and HH. All authors have read and agreed to the published version of the manuscript. References Amron, A., Hidayat, R. R., Meinita, M. D. N., & Trenggono, M. (2021). 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The Journal of the Acoustical Society of America , 89 (2), 691–699. https://doi.org/10.1121/1.1894628 Slabbekoorn, H., Bouton, N., van Opzeeland, I., Coers, A., ten Cate, C., & Popper, A. N. (2010). A noisy spring: the impact of globally rising underwater sound levels on fish. Trends in Ecology & Evolution , 25 (7), 419–427. https://doi.org/10.1016/j.tree.2010.04.005 Soares, C., Pacheco, A., Zabel, F., González-Goberña, E., & Sequeira, C. (2020). Baseline assessment of underwater noise in the Ria Formosa. Marine Pollution Bulletin , 150 , 110731. https://doi.org/10.1016/j.marpolbul.2019.110731 Taskar, B., Yum, K. K., Steen, S., & Pedersen, E. (2016). The effect of waves on engine-propeller dynamics and propulsion performance of ships. Ocean Engineering , 122 , 262–277. https://doi.org/10.1016/j.oceaneng.2016.06.034 Tougaard, J., Wright, A. J., & Madsen, P. T. (2015). Cetacean noise criteria revisited in the light of proposed exposure limits for harbour porpoises. Marine Pollution Bulletin , 90 (1–2), 196–208. https://doi.org/10.1016/j.marpolbul.2014.10.051 Trevorrow, M. V, Vasiliev, B., & Vagle, S. (2008). Directionality and maneuvering effects on a surface ship underwater acoustic signature. The Journal of the Acoustical Society of America , 124 (2), 767–778. https://doi.org/10.1121/1.2939128 Wright, A. J., Deak, T., & Parsons, E. C. M. (2011). Size matters: management of stress responses and chronic stress in beaked whales and other marine mammals may require larger exclusion zones. Marine Pollution Bulletin , 63 (1–4), 5–9. https://doi.org/10.1016/j.marpolbul.2009.11.024 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-6624854","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":456222726,"identity":"2ef6f730-8d3d-4d94-93c4-c50e7f4e9af3","order_by":0,"name":"Amron Amron","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAx0lEQVRIiWNgGAWjYNCCCgglASLYGBKI0XKGZC2MbUhaGAhp4Z929uHjwnmH8+Tbmw/eYKixY+BjJ6BF4na6sfHMbYeLDc4cS7ZgOJbMwMbzgICjbqexSfNuO5y4QSLHTIKB7QADmwQBW+TBWuYcTpw/I/+bBMM/IrQYgLU0HE5suJHDJsHYRoQWw9tpzMY8x9ITN5w5ZmyR2JfMQ9AvcrfTGB/z1Fgnzm9vfnjjwzc7Ofl2AragAqBiHlLUj4JRMApGwSjAAQCyND1XCKrSgAAAAABJRU5ErkJggg==","orcid":"","institution":"Jenderal Soedirman University","correspondingAuthor":true,"prefix":"","firstName":"Amron","middleName":"","lastName":"Amron","suffix":""},{"id":456222727,"identity":"1554af88-7b2c-427f-b712-e49f6ebbce3a","order_by":1,"name":"Rizqi Rizaldi Hidayat","email":"","orcid":"","institution":"Jenderal Soedirman University","correspondingAuthor":false,"prefix":"","firstName":"Rizqi","middleName":"Rizaldi","lastName":"Hidayat","suffix":""},{"id":456222728,"identity":"1a8e486b-aeef-44f6-9fd8-2dd3831b621e","order_by":2,"name":"Iqbal Ali Husni","email":"","orcid":"","institution":"Jenderal Soedirman University","correspondingAuthor":false,"prefix":"","firstName":"Iqbal","middleName":"Ali","lastName":"Husni","suffix":""},{"id":456222729,"identity":"1ad6746a-71eb-4651-b0f1-d72f682db100","order_by":3,"name":"Dyahruri Sanjayasari","email":"","orcid":"","institution":"Jenderal Soedirman University","correspondingAuthor":false,"prefix":"","firstName":"Dyahruri","middleName":"","lastName":"Sanjayasari","suffix":""},{"id":456222730,"identity":"5772d13c-ecba-45a4-9e9c-23c534ed3ccf","order_by":4,"name":"Agung Tri Nugroho","email":"","orcid":"","institution":"Jenderal Soedirman University","correspondingAuthor":false,"prefix":"","firstName":"Agung","middleName":"Tri","lastName":"Nugroho","suffix":""},{"id":456222731,"identity":"146dc6e2-dee2-42b9-a0dd-4ac1b185b777","order_by":5,"name":"Ratna Juita Sari","email":"","orcid":"","institution":"Jenderal Soedirman University","correspondingAuthor":false,"prefix":"","firstName":"Ratna","middleName":"Juita","lastName":"Sari","suffix":""},{"id":456222732,"identity":"94f99ce1-847f-4bbd-ba11-301995ab70fb","order_by":6,"name":"Hartoyo Hartoyo","email":"","orcid":"","institution":"Jenderal Soedirman University","correspondingAuthor":false,"prefix":"","firstName":"Hartoyo","middleName":"","lastName":"Hartoyo","suffix":""}],"badges":[],"createdAt":"2025-05-09 04:08:23","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6624854/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6624854/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":82874798,"identity":"d19b5f31-18ca-475d-b18f-48d59ea59b27","added_by":"auto","created_at":"2025-05-16 09:31:02","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":76353,"visible":true,"origin":"","legend":"\u003cp\u003eResearch stations\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6624854/v1/7221383f077b87bcab0ebf33.jpg"},{"id":82874799,"identity":"5b6ea8cc-3f95-4691-8db7-ed8175880277","added_by":"auto","created_at":"2025-05-16 