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Limiting Underwater Radiated Noise (URN) at the IMO 

Published on 29 September 2023

Underwater radiated noise (URN) from ships has been proven to have a damaging effect on marine wildlife and even marine plants of many types. Factors which have been identified as contributing to URN, include ship resistance and propulsion together with ship machinery systems and operational approaches. 

For several years the IMO has been working on guidelines to mitigate the effects of URN and in 2014 it approved its first set of guidelines on underwater noise (MEPC.1/Circ.833). Since those guidelines were approved there has been a doubling of noise levels in the ocean. 

IMCA Contact

Margaret Fitzgerald
Head of Legal & Regulatory Affairs

At its’ 80th session, IMO’s Marine Environment Protection Committee (MEPC) approved Revised Guidelines for the Reduction of Underwater Radiated Noise from Shipping to Address Adverse Impacts on Marine Life (MEPC.1/Circ.906) which aims to: 

  1. Provide an overview of approaches applicable to designers, shipbuilders, and ship operators to reduce the URN of any given ship; and  
  2. Assist relevant stakeholders in establishing mechanisms and programmes through which noise reduction efforts can be realised. 

The new Guidelines include updated technical knowledge, including reference to international measurement standards, recommendations and classification society rules. They also provide sample templates to assist shipowners with the development of an underwater radiated noise management plan. 

While the approval of the revised guidelines has been welcomed as a significant step forward in addressing the issue, it is recognised that efforts are now needed to ensure effective uptake of the Revised Guidelines which take effect on 1 October 2023 and supersede MEPC 1/Circ.833. 

Further work will be required, and IMO has set a deadline of 2024. International organisations – such as IMCA – have been invited to submit information on lessons learned/best practices in the implementation of the Revised Guidelines, including outreach and awareness efforts to support uptake, to IMO by MEPC 85 (which will take place in 2025). This information will help to identify any further revisions required to the Revised Guidelines.  

Following the approval of the revised guidelines, MEPC convened an expert workshop on the relationship between energy efficiency and underwater noise in September, with the participation of relevant experts, which IMCA attended.  

Commenting on the new Guidelines and the workshop, Margaret Fitzgerald, Head of Legal and Regulatory Affairs at IMCA, said: “A report produced by Vard for the workshop provided a set of recommendations for future actions. Many of these relate to increased data collection and knowledge dissemination since it has been noted that there is a lack of high-quality, measured data on the effectiveness of many of the methods proposed to reduce URN.”  

“Vard suggests this will increase risk and uncertainty for owners who wish to improve the performance of their ships and could delay any improvement of the overall global fleet.”  

IMCA Members making active progress in this space are invited to get in touch with Margaret.