Reducing Underwater Noise from Large Commercial Ships: a response to P.F. Pittenger (original) (raw)
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Acoustic impact of ships: noise-related needs, quantification and justification
The evaluation of the acoustic impact of ships is a complex problem, involving not only different sources but also different kinds of receivers and transmission paths. The problem of health and comfort for crew and passengers on board has been considered since a few decades, leading to quite a structured and detailed framework of Norms and Requirements. On the other hand, only in recent years a growing attention has been devoted to air-borne noise emissions outside the ship, for which requirements are not present. Underwater noise emissions have, even more recently, gained attention for their potential interference with mammals' communications and with the sophisticated use such animals make of acoustic signals for interacting with their living environment. An aim of the present work is to review the state of the art in the three areas above identified outlining the differences in the specific fields as regards: the present knowledge of the phenomena involved; the accuracy of the models available for the description of noise propagation; the accuracy of the models available for the quantification of noise effects.
Reducing Underwater Noise from Large Commercial Ships: Current Status and Future Directions
Who should read this paper? If your employment relates to a marine industry, this paper might brief you on the contents of your next staff meeting. If you own, operate, or work on a vessel, and are subject to IMO legislation, this paper certainly concerns your interests. If you are casually interested in the ocean, or feel a concern for communities of cetaceans and other marine fauna, go ahead and sate your curiosity about ocean noise. Why is it important? You may have heard the clamour about anthropogenic ocean noise. Citing new legislation as adding pressure to a growing consensus against ocean noise, this paper is a clear interpretation of the facts and offers recommendations which suit them. Given the historically diverse nature of the marine community and the consequent challenges to its regulation, the field of ocean noise regulation appears a decentralized, overwhelmed, unmanageable branch. This research ignores the noise and picks up the signal; that is, it focuses on reasonable priorities to create tangible results with detailed explanations for how identifying problem vessels can be done efficiently, along with solutions and how to implement them. (Spoiler alert: check your propeller.) This review and, in essence, proposal features technologies that are already commercially available. The authors emphasize the potential for reducing noise levels alongside improvements in fuel efficiency, offering a benefit to mariners for pursuing quieting measures. At a time when there is a lot of racket over ocean noise, this paper sounds calm and rather relaxing.
Relationship between ship type and underwater noise emissions
Concerns that shipping noise could affect marine mammals were raised as early as the 1970s. This was based on the observation that there was a considerable band overlap between the spectra of frequencies used by large Baleen Whales and the major components of noise from the propellers of commercial vessels. This is a very serious threat to the species, since they rely almost entirely on sound waves for communication and hunting. Baleen Whales aren’t the only species affected by shipping noise either, the noise has been observed to cause avoidance behaviours and stress in many other species of fish, in addition to interfering with communication. Out of all the frequencies, elevated noise levels that lie in the 10-300 Hz range have the ability to mask biologically generated sounds. With the increase in global shipping over the last few decades, oceanic ambient noise levels have been rising correspondingly. The NOAA has found evidence that underwater sound has been doubling every 10 years with most of the sound being anthropogenic. These increases amount to 20 dB from the pre-industrial era to the modern age. In the vicinity of major shipping routes, increases in noise can be much larger. Propeller cavitation seems to be the predominant noise source on-board maritime vessels and propeller singing can potentially cause emissions of high-pitched noise. Improved propeller design e.g. anti-singing trailing edge, and efficient wake flow may serve to reduce acoustic emissions. For merchant vessels, it is necessary to accept a certain amount of cavitation in the propeller, at present, because designs that eliminate cavitation reduce efficiency drastically. It is probable that, statistically, one-tenth of the noisiest ships generate a major portion of the net impactful noise undersea. In recent times, international policy making bodies have begun taking environmental concerns very seriously, and although there is no internationally accepted standardization document that guides shipbuilders on crafting less noisy vessels yet, there are two important standards that aid underwater noise measurement.