09:31:02","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":47986,"visible":true,"origin":"","legend":"\u003cp\u003eDesign of data acquisition\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6624854/v1/494521673d8e47d44fbbe233.jpg"},{"id":82874801,"identity":"e46eeaa3-ab3e-4680-b1f0-98177bc1857b","added_by":"auto","created_at":"2025-05-16 09:31:02","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":212223,"visible":true,"origin":"","legend":"\u003cp\u003eNoise emissions from small-sized vessels (\u0026lt;30 GT) with varying operational speed. (A) type vessel; (B) SPL in Pa; (C) SPL in dB re 1 µPa; and (D) Frequency in kHz\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6624854/v1/40df3600f874f450b5054eba.jpg"},{"id":82874800,"identity":"4f405cbf-078b-426d-9aa4-d690e91a32ba","added_by":"auto","created_at":"2025-05-16 09:31:02","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1672646,"visible":true,"origin":"","legend":"\u003cp\u003eNoise emissions from medium-sized vessels (30-100 GT) with varying operational speed. (A) type vessel; (B) SPL in Pa; (C) SPL in dB re 1 µPa; and (D) Frequency in kHz\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6624854/v1/bc0735f138c498ad0d361b7a.jpg"},{"id":82876339,"identity":"30c2a7f7-c5f8-4854-8ad7-5821868185bd","added_by":"auto","created_at":"2025-05-16 09:47:03","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1916961,"visible":true,"origin":"","legend":"\u003cp\u003eNoise emissions from large-sized vessels (\u0026gt;100 GT) with varying operational speed. (A) type vessel; (B) SPL in Pa; (C) SPL in dB re 1 µPa; and (D) Frequency in kHz\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-6624854/v1/eb120a4e1873c7cb1d597753.jpg"},{"id":103288692,"identity":"b13598aa-17bc-4173-97b2-e59b12a8e728","added_by":"auto","created_at":"2026-02-24 05:40:30","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4355998,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6624854/v1/16f4c529-9323-47a8-8cca-c69fbb6d4b98.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Ship Noise Characteristics in the Java Sea: A Preliminary Study on Underwater Noise Pollution in Indonesia","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAs the largest archipelagic nation in the world, Indonesia has significant potential for marine resources that is unparalleled. This nation has over 17,000 islands, showing substantial opportunities across multiple sectors, including fisheries, mining, shipping, tourism, defense, and the maritime industry. Particularly, fisheries resources serve as a fundamental pillar of the national economy that supports the livelihoods of many individuals for income and sustenance. Despite the significant potential, Indonesia faces environmental challenges that must be addressed, particularly related to the detrimental impacts of noise generated by various economic activities underwater. This noise pollution is recognized worldwide as a threat to aquatic ecosystems and the long-term sustainability of the resources (Gullett, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eShipping activities, which include several operations such as fishing, cargo transportation, and marine tourism, are primary sources of noise pollution in water of Indonesia. Previous studies have shown that several factors contribute to the variations in sound characteristics produced by ships, such as size, the materials used in construction, engine power, and operational speeds (McKenna et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Santos-Dom\u0026iacute;nguez et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; Soares et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). The noise generated by these ships disrupts the comfort of individuals at sea, posing significant negative impacts on marine biota, which plays a crucial role in maintaining the health of aquatic ecosystems. For example, low-frequency sound emitted by ships can propagate over long distances beneath the water surface, potentially interfering with the communication patterns and behaviors of various marine species (Amron, et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2021\u003c/span\u003ea).\u003c/p\u003e \u003cp\u003eThe impacts of anthropogenic noise on marine biota have increasingly become the subject of extensive studies within the scientific community. Several studies have shown that the noise produced by ships can induce stress responses in marine mammals and fish, leading to significant alterations in their behaviors related to foraging, social interactions, and reproductive activities (Kight \u0026amp; Swaddle, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Rolland et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Wright et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). In addition to the behavioral changes, the physiological repercussions of noise can disrupt essential bodily functions, causing modifications to feeding patterns, growth rates, and reproductive success, which contribute to a decline in the populations of certain species (Halliday et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Nabe-Nielsen et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). This underscores the critical importance of understanding and effectively managing the impacts of noise generated by shipping activities essential for preserving marine ecosystems.