Ticari gemilerin sualtı gürültülerinin deniz yaşamına etkilerinin azaltılması yöntemleri, MEPC.1/CIRC 906 kılavuzun incelenmesi
Methods of reducing the effects of commercial ships underwater noise on marine life, review of MEPC.1/CIRC 906 guideline
Yazar: HALUK ÇOBAN
Danışman: DR. ÖĞR. ÜYESİ MÜNİR CANSIN ÖZDEN
İstanbul Teknik Üniversitesi / Lisansüstü Eğitim Enstitüsü / Gemi ve Deniz Teknoloji Mühendisliği Ana Bilim Dalı / Gemi ve Deniz Teknolojisi Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2024
Konu: Gemi Mühendisliği = Marine Engineering

Özet:
Sualtı akustiği ile ilgili ilk deney, 1826 yılında İsviçreli fizikçi Jean-Daniel Colladon (1802–1893) ve asistanı Jacques Charles-Francois Sturm (1803–1855) tarafından gerçekleştirilmiştir. Bu deney, sesin suda yayılma hızının havadaki yayılma hızından daha hızlı olduğunu göstermiştir. Deney sırasında iki tekne arasındaki mesafe 10 mil (16 km) olarak belirlenmiş ve iletişim, bir su çanı ile sağlanmıştır. Colladon ve Sturm, deneyde sualtındaki ses dalgalarını gözlemlemek ve bu dalgaların yayılma hızını ölçmek için hem teknik bir yaklaşım hem de yaratıcı bir düşünce yöntemi kullanmıştır. Bu çalışmada, ses dalgalarının su ortamında ne kadar etkili bir şekilde ilerlediği ve havadaki hızlarına oranla çok daha hızlı bir şekilde hareket ettiği kesinleşmiştir. Ayrıca, deneylerden elde edilen ses hızı verileri modern teknolojiyle yapılan ölçümlerle kıyaslandığında oldukça yakın sonuçlar vermiştir. Bu buluş, sualtı akustiği alanındaki bilimsel çalışmaların temelini oluşturarak, gelecekteki pek çok akustik ve deniz bilimi araştırmasına yön vermiştir. Colladon ve Sturm'un bu öncü çabası, hem sualtı iletişim sistemlerinin gelişimine hem de denizcilik alanında yeni teknolojilerin doğmasına katkı sağlamıştır.
20. yüzyılın başlarına gelindiğinde, denizaltıların ve deniz savaşlarının yaygınlaşmasıyla birlikte sualtı akustiğinin önemi büyük ölçüde artmıştır. Bu döneme kadar sualtı akustiği yalnızca basit eko konumlama ve derinlik tespiti ile sınırlı bir alandı. Ancak 20. yüzyılın başlarındaki teknolojik gelişmeler ve özellikle denizaltıların stratejik öneminin artması, bu alandaki çalışmaları hızlandırmıştır. Deniz savaşlarında üstünlük sağlamak isteyen ülkeler, sualtı akustiği teknolojisine büyük yatırımlar yaparak, hem denizaltı tespit hem de iletişim sistemlerini geliştirmiştir. İlk etapta, denizaltıların diğer denizaltılardan ve su araçlarından gelen sesi algılayan pasif sonar sistemleri üzerine yoğunlaşılmıştır. Pasif sonarlar, herhangi bir sinyal yaymadan yalnızca çevredeki sesleri dinleyerek bilgi toplama prensibine dayanmaktadır ve bu sistemler sessiz operasyonların kritik olduğu durumlarda büyük avantaj sağlamıştır. Daha sonraki dönemde, aktif sonar sistemleri geliştirilmiştir. Bu sistemler, ses dalgalarını sualtında yayarak, bu dalgaların hedeflerden geri yansıyan yankılarını tespit etmek amacıyla kullanılmaktaydı. Aktif sonarların geliştirilmesiyle, yalnızca mevcut denizaltıları algılamakla kalınmamış, aynı zamanda sualtı haritalama ve keşif çalışmaları da hız kazanmıştır.