Requirements for Reducing Underwater Noise From Ships
IEEE Journal of Oceanic Engineering, 2017
Awareness of underwater noise from shipping has grown significantly within the marine community over the past decade. Concerns have been raised about the levels of anthropogenic noise in the world's oceans, as well as in harbors and areas with sensitive or protected marine life. Regulatory bodies are listening, and are considering what actions are available to reduce noise. Measurements of vessel noise in various situations have been performed to better quantify the problem, and efforts have been made by some to correlate noise levels with simplified vessel parameters. Such efforts provide insights into what levels of noise are possible and how they are related to ship operation. However, to reduce underwater noise, a deeper understanding of specific vessel design and factors that lead to noise are required. While generalities of primary noise sources can be applied to different classes of vessels, design details of specific vessels must be obtained and analyzed to implement noise reductions. Armed with knowledge of vessel details, noise control strategies can be optimized using various computer-aided tools. This must be done on a case-by-case basis for different vessel designs, and is most efficient and effective for new builds. Costs for such efforts must also be considered if vessel noise is to be made inherently quieter worldwide.
Sustainable Maritime Transportation and Exploitation of Sea Resources, 2011
The evaluation of the acoustic impact of ships is a complex problem, involving not only different sources but also different kinds of receivers and transmission paths. The problem of health and comfort for crew and passengers on board has been considered since a few decades, leading to quite a structured and detailed framework of Norms and Requirements. On the other hand, only in recent years a growing attention has been devoted to air-borne noise emissions outside the ship, for which requirements are not present. Underwater noise emissions have, even more recently, gained attention for their potential interference with mammals' communications and with the sophisticated use such animals make of acoustic signals for interacting with their living environment. An aim of the present work is to review the state of the art in the three areas above identified outlining the differences in the specific fields as regards: the present knowledge of the phenomena involved; the accuracy of the models available for the description of noise propagation; the accuracy of the models available for the quantification of noise effects.
A Simple Model for the Underwater Noise Source Level of Ships
2014
Underwater noise becomes a field of growing concern because of the possible interaction with sound vocalization of marine mammals. Modeling the effect of shipping noise being a predominant contribution worldwide requires more than statistics of measured ships in the field. This article is an attempt to characterize the underwater radiated noise level of a ship by relating spectral components of noise to naval architectural features of the ship.
IEEE Journal of Oceanic Engineering, 2017
There is increasing concern within the scientific community about the underwater noise due to anthropogenic activity and its impact on marine life, with negative consequences on biodiversity and sea resources. In that context, the European Marine Strategy Framework Directive stated in 2008 that the anthropogenic noise due to shipping was to be mitigated. To address this issue, the European Union (EU) project "Achieve QUieter Oceans by shipping noise footprint reduction" (AQUO) (www.aquo.eu) started in October 2012 with a duration of four years. The project brought together experts from shipbuilding, underwater acoustics, and bioacoustics, with a multidisciplinary approach. In this paper, after giving a brief overview of the project structure, the methodology proposed by the AQUO project to set guidelines for controlling the underwater noise from commercial shipping is presented in more detail. Such a methodology is aimed at identifying the most promising strategies for the mitigation of the impact of shipping noise on marine fauna. Different technical as well as operational solutions are evaluated by taking into account the impact on marine life, the feasibility in terms of ship design, and the cost effectiveness, also considering fuel efficiency. While technical solutions are usually more effective at the design stage both in terms of costs and performance, operational solutions can potentially be adopted without any modification to the existing fleet. Furthermore, operational prescriptions can be set by national/local authorities who cannot directly intervene on ship configurations. The different solutions have been evaluated by means of numerical modeling carried out by using a Noise Footprint Assessment Model derived from the Quonops tool.