\u003c/p\u003e \u003cp\u003eDespite numerous studies, there is still limited information on the impact of noise generated by ships operating in Indonesian waters. For better understanding, extensive investigation is required to examine the characteristics of noise emitted by various types of ships in terms of frequency and intensity. The sound produced by ships is not always the same and changes due to many reasons such as size, engine power, and speed of movement. Smaller ships with engines that go faster usually make sound with higher frequency, while larger ones make lower type of frequency (Brooker \u0026amp; Humphrey, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2016\u003c/span\u003e; McKenna et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Extra noise can also come because of engine operation, the spinning propeller, and the moving of ships in water which is called hydrodynamic impact (Ghaemi \u0026amp; Zeraatgar, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Taskar et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). When noise occurs for a long period, serious impacts can happen to biota in the water. This is because different species in water do not have the same ability to handle sound. Some species have the ability to adjust a little, but others are showing strong problems with noise (Popper \u0026amp; Hawkins, 2016; Soares et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Therefore, more investigations must be performed on how different ships create sound and its impact, especially in Indonesia. This kind of understanding is needed because water sound situation depends on type of ship.\u003c/p\u003e \u003cp\u003eBased on the background above, this study aimed to examine the noise characteristics, including frequency and intensity of ships operating in the Java Sea, Indonesia. By exploring these dimensions, the results are expected to enhance the understanding of the impacts of noise on aquatic ecosystems and marine biota. Furthermore, the results are anticipated to serve as a reference for developing more effective policies regarding the management of fisheries resources and the protection of Indonesia's aquatic environment. When insight is gained, strategies can be identified to mitigate the adverse impacts of noise on marine life. The information is particularly crucial, as the sustainability of fisheries resources and the overall health of aquatic ecosystems rely on maintaining a balance between human activities and the survival of marine species. Therefore, this study holds significance for advancing scientific knowledge and informing policy-making that promotes the sustainability of fisheries resources in Indonesia.\u003c/p\u003e"},{"header":"Material and Methods","content":"\u003cp\u003eNoise generated by various types of ships with different tonnages was recorded in the Java Sea using a calibrated omnidirectional hydrophone (Sea Phone SQ26-08). The research was conducted in specific locations around Jepara (30\u0026ndash;100 GT and over 100 GT), Semarang (under 30 GT and over 100 GT), Pekalongan (under 30 GT), and Tegal (under 30 GT and 30\u0026ndash;100 GT) during August 2023 and April 2025 (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The study sites were characterized by shallow depth and muddy seabed. To capture the acoustic data, hydrophone was strategically deployed on study ship, positioned approximately 1.5 meters below the sea surface, effectively functioning as a surface-based system. This hydrophone boasts a sensitivity of -194 dB re 1 V.\u0026micro;Pa⁻\u0026sup1;, a flat response ranges from 20 Hz to 45 kHz, and a gain of 25 dB. It was connected to a sound recorder capable of 16-bit recordings at a sampling rate of 44,100 Hz, with all audio files saved in WAV format. In comparison, ships navigating through the study location was documented using a high-definition CCTV camera with a resolution of 1080 MP. Sound and video recordings were synchronized and connected to a Zoom H1n digital recorder, allowing for real-time monitoring and observation on an LCD display. Information regarding engine size and type was obtained from the ship owner and crew, while the ship's operational speed was recorded using a vehicle speed radar detector. This full setup was not only for catching the noise from the ships but also was giving pictures, enhancing the analysis of the acoustic environment. The integration of advanced recording technologies and strategic positioning facilitated a thorough investigation into the impact of maritime activities on underwater soundscapes.