Marine notice 2024/01 - Reduction of underwater radiated noise (URN) from shipping

The purpose of this marine notice is to draw attention to the International Maritime Organization’s (IMO) non-mandatory Revised guidelines for the reduction of underwater radiated noise from shipping to address adverse impacts on marine life, which were released on 1 October 2023.


Due to increasing concerns with the impacts of underwater radiated noise (URN) from commercial shipping on marine life, the Marine Environment Protection Committee (MEPC) has released a revised version of the guidelines for the reduction of URN from shipping, following a comprehensive review.

The revised guidelines provide updated design, technical, operational and maintenance guidance to reduce URN, which are applicable to shipbuilders, designers and operators. They are intended to be applied to new and existing ships, taking into account the ship’s design and construction, as well as its operations.

The revised guidelines also include updated international measurement standards, recommendations and classification society rules for the evaluation and monitoring of URN, which will assist in assessing the effectiveness of efforts to reduce URN.

URN management planning

The revised guidelines contain a new section on URN management planning, which should be considered at the earliest stages of design for new builds, and as far as reasonably practicable for existing ships. This includes the development of a URN management plan, intended to be a flexible tool that allows a customised approach. The management plan may include establishing a baseline URN, setting URN targets, and evaluating various technological, operational, and maintenance approaches to reduce URN. Model templates in the revised guidelines help shipowners and designers in this process. 

Energy efficiency and URN

Recognising efforts to achieve increased energy efficiency in ships may also result in a reduction in URN, a dedicated section has been included in the revised guidelines on positive synergies with climate policies. This section notes however that URN measures should not come at the expense of efforts to reduce GHG emissions from ships or other IMO measures associated with ship safety. 

Incentive schemes

Incentive schemes are encouraged to support URN reduction efforts and monitoring. Such schemes could be linked to URN ship class notations, recognition of URN management plans, URN reduction targets, innovative ship and engine technologies and maintenance practices, ship speed optimisation programs, and voluntary sustainability certifications, which include evidence of URN reduction. Examples include discounts on port dues, fairway fees, extra services, or promotional benefits. 

Further information 

A copy of MEPC.1/Circ.906 setting out these revised guidelines can be obtained from the IMO website.  

Please note the above circular revokes MEPC.1/Circ.833. 

Last updated: 22 February 2024