Normative framework for ship noise: Present and situation and future trends
Noise Control Engineering Journal, 2012
The paper addresses the present regulatory framework regarding ship noise 5 emissions both towards the internal spaces onboard and the external environ-6 ment (in air and in water). A different level of development has been reached 7 in the various areas for the definition of the needs for the noise control and 8 for their implementation in a normative framework. This is due in part to the 9 different point in time in which the different aspects were recognised to be 10 relevant and therefore studied, assessed and regulated. The analysis of existing 11 regulations is the basis for considering the present situation, on-going develop-12 ments and possible future trends as regards the evaluation of ship noise impact 13 on the various types of environment. The situation of the requirements developed 14 for the maritime field appears to be in line with other fields of engineering as 15 regards the definition of noise limits for the working environment, while the 16 definition of comfort of living on board seems to be somehow lacking behind 17 other fields, with possibility of taking advantage of their experience. Well estab-18 lished assessment procedures for external radiation in air appear to be not yet 19 available and in this case a need for specific developments arises. Finally, 20 for underwater noise emissions, there is availability of relatively well developed 21 requirements, that however are not adequately correlated to the quantification 22 42 harbours, while underwater noise affects the ocean envi-43 ronment and the marine fauna. Recent studies suggest 44 that a large percentage of people living in urban areas 45 close to harbours R1 1 and a number of marine species, at 46 different evolutionary levels R2 2 , suffer from ship noise 47 emissions. Underwater noise emissions are clearly typi-48 cal of ships and pose specific questions, given the differ-49 ent transmission medium and the different kind of 50 receivers, but the other aspects of the assessment of 51 the ship noise impact, too, have peculiar characteristics 52 in comparison with other vehicles, related to the dimen-53 sions and complexity of the ship structure, to the variety 54 of sources and operational conditions on board, to the 55 relative positions of sources and people affected and to 56 the generally higher time duration of exposures (for 57 internal noise). 58
Normative framework for ship noise: Present situation and future trends
2012
The paper addresses the present regulatory framework regarding ship noise emissions both towards the internal spaces onboard and the external environment (in air and in water). A different level of development has been reached in the various areas for the definition of the needs for the noise control and for their implementation in a normative framework. This is due in part to the different point in time in which the different aspects were recognised to be relevant and therefore studied, assessed and regulated. The analysis of existing regulations is the basis for considering the present situation, on-going developments and possible future trends as regards the evaluation of ship noise impact on the various types of environment. The situation of the requirements developed for the maritime field appears to be in line with other fields of engineering as regards the definition of noise limits for the working environment, while the definition of comfort of living on board seems to be somehow lacking behind other fields, with possibility of taking advantage of their experience. Well established assessment procedures for external radiation in air appear to be not yet available and in this case a need for specific developments arises. Finally, for underwater noise emissions, there is availability of relatively well developed requirements, that however are not adequately correlated to the quantification of the effects of the noise emissions on the marine fauna.
The SOUNDS project: towards effective mitigation of underwater noise from shipping in Europe
Proceedings of Meetings on Acoustics
Continuous underwater noise from shipping has been identified as one of the main contributors to ambient noise levels in the oceans. Notwithstanding the potential impacts on marine life, the subject started receiving attention from international and regional regulatory bodies only very recently. Last year, the European Maritime Safety Agency commissioned a study to consolidate information about continuous underwater noise from shipping in order to derive recommendations for a future multi-stakeholder strategy within Europe. The work reviewed information about sources of continuous noise, environmental impacts, the policies in place to manage underwater noise and available mitigation measures to reduce noise levels. Effective management of underwater noise from ships is a multi-sectoral challenge requiring coordination between different policies and stakeholders. Based on an online survey and a number of interviews, it was possible to elucidate: 1) how different stakeholders interact; 2) the main drivers for addressing underwater noise; and 3) possible strategies for tackling the subject effectively. Additionally, considerations and lessons learned from ECHO program in Canada were analysed as a case study. The paper will describe the main activities carried out in the project, focusing on recommendations for effective mitigation of ship noise.