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe sound recording file in *.wav is initially opened in Audacity for processing before analysis in MATLAB. For data preparation, noise removal is applied with a high-pass filter where the cutoff frequency is set at 1 kHz. After step this, waveform analysis is performed to extract key parameters such as intensity, frequency, pulse duration, and interval duration. Waveform analysis is then conducted to determine parameters such as intensity, frequency, pulse duration, and interval duration. Sounds \u003cem\u003eS\u003c/em\u003e(\u003cem\u003et\u003c/em\u003e) were recorded in volts and then converted to sound pressure, \u003cem\u003eP\u003c/em\u003e(\u003cem\u003et\u003c/em\u003e) in \u0026micro;Pa based on the time-domain (\u003cem\u003et\u003c/em\u003e). This was conducted using the following equation:\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:P\\left(t\\right)=S\\left(t\\right)\\times\\:{10}^{\\frac{-G}{20}}\\times\\:D\\times\\:{10}^{\\frac{-SH}{20}}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e \u003cem\u003eRL\u003c/em\u003e (\u003cem\u003et\u003c/em\u003e) in dB re 1 \u0026micro;Pa \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:=20\\text{log}P\\left(t\\right)\\)\u003c/span\u003e\u003c/span\u003e, where \u003cem\u003eG\u003c/em\u003e (in dB) represents the recorder gain (set at 25 dB), \u003cem\u003eD\u003c/em\u003e is a constant reflecting the dynamic response of the recorder (1.4 V for this specific model), and \u003cem\u003eSH\u003c/em\u003e denotes the sensitivity of the hydrophone. Additionally, the type of ships responsible for generating the noise is analyzed using video recordings, providing further context to the acoustic data collected. This combined approach allows for a comprehensive understanding of the acoustic environment influenced by different types of ships.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eNoise characteristics of ships appear to differ significantly based on size, categorized into three groups, namely under 30 GT (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), between 30 and 100 GT (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e), and exceeding 100 GT (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e). Small-sized vessels, typically traditional fishing boats under 30 GT (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA), generate sound pressure levels (SPL) ranging from 6 to 56 Pa (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eB), which corresponds to approximately 122 to 144 dB re 1 \u0026micro;Pa (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eC). This variation in SPL can be attributed to differences in operational speed, even when the size and type of engine are relatively similar (equipped with 20 HP gasoline-fueled outboard engine). Specifically, noise produced by faster-moving ship traveling at 3.1 m s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA, left) is noticeably greater than that emitted by their slower counterparts, which operate at speeds of only 2.6 and 2.3 m s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA, right and center). The SPL tends to decrease more rapidly with distance for ships traveling at higher speeds, suggesting that the duration of exposure to noise pollution is shorter at any given point in the water. This suggests that sound emitted by faster ships dissipates more quickly. Another notable characteristic related to the speed is the difference in duration intervals, where slower-moving types generate longer sound duration. This relationship shows how operational speed not only influences the intensity of noise but also affects the temporal patterns of sound emission in marine environments.\u003c/p\u003e \u003cp\u003eSimilar to SPL, ships under 30 GT also emit a range of frequencies (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eD). Although the frequencies produced are considered broadband, both the dominant frequency and range can differ significantly from one ship to another. Generally, smaller ships show a dominant frequency of around 10 kHz, with the highest value reaching up to 25 kHz. At higher speeds (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eD, left) there is a tendency to generate a narrower frequency bandwidth compared to slower counterparts (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eD, right and center). The frequencies produced by faster ships can be higher than those emitted by slower ones. This variation in sound exposure time in the water, resulting from different operational speeds, is shown by the SPL and spectrum graph. Additionally, the duration of sound intervals plays a crucial role, as ships operating at lower speeds show longer duration intervals (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eD). This relationship underscores the intricate dynamics of how speed influences both the frequency characteristics and the temporal patterns of sound emissions in marine environments, further showing the potential impacts on aquatic ecosystems.