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.
In 2008, the IMO Marine Environment Protection Committee (MEPC) agreed to develop non-mandatory technical guidelines to minimize the introduction of incidental noise from commercial shipping operations into the marine environment to reduce potential adverse impacts on marine life.
Guidance on reducing underwater noise
In 2014, IMO 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 adopting 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.
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.)
Current work on underwater noise at IMO
The Marine Environment Protection Committee (MEPC) at its 72nd session in April 2018 noted a number of submissions in relation to underwater noise. The need for further research to better understand the impact of underwater noise from shipping as opposed to underwater noise from other sources was raised by a number of delegations.
Member States have been encouraged to continue to share their experiences in dealing with the reduction of underwater noise from shipping.
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.
- Download the IMO Guidelines on reducing underwater noise from commercial shipping.
- Submission on IMO's work on anthropogenic underwater noise to the 2018 nineteenth meeting of the United Nations Open-Ended Informal Consultative Process on Oceans and the Law of the Sea, on "Anthropogenic underwater noise" (18-22 June 2018).
- Expert Workshop on Underwater Noise and its Impacts on Marine and Coastal Biodiversity (2014) – report and submissions can be downloaded here.
- Understanding Anthropogenic Underwater Noise (Canada) - https://www.tc.gc.ca/eng/anthropogenic-underwater-noise.html
- Listen to whale sounds and whale calls being masked by the sound of a large ship passing by a pod on the Port of Vancouver website.
- Ocean noise page (NOAA) - https://oceanservice.noaa.gov/facts/ocean-noise.html
- Underwater sound in relation to dredging (Central Dredging Association (CEDA))
IMO and the Oceans: IMO’s work to address noise from commercial shipping and its adverse impact on marine life is relevant to the UN Sustainable Development Goal (SDG) 14 on the oceans.