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Next steps identified on Underwater Radiated Noise (URN) at IMO

Published on 6 February 2024

As previously shared in September 2023, the 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).

Following on from this, the IMO Sub-Committee on Ship Design and Construction has considered its next steps where it was agreed that the work in this area will now be entitled ‘Experience Building Phase for the Reduction of Underwater Radiated Noise’ with a target completion year of 2026.

At the 10th meeting of the IMO Sub-Committee Ship Design and Construction (SDC 10), attended by IMCA, the following views were expressed:

  1. While there were merits in standardising URN management planning/measurements methods, standardisation should not limit the evaluation of the amount of URN reduction to only one fixed operational methodology.
  2. The development of training guidance for seafarers to raise broader awareness of URN was supported.
  3. Indirect measurements of URN were a pragmatic approach but required validation against direct measurements.
  4. With respect to potential conflicts between GHG reductions measures and those for URN reductions, shipowners, designers, and suppliers should be dissuaded from practices which lead to such conflicts; the best compromise of URN and GHG reductions should be endeavoured, not only by design considerations but also by a combination of both the design aspect for GHG reductions, such as propeller design, and operational measures, such as speed reduction in certain vulnerable sea areas.
  5. It is important to have a common understanding on the methodology used to estimate the amount of URN reduction from the various measures introduced to enable a consistent evaluation of the URN reduction in different phases of a ship life, from its design and construction phase to the operation phase.
IMCA Contact

Margaret Fitzgerald
Head of Legal & Regulatory Affairs

A draft action plan was agreed which aims to further prevent and reduce URN from ships. A three-year experience-building phase (EBP) was agreed, with the possibility of an extension up to two years, if necessary for specific initiatives (e.g. new ship builds), to be determined by the end of the third year.

The main objectives of the EBP are to collect information on lessons learned and best practices in the application and the uptake of the Revised Guidelines (MEPC.1/Circ.906) by ship designers, builders, owners, and operators to reduce the URN of any given ship and other stakeholders in establishing mechanisms and programmes through which noise reduction efforts can be realised, to further prevent and reduce URN from ships.

A guidance document for the EBP has been developed which identifies the key areas to be considered:

  1. URN Management Planning, including URN baselining, management plan development and target setting.
  2. Design and technical noise reduction approaches.
  3. Maintenance and operational approaches.
  4. Energy efficiency and URN reduction.
  5. Evaluation and monitoring.
  6. Incentivisation.
  7. Training and raising awareness.

Commenting on the next phase of activity around URN at the IMO, Margaret Fitzgerald, Head of Legal and Regulatory Affairs, IMCA said: “Following on from previous activity around Underwater Radiated Noise at the IMO, we now have an important target date of 2026 for the next phase which will collect the lessons learned and share best-practice from a range of maritime stakeholders – ship designers, builders, owners, and operators – in their application of the Revised Guidelines. This work is crucial as we move into an implementation phase.”

“The MPRA Committee is following this issue closely and will provide further updates to Members as work progresses at the IMO.”

In addition to covering URN, the IMO Sub-Committee also discussed the implementation of the Industrial Personnel (IP) Code and the situation in the Red Sea.