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e illustrates the various types of medium-sized (30\u0026ndash;100 GT) and their operational speeds, showing the characteristics of noise generated in terms of SPL and frequency. This category primarily consists of fishing ships equipped with different types of gear operating in the study location. The larger ship shown on the right side of Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA possesses a more powerful engine compared to its smaller counterparts shown on both the left and right. Despite larger engine capacities, large ships tend to operate at lower speeds than smaller ones. This disparity in size and operational speed contributes to variations in noise emissions, leading to varying acoustic profiles. Understanding these kinds of variations is important for the checking of how noise is affecting marine environments.\u003c/p\u003e \u003cp\u003eThe differences in noise characteristics among the three ships are shown in SPL and frequency produced, as presented in Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB-D. The larger ship (60 GT) generates significantly lower sound intensity compared to the other vessels (45 GT). This low intensity is not attributed to size or engine power but primarily influenced by slower operational speed. Specifically, the larger ships (equipped with 150 HP diesel-fueled inboard engines) produce SPL below 4 Pa, which is approximately equivalent to 100 dB re 1 \u0026micro;Pa (Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB and C, right). Due to its low speed (0.9 m s-1), the reduction in intensity over distance (which reflects travel time) occurs at a slower rate. In comparison, the two smaller ships emit a much higher SPL, exceeding 80 Pa, or around 96 dB re 1 \u0026micro;Pa, as shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB and C (center and left). Although these two ships are similar in size and engine type (equipped with 120 HP diesel-fueled inboard engines), their noise intensity and the patterns of intensity change with distance difference. The ships with higher operational speed (2.1 m s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e compared to 1.8 m s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) produce a greater SPL, but this is not accompanied by a faster decrease in intensity over distance. This phenomenon indicates that higher sound intensity can be perceived at greater distances, showing the complex relationship between size, speed, and sound emissions.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe variation in noise produced by differences in size and operational speed is clearly reflected in the spectral characteristics, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eD. The larger ships not only show lower sound intensity and frequencies compared to their smaller counterparts. Although the dominant frequency can reach approximately 9 kHz, the maximum frequency remains below 22 kHz, which is considerably lower than the smaller ships producing frequencies of 30 kHz. Additionally, the operational speed of each ship influences the peak frequency observed. Faster-moving ships tend to produce a broader frequency range, leading to a more extensive acoustic profile. The differences in operational speed also led to variations in the duration of sound pulses, as shown by the spectrogram in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eD. Understanding these spectral differences is crucial for analyzing the acoustic impact of different ships on the surrounding marine environment, which can affect marine life and habitat dynamics significantly.\u003c/p\u003e \u003cp\u003eThe variations in noise characteristics, influenced by size and operational speed, become increasingly apparent among larger ships (over 100 GT), as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e. These ships serve various commercial purposes, which contribute to differences in their dimensions, engine types, and operational speeds. For instance, ferryboat (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eA, right) is designed to transport passengers between distant islands and is equipped with powerful engines (900 HP gasoline-fueled inboard engine) that enable higher operational speeds. In comparison, tugboat (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eA, center) play a crucial role in maritime operations, assisting larger ships with maneuvering (such as docking, undocking, or navigating narrow waterways), towing disabled ships, and providing emergency support for situations like firefighting and oil spill management. Due to their significant responsibilities, tugboats are outfitted with large engine capacity (1,500 HP diesel-fueled inboard engine), but operate at slower speeds. Patrol boat (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eA, left) are tasked with maintaining maritime security, preventing crimes like smuggling and robbery, and enforcing maritime laws. These ships also feature powerful engines (600 HP gasoline-fueled outboard engine) and high operational speeds. Despite both types being equipped with high-capacity engines, the differences in their engine types lead to distinct noise characteristics.