Ship noise


Ship noise can have negative impacts – on both humans and marine life.

Noise on ships

Continuous noise onboard ships can have an adverse impact on human health. IMO adopted, in 2012, a regulation in the International Convention for the Safety of Life at Sea (SOLAS) to require ships to be constructed to reduce on-board noise and to protect personnel from noise, in accordance with the Code on noise levels on board ships. The Code sets out mandatory maximum noise level limits for machinery spaces, control rooms, workshops, accommodation and other spaces on board ships.

The International Labour Organization’s Maritime Labour Convention (MLC 2006) also has requirements with respect to preventing the risk of exposure to hazardous levels of noise on board ships. 

Underwater noise and impact on marine mammals

Studies have shown that underwater-radiated noise from commercial ships may have both short and long-term negative consequences on marine life, especially marine mammals. The issue of underwater noise and impact on marine mammals was first raised at IMO in 2004. It was noted that continuous anthropogenic noise in the ocean was primarily generated by shipping. Since ships routinely cross international boundaries, management of such noise required a coordinated international response.

Guidance on reducing underwater noise

In 2014, IMO's Marine Environment Protection Committee (MEPC)  approved guidelines on reducing underwater noise from commercial shipping, to address adverse impacts on marine life. Given the complexities associated with ship design and construction, the Guidelines focus on primary sources of underwater noise, namely on propellers, hull form, on-board machinery, and various operational and maintenance recommendations such as hull cleaning.

Much, if not most, of the underwater noise is caused by propeller cavitation (the formation and implosion of water vapour cavities caused by the decrease and increase in pressure as water moves across a propeller blade - cavitation causes broadband noise and discrete peaks at harmonics of the blade passage frequency in the underwater noise spectrum). On-board machinery and operational modification issues are also relevant.

The Guidelines also include definitions and underwater noise measurement standards.

When agreeing the Guidelines, it was noted that there were still significant knowledge gaps, and that sound levels in the marine environment and the contribution from various sources was a complex issue, so setting future targets for underwater sound levels emanating from ships was premature and more research was needed, in particular on the measurement and reporting of underwater sound radiating from ships. The Committee invited interested Member Governments to submit proposals to a future session.

Review of the guidelines

Following instruction from the MEPC in 2021, the IMO Sub-Committee on Ship Design and Construction (SDC 8), which met in remote session 17-21 January 2022, began its work to review the 2014 Guidelines. 

The aim of the review is to provide updated recommendations based on the latest developments in ship design and technology and to address the barriers to their uptake in an effort towards a significant and measurable reduction of underwater-radiated noise from ships.

A working group at SDC discussed a number of submitted documents and developed a work plan and terms of reference for a correspondence group, which were agreed. 

The correspondence group is tasked with, inter alia: enabling engagement of Inuit and other indigenous communities and the incorporation of Indigenous Knowledge; identifying comparable and common means of measuring, analysing and reporting of underwater radiated noise emissions from ships (e.g. existing and developing ISO and other international standards); identifying actions to further prevent and reduce underwater noise from ships, including options to integrate new and advancing technologies and/or vessel design solutions taking into account geographical characteristics; considering the impact and interrelation of the proposed actions in the context of achieving other regulatory goals, including ship safety, energy efficiency, as well as the vision and mandate of the Organization to reduce pollution from ships; amending the 2014 Guidelines; considering ways to promote the work of the Organization to increase the awareness, the uptake and implementation of the Guidelines and identifying the most appropriate tools to do this; identifying areas that require further assessment and research; considering the next steps; maintaining and update a list of reports and documents provided in a submission to the Sub-Committee to produce a new Compendium on Underwater Noise from Commercial Shipping.

The work plan envisages that recommendations for the next steps to be undertaken to establish international solutions for the reduction of underwater noise could be submitted to the Marine Environment Protection Committee (MEPC 80) in 2023.

The Sub-Committee endorsed the Working Group's recommendation to invite all relevant IMO bodies to note the work on underwater radiated noise, in particular, where there are linkages, impacts or co-benefits.

Global Partnership for Mitigation of Underwater Noise from Shipping

A  project bid to the Global Environment Facility by the IMO's Secretariat's Department for Partnerships and Projects (DPP) has been submitted (as at January 2022). This bid is to seek funding for a project ("Global Partnership for Mitigation of Underwater Noise from Shipping (GloNoise Partnership)"), with the overall objective to establish a global stakeholders' partnership, with a strong developing countries' focus, in order to deal with underwater noise from shipping.

Particularly Sensitive Sea areas and routeing measures

The issue of underwater noise and its effects on marine life is also taken into account through IMO adopted “Particularly Sensitive Sea Areas” (PSSAs). These are areas considered to deserve special protection, due to their recognized ecological or socio-economic or scientific significance, and which may be vulnerable to damage by ships. Ship routeing measures can be proposed for adoption in connection with a PSSA, to protect marine life.

IMO has also adopted a series of routeing measures to protect whales and other cetaceans from ship strikes during breeding seasons, by keeping ships away from specified areas. So these measures may also have a positive effect in terms of reducing the impacts of underwater noise. (Click for the article: Routing for Whales.)

Noise from dredging

Noise has also been discussed in the context of the work of the London Convention and Protocol on the protection of the marine environment from pollution from dumping of wastes and other matter. Dredging activities – dredged material is the main source of permitted wastes dumped at sea under these treaties - are also a source of anthropogenic noise.

The World Dredging Association (WODA) has submitted technical guidance on underwater sound in relation to dredging activities to the London Convention and Protocol Scientific Groups, providing advice to decision-makers, stakeholders and scientists on how to manage impacts of underwater sound, primarily from dredging.

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