İkinci Dünya Savaşı'nın sona ermesiyle birlikte, bu alanda elde edilen teknolojiler sismik araştırmalarda ve deniz biyolojisinde geniş kullanım alanı bulmuştur. Bu dönemde savaş sırasında geliştirilen sonar ve akustik cihazlar, bilimsel amaçlar için adapte edilmiştir. Sanayileşmenin ve deniz ticaretinin hızla artmasıyla birlikte deniz trafiğindeki yoğunluk önemli ölçüde artmış ve bu durum sualtı gürültü seviyelerinin daha detaylı bir şekilde incelenmesi ihtiyacını doğurmuştur. Artan deniz trafiği, özellikle ticari gemilerden kaynaklanan gürültünün deniz yaşamı üzerindeki etkilerini araştırma gerekliliğini artırmıştır. Bu bağlamda, Uluslararası Denizcilik Örgütü (IMO) bünyesinde faaliyet gösteren ve deniz temizliği ile ekosistemlerin korunması amacıyla kurulan Deniz Kirliliğini Önleme Komitesi (MEPC), bu alanda önemli adımlar atmıştır. Komite, 2014 yılında ticari gemilerden kaynaklanan sualtı gürültüsünün azaltılmasına yönelik bir kılavuz yayınlamıştır. Bu kılavuz, gürültü kaynaklarını ayrı ayrı değerlendirmiş, çözümleme metotlarına yer vermiş ve çözüm yöntemleri için detaylı bir uygulama matrisi eklemiştir. Söz konusu matriste, çözüm teknikleri kaynaklarına göre gruplandırılmış; tersaneler veya armatörlere getireceği finansal yükler detaylı olarak değerlendirilmiş; teknolojik olarak uygulanabilirlik puanlanmış ve çözüm yöntemlerinin hangi frekans aralıklarında etkili olduğu belirtilmiştir. Ayrıca, gürültü azaltım yöntemleri farklı kategorilere ayrılarak, bu yöntemlerin etkinliği ve uygulanabilirliği sınıflandırılmıştır. Bu kılavuz, yalnızca deniz yaşamının korunması için bir rehber niteliği taşımakla kalmamış, aynı zamanda sürdürülebilir denizcilik faaliyetleri için de önemli bir referans olmuştur.
Tez çalışmamda ISO 17208-1 standardına uygun ölçüm metodolojisi incelenmiştir. Bu ölçüm standardındaki ölçümde kullanılacak ekipmanların (hidrofon, veri analizörü, uzaklık ölçüm aletleri) kapasite, ölçüm aralıkları, standart sapmaları, kalibrasyon ve doğrulama periyotları ve ölçüm belirsizlikleri standartta geçen metinler özenle incelenip özetlenmiştir. İlgili standartta tanımlanan test koşulları detaylı bir şekilde açıklanmış, hidrofonun bağlama yöntemleri ve test edilecek geminin yapacağı manevralar incelenmiştir. Ayrıca, bu ölçüm sonrası elde edilen verilerin işlenmesi sürecinde kullanılan arka plan seslerinin ölçüm verilerine dahil edilme formülleri ve verilerin güvenilir sonuçlara dönüştürülmesi için izlenen yöntemler çalışmamın önemli bir parçası olarak sunulmuştur. Gürültü kaynaklarının tanımlanması ve bu kaynaklarla ilgili özet bilgiler detaylı olarak verilmiş, farklı senaryolar için uygulanabilir çözüm yolları incelenmiştir. Bunun yanında, Türk gemi inşa sektörünün güncel durumu ve bu sektörde gelecekte yapılabilecek teknolojik atılımlar ele alınmıştır. Sektöre yönelik olarak geliştirilen çözüm önerileri tezin sonuç bölümünde detaylandırılmıştır.