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe noise characteristics based on SPL for the three types of large ships are shown in Figs.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eB and C. Both ferry boat and tugboat show higher sound intensity due to greater engine capacities compared to patrol boats. Although both boats can achieve SPL of approximately 155 dB re 1 \u0026micro;Pa, tugboat experience a more rapid decrease in intensity. This is attributed to their use of inboard diesel engines, which typically produce different acoustic profiles than the inboard gasoline engines found in ferry boat. In comparison, patrol boat, which are also equipped with inboard gasoline engines of lower power, generate noise at a lower intensity range of 110 to 140 dB re 1 \u0026micro;Pa. This engine type, combined with the patrol boats' relatively high operational speeds, results in quicker changes in sound intensity over distance.\u003c/p\u003e \u003cp\u003eSimilar to smaller ships under 30 GT and between 30\u0026ndash;100 GT, noise characteristics of larger ships (exceeding 100 GT) are shown by sound intensity produced and spectral properties (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eD). For example, ferry boats show a narrower broadband in spectral characteristics but with a dominant frequency reaching 25 kHz. This is a significant comparison to both tugboat and patrol boats which typically emit a dominant frequency of only 9 kHz and have a peak frequency reaching 22 kHz. The differences in these spectral characteristics are influenced by engine capacity and operational speeds. This is because faster ships tend to produce higher frequencies, while those operating at slower speeds might generate lower frequencies. The relationship between these factors underscores the complexity of sound production, providing valuable insights into how different ships interact with their acoustic environments.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eSize plays a crucial role in determining the characteristics of underwater noise, significantly influencing the acoustic environment in marine ecosystems. Each ship\u0026rsquo;s functional variations lead to notable differences in several key aspects, including size, type, engine power, payload capacity, and operational speed. The relationship between noise features and various components including engine type, propulsion system, and propeller design, is particularly important (Ebrahimi et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Saettone et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Generally, sound is generated from multiple sources, including the propeller, main engines, auxiliary engines, and flow noise produced by the interaction of water with the ship's hull (Pazara et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). The mechanisms included in the sound production system are influenced by physical characteristics and engine type (McKenna et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). This relationship shows the complexity of underwater acoustics, as different engines and designs yield varying sound profiles that can have significant implications for marine life. For instance, smaller ships, often equipped with high-speed engines, tend to produce higher-frequency sounds (Brooker \u0026amp; Humphrey, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). In comparison, larger ships typically generate lower-frequency noise (McKenna et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). The noise level of ships increases during operation due to the combined impacts of engine operation, propeller propulsion, and hydrodynamic interactions (Cianferra et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Taskar et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2016\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eSmall ships (\u0026lt;\u0026thinsp;30 GT), consisting of traditional fishing boats, produce noise with varying intensity and frequency that is significantly influenced by their operating speed. Although many of these ships have similar engine types and sizes, those operating at higher speed generate greater sound pressures. The increased noise is accompanied by more rapid decline in SPL as the distance from the source increases. Previous studies have shown power and type of engine on small fishing ships have a more significant impact on underwater noise levels. The highest speeds typically yield the greatest noise levels but within a very limited frequency