New IMO Guidelines Aim To Reduce Underwater Radiated Noise From Ships

With growing global concern over the impact of underwater radiated noise (URN) on marine ecosystems, the IMO’s Marine Environment Protection Committee (MEPC) has released revised URN reduction guidelines, effective from 1 October 2023.

These updated measures provide critical technical, design, operational, and maintenance guidance for ship designers, builders, owners, operators, classification societies, maritime authorities, and other industry stakeholders.

Broader Scope and Applicability

The revised guidelines apply to both new and existing ships, focusing on reducing URN through a comprehensive lifecycle approach:

• Design and construction considerations

• Operational best practices

• Maintenance procedures

They also align with updated international measurement standards and classification society rules, facilitating better evaluation and monitoring of URN reduction efforts.

URN Management Planning: A Proactive Step

A significant addition in the new guidelines is the emphasis on URN management planning, especially for new builds and, where feasible, existing vessels. Key components of a URN management plan include:

• Establishing a baseline URN level

• Setting realistic reduction targets

• Assessing technological, operational, and maintenance strategies

Model templates are provided to assist stakeholders in customizing their plans effectively. In 2024, MEPC further strengthened this approach by including a URN Management Planning Reference Chart under MEPC.1/Circ.906/Rev.1.

Aligning URN Reduction with Energy Efficiency Goals

The updated guidelines recognize that improvements in energy efficiency may also reduce URN. A dedicated section highlights positive synergies with climate policies, though it emphasizes that URN reduction must not hinder efforts to lower greenhouse gas emissions or compromise ship safety under IMO frameworks.

Incentive Schemes to Encourage Adoption

Maritime authorities, port operators, insurers, and financial institutions are encouraged to support URN reduction through voluntary incentive programs, such as:

• Discounts on port dues or fairway fees

• Recognition of URN ship class notations

• Rewards for ships with URN management plans or voluntary certifications

• Support for ship speed optimization programs and quiet propulsion technologies

These incentives aim to promote voluntary compliance and accelerate adoption across the industry.

The revised IMO guidelines offer a practical, flexible framework for reducing underwater noise pollution, protecting marine life while encouraging innovation, planning, and cross-sector collaboration. With the inclusion of URN management planning and alignment with energy efficiency and climate objectives, these updates represent a crucial step toward sustainable shipping. Active participation from all maritime stakeholders will be key to achieving long-term noise mitigation goals.