Abstract:
The first experiment with hydroacoustic participation was performed in 1826 by the Swiss physicist Jean-Daniel Colladon (1802-1893) and his assistant Jacques Charles-Francois Sturm (1803-1855). The goal of this experiment was to measure properties related to the propagation of sound in water and, in particular its significant differences compared with the propagation of sound through the atmosphere. It is in this landmark experiment that the speed of sound in water was found to be much higher, compared to that in air, which was also one shocking discovery given the conception about sound as at then. There were two boats involved, spaced by 10 miles or 16 kilometers, with an underwater bell employed to realize communications between them. That is to say, performing the measurement of the speed of sound waves in realistic and controlled conditions at one time. What Colladon and Sturm's way has expressed is not only a great ingenuity with respect to techniques but, rather even more sensational dose of thinking creative to the solution of scientific problems. The precise measurements obtained in the experiments clearly demonstrated the significantly higher velocity of sound waves in water relative to that in air, providing evidence that sound propagates approximately four times more rapidly in water due to its enhanced density and elasticity. Furthermore, the speed of sound determined through these measurements closely aligns with the values currently validated by contemporary technologies, serving as an affirmation of the accuracy and insightfulness inherent in the methodology employed. This groundbreaking research provided a solid foundation for the new science of underwater acoustics, which later proved to become one of the significant factors in establishing disciplines in the field of marine biology, submarine navigation, and sonar technology. Knowledge accruable from Colladon's and Sturm's works went beyond simple descriptions of acoustic physics by leading the way in improved methodologies in underwater communication. This will catalyze new technology development in the area of underwater research, marine engineering, and even seismic. Their work represents one of the very founding blocks in acoustic science, bearing great testimony to how curiosity and problem-solving innovation are substantial elements when it comes to building up human knowledge.
By the turn of the 20th century, with the proliferation of submarines in addition to the expansion of naval warfare, underwater acoustics was assuming much higher importance. Hitherto, the science of underwater acoustics was limited to simple echo-location and measurement of depth, which were primarily used for navigation and avoidance of obstacles underwater. However, the technological breakthroughs of the early 20th century, combined with the increasing strategic importance of submarines in naval warfare, allowed for rapid development in this field, making it a crucial part of sea defense. Thus, underwater acoustics posed vast possibilities for those countries that wanted to dominate naval warfare, and much money was pumped into research and development to come up with more sophisticated systems of submarine detection and communication.
Preliminary work concerned the passive sonar system-which depends upon the detection of signals emanating from other submarines and underwater craft, without sending signals of their own. This proved vital in instances where the detection itself would prove to be fatal. This capability to know the movement of the enemy without detection by the navies is an unbeatable tactical advantage. Passive sonar has overtime been refined to cover even minute noises underwater propelled by vessels in their propeller sounds for a target with precision to track and classify, complementing their weaknesses further developed active sonar. Active sonar sent out sound waves underwater, analyzing the echoing that came from targets; these greatly helped in more correctly detecting submarines even within noisy or otherwise complicated underwater environs. Its development greatly extends the capability to detect submarines. It has radically changed the ambition of mapping and exploring the sea floor. These systems enabled the detailing of underwater topography in great detail, and submerged object detection became very useful for both military and civilian purposes.
The advantages of underwater acoustics at that moment created the backbone of naval strategy and the systems of underwater defense. It is one of the most epoch-making inventions on high seas, viewed from their comprehensive interference in methods of conducting a naval war and driving along with this, a technological rivalry of some sort among various states; and in light of such facts that these developments were already out of military applications, they made a broader underwater acoustics toward civilian areas of concern. Other than this, the improvements in seismic explorations, undersea archeology, and studies of marine biology owed their debt to the developments underlining very important impacts of underwater acoustic technologies on science and industry.
Following the end of World War II, the technologies developed during this period were now widely applied in seismic research and the study of marine biology, thereby opening new dimensions in scientific exploration. It was during this era that sonar and acoustic devices, originally developed for military purposes, were creatively adapted to satisfy the needs of civilian scientific research. These developments enabled scientists to probe the ocean's interior, mapping the seafloor with a level of detail that had previously been impossible, and studying marine ecosystems in ways that had never been dreamed of. The rapid industrialization and the rise in maritime trade following the war brought into focus the need to understand and manage underwater ecosystems. The steep rise in global shipping activity then resulted in a far higher level of underwater noise pollution, which became an urgent concern for marine ecologists and policymakers alike.
The rapid rise in maritime traffic, especially the incessant noise coming from commercial vessels, highlighted the need for an immediate investigation into its effects on marine ecosystems. This acoustic disturbance, caused mainly by ship engines, propellers, and auxiliary systems, has massive repercussions on marine animals in the disruption of communication, navigation, and behavior of species of aquatic life. The problem was viewed with such concern that the MEPC, under the auspices of the IMO, started to take serious steps to deal with the mounting problem.