range. Additionally, ships with similar speeds and different engines show shifts in their acoustic spectra (Picciulin et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). A major contributor to noise produced by small fishing ships is the propeller. In certain operational modes, engine can generate noise with high intensity, which significantly adds to the overall sound produced. Helal et al., (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2024\u003c/span\u003e) stated that propeller was important in creating detectable sounds in the underwater environment. The noise intensity from this type of ships can be identified at specific distances, showing a decay pattern where higher frequencies decrease more rapidly with increasing distance (Amron, et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2021\u003c/span\u003ea; Amron, et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2021\u003c/span\u003eb).\u003c/p\u003e \u003cp\u003eMedium-sized ships (30\u0026ndash;100 GT), which are predominantly used for fishing activities, show a notable variation in noise levels that require further examination. These ships are generally larger in size and equipped with more powerful engines, operating at lower speeds compared to their smaller counterparts. Consequently, there is production of lower SPL and frequencies that can reach higher speeds. The observation shows the importance of speed as a factor influencing both the intensity and frequency of sound, often outweighing the capacity of the engine (McKenna et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). The propulsion engine, along with auxiliary equipment, plays a significant role in determining the overall noise output of ships. These components are identified as the primary sources of noise, as their operation is intrinsically related to the movement of ships (Burella et al., \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). When the engine runs, it not only propels the ship but also generates vibrations and sound waves that contribute to the underwater acoustic environment.\u003c/p\u003e \u003cp\u003eLarge ships (over 100 GT), including ferry, patrol, and tugboats, make different noise because of variations in engine and function. Although ferry and patrol boats are equipped with high-powered gasoline engines, there are special noise profiles due to variations in operating speed. In comparison, tugboats, which use inboard diesel engines, generate higher sound levels but experience more rapid sound attenuation. This suggests that engine type, which influences speed plays a major role in determining the characteristics of sound propagation in marine environments (McKenna et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Parsons et al., \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Differences in ship, hull designs, construction materials, and propulsion systems significantly impact the noise characteristics (Fischer \u0026amp; Boroditsky, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Generally, larger ships produce lower frequency sounds due to increased size, reduced engine revolutions per minute (RPM), and specific propeller designs (McKenna et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). As these ships operate, the likelihood of cavitation noise tends to rise with higher speed, size, and load (Amron, et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2021\u003c/span\u003eb; Hamson, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e1997\u003c/span\u003e; Scrimger \u0026amp; Heitmeyer, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e1991\u003c/span\u003e; Trevorrow et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2008\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe variations in noise characteristics related to size and speed show acoustic impacts that vary both spatially and temporally, suggesting the potential for significant ecological disturbances. Previous studies have shown that anthropogenic noise generated by ships based on broadband frequencies of varying intensities negatively affects marine life. The consequences for marine mammals and fish can manifest as stress (Kight \u0026amp; Swaddle, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Rolland et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Wright et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2011\u003c/span\u003e), causing changes in behavior (Halliday et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2017\u003c/span\u003e), physiological alterations (Codarin et al., \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2009\u003c/span\u003e; Erbe et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2016\u003c/span\u003e), and other health impacts (Casper et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Di Franco et al., \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Tougaard et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2015\u003c/span\u003e), including