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. This marine notice supersedes marine notice 2024/01.
Guidance for
- Ship designers
- Shipbuilders
- Shipowners
- Ship operators
- Maritime authorities
- Suppliers
- Manufacturers
- Classification societies
- Other relevant maritime industry stakeholders
Background
Due to increasing concerns with the impacts of underwater radiated noise (URN) from commercial shipping on marine life, the Marine Environment Protection Committee (MEPC) released revised guidelines for the reduction of URN from shipping, which took effect on 1 October 2023. 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.
- 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
- evaluating various technological, operational, and maintenance approaches to reduce URN. Model templates in the revised guidelines help shipowners and designers in this process.
Update:In 2024, the MEPC approved amendments to the [Revised URN Guidelines (MEPC.1/Circ.906/Rev.1) PDF**470.32 KB](https://www.amsa.gov.au/sites/default/files/2025-06/MEPC1-Circ906-Rev1-Revised-Guidelines-For-The-Reduction-Of-Underwater-Radiated-Noise-From-Shipping.pdf), to include a URN management planning reference chart to support the preparation and implementation of URN management planning.
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 greenhouse gas emissions from ships or other IMO measures associated with ship safety.
Incentive schemes
Maritime authorities, financial and insurance institutions and others are encouraged to support URN reduction efforts and monitoring by promoting the establishment of incentive schemes. Such schemes could be linked to:
- URN ship class notations
- recognition of URN management plans
- URN reduction targets
- ship and engine technologies and maintenance
- ship speed optimisation programs
- voluntary sustainability certifications, which include evidence of URN reduction. Examples of incentive schemes include discounts on port dues, fairway fees, extra services, or promotional benefits.
Further information
Download a copy of [MEPC.1/Circ.906 Rev.1 PDF**470.32 KB](https://www.amsa.gov.au/sites/default/files/2025-06/MEPC1-Circ906-Rev1-Revised-Guidelines-For-The-Reduction-Of-Underwater-Radiated-Noise-From-Shipping.pdf) setting out these revised guidelines.
Note:The above circular revokes MEPC.1/Circ.833 and MEPC.1/Circ.906.
- [Print](https://www.amsa.gov.au/node/13530/printable/print)
- [Print](https://www.amsa.gov.au/node/13530/printable/print)
Last updated: 10 June 2025