In the year 2014, MEPC issued comprehensive guidelines on the reduction of underwater noise from commercial ships as a milestone in international efforts toward environmental improvements in shipping. The model developed gave a holistic approach to the study of the diverse sources of noise, such as engines, propellers, and hull interactions, by providing analytical methods to quantify and assess their effects. One of the salient features of the guidance provided was the unique application matrix dedicated to mitigation measures regarding noise reduction using a grading system of effectiveness for the mitigation strategies looking from the source point of view. The matrix also analyses the financial consequences of this choice of options for shipyards and shipowners, giving a sound method of determining economic feasibility combined with technical ones. Also, the rules defined the ranges of frequency within which a particular technique is considered to be effective at noise reduction and hence determined the frequency above which a noise mitigation approach needs to be adopted. The methods were then categorized into different types, and their uses and efficacies were assessed in detail for the benefit of ship designers, builders, and owners when deciding on their strategies. This guideline has not only created a scientific basis for underwater noise reduction but also placed the reduction of noise in the general context of sustainable maritime.
These have served as the touchstones for sustainable maritime operations and reference points in the preservation of marine life, a roadmap to the promotion of environmentally responsible shipping. The level of collaboration these have brought to the table, with industry stakeholders, governments, and environmental organizations working together, has never been witnessed before—a strong testament to what can be done collectively in the face of complex environmental challenges.
The aim of the current research was to explore the measurement methodologies according to ISO 17208-1 Standard. In addition, a serious investigation was done regarding the instruments' capabilities as well as measurement ranges, standard deviations, calibration and verification intervals, and uncertainties of instruments of a measuring kind—hydrophones and data analyzers together with devices for distance measurements including also a detailed summary derived from Standard-related documentation. The tables given in ISO 17208-1 were extended and modified to embrace a wider view. The normative conditions of the trial, including the procedures for hydrophone deployment and the maneuvers to be performed by the vessel being tested, were specified. In addition, the methods used to process the data obtained from such measurements were fully discussed, including the addition of background noise to the measurement data and the conversion of raw data to reliable results. The sources of the noise were carefully identified and clear summaries and related solutions for different situations were given. Furthermore, potential future developments regarding the subject were discussed based on an analysis of the recent status of shipbuilding in Turkey, and a few suggestions regarding technological improvements were put forward comprehensively. Within this scope, a conclusion was stated regarding academic and practical contributions to innovations within the sector.
In my work, different measurement methodologies were reviewed in line with the ISO 17208-1 standard, paying close attention to the specific requirements and best practices associated with underwater noise assessments. The functionalities, measurement capabilities, standard deviations, calibration and verification intervals, and the measurement uncertainties of the instruments used—hydrophones, data analyzers, and distance measuring devices—were analyzed and synthesized in the light of the standard's guidelines. Special emphasis was given to the defined specifications of the various categories of equipment, such as the sensitivity, accuracy, and reliability of hydrophones and data analyzers, and most importantly, the critical role that calibration plays in ensuring valid outcomes. The standard's guidelines were also examined with regard to strategies to minimize errors in data collection, including optimal placement of hydrophones and adjustment in cable lengths.
The tables in ISO 17208-1 have been meticulously redeveloped and rewritten, now presenting a condensed coverage that is more relevant, along with the inclusion of supplementary parameters and examples to depict more realistic testing scenarios. To ensure clarity and reproducibility, the test conditions were specified: for instance, the required mounting of the hydrophones, the operational configuration, and the particular maneuvers that the ship undergoing the test is expected to perform. For instance, hydrophone place geometry considering the effect it may bring on measurement accuracy; the necessity of controlled maneuvers such as a straight-line tests and turning radius evaluations in respect of accuracy of data, and,
Methods which were adopted in processing data emanating from these sets of measurements, including fully discussed ones dealing with methods of treatment and integration of background noise in measurement data. Methods of discriminating signal noise from ambient noise were discussed in terms of applying systematic corrections and adjustments that included distance, equipment limitations, and environmental parameters. One of the important aspects was the conversion of raw data into reliable and interpretable results; the equations and procedures described in the standard support the credibility of noise assessments.
Also, some improvement and research directions concerning noise quality and the competitive character of the present state of Turkish shipbuilding have been identified. Proposed countermeasures included the use of quieter propulsion systems, improved hull forms, and advanced coatings that can reduce the noise levels.