damage to the auditory system (Halliday et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Slabbekoorn et al., \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). Based on these results, there is a need for coastal management and shipping regulations to integrate considerations of speed, navigation routes, and advanced noise reduction technologies, such as quieter propeller designs and acoustic insulation for engines. A thorough understanding of how ship type (including engine size and power) interacts with speed to influence noise characteristics is essential for effectively studying underwater noise pollution, particularly in regions like Indonesia. This understanding serves as a foundational element in developing policies to mitigate acoustic impacts, thereby helping to preserve the balance of marine ecosystems.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn conclusion, this study showed that noise characteristics of ships in the Java Sea were significantly affected by size, engine type, and operational speed. Smaller ships (\u0026lt;\u0026thinsp;30 GT) generated higher dominant frequencies and varying SPL based on speed. In comparison, medium-sized (30\u0026ndash;100 GT) and large ships (\u0026gt;\u0026thinsp;100 GT) showed variations in SPL and frequency spectrum influenced by speed, engine type, and capacity. High-speed ships tend to produce greater intensity and frequency with shorter sound exposure durations, while those with slower operational speed had longer sound durations and low frequencies. These variations were crucial for understanding underwater noise pollution, as each type of ship creates a distinct acoustic footprint in the marine environment. Furthermore, the results showed the importance of careful management of shipping activities to reduce noise impact on Indonesia's marine ecosystems.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eConceptualization, AA, RRH, IAH, DS and HH; methodology, AA, RRH, ATN, and RJS; validation, AA, RRH and IAH; formal analysis, AA, HRR, DS, and HH; investigation, AA, RRH, IAH, DS and HH; resources, AA, RRH, IAH, DS, ATN, RJS, and HH; data curation, AA, IAH, DS and HH; writing original draft preparation, AA, RRH, IAH, DS, ATN, RJS, and HH; writing review and editing, AA and HRR; supervision, AA, DS and HH; project administration, RJS; funding acquisition, AA, RRH, IAH, DS and HH. All authors have read and agreed to the published version of the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAmron, A., Hidayat, R. R., Meinita, M. D. N., \u0026amp; Trenggono, M. (2021). 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J., \u0026amp; Madsen, P. T. (2015). Cetacean noise criteria revisited in the light of proposed exposure limits for harbour porpoises. \u003cem\u003eMarine Pollution Bulletin\u003c/em\u003e, \u003cem\u003e90\u003c/em\u003e(1\u0026ndash;2), 196\u0026ndash;208. https://doi.org/10.1016/j.marpolbul.2014.10.051 \u003c/li\u003e\n\u003cli\u003eTrevorrow, M. V, Vasiliev, B., \u0026amp; Vagle, S. (2008). Directionality and maneuvering effects on a surface ship underwater acoustic signature. \u003cem\u003eThe Journal of the Acoustical Society of America\u003c/em\u003e, \u003cem\u003e124\u003c/em\u003e(2), 767\u0026ndash;778. https://doi.org/10.1121/1.2939128\u003c/li\u003e\n\u003cli\u003eWright, A. J., Deak, T., \u0026amp; Parsons, E. C. M. (2011). Size matters: management of stress responses and chronic stress in beaked whales and other marine mammals may require larger exclusion zones. \u003cem\u003eMarine Pollution Bulletin\u003c/em\u003e, \u003cem\u003e63\u003c/em\u003e(1\u0026ndash;4), 5\u0026ndash;9. https://doi.org/10.1016/j.marpolbul.2009.11.024\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"ship noise, Java Sea, sound pressure level, frequency, sound duration","lastPublishedDoi":"10.21203/rs.3.rs-6624854/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6624854/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIndonesia 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\u0026ndash;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 \u0026micro;Pa 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 \u0026micro;Pa. 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.\u003c/p\u003e","manuscriptTitle":"Ship Noise Characteristics in the Java Sea: A Preliminary Study on Underwater Noise Pollution in Indonesia","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-16 09:30:58","doi":"10.21203/rs.3.rs-6624854/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"c170f9fd-1391-46b4-a6f1-e8489b1cd188","owner":[],"postedDate":"May 16th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-03-26T17:23:18+00:00","versionOfRecord":[],"versionCreatedAt":"2025-05-16 09:30:58","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-6624854","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6624854","identity":"rs-6624854","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}