IMO Seeks Affordable Underwater Noise Monitoring for Ships
A new proposal to the International Maritime Organization (IMO) seeks to reduce the cost of underwater radiated noise (URN) measurement across the global shipping fleet. The initiative aims to establish a more affordable and practical monitoring system, helping shipowners meet environmental requirements while supporting marine pollution prevention and sustainable shipping.
Submitted for consideration at the IMO’s 85th Marine Environment Protection Committee (MEPC 85) session, the proposal is jointly supported by the International Chamber of Shipping (ICS), BIMCO, the International Parcel Tankers Association (IPTA) and RINA. It recommends establishing autonomous measurement facilities at major international shipping routes to assess vessel noise emissions during normal operations.
Under the IMO’s Revised Guidelines (MEPC.1/Circ.906/Rev.1), direct measurement is the preferred method for establishing a ship’s underwater radiated noise baseline. Such measurements are also normally required for classification society quiet ship notations. However, the financial and operational demands of dedicated sea trials remain a significant barrier to wider implementation.
Dedicated underwater noise measurement trials are estimated to cost USD 30,000–50,000 per vessel. When vessel diversions and lost revenue are included, total expenses can rise to USD 40,000–250,000 per ship. For a global fleet of approximately 100,000 vessels, one round of measurements could therefore cost between USD 4 billion and USD 25 billion. Global capacity is currently estimated at only around 50 dedicated trials annually, while repeat measurements may also be necessary.
To address these limitations, the proposal recommends autonomous monitoring facilities at major maritime chokepoints, including the Suez Canal, Panama Canal, Strait of Gibraltar, Strait of Malacca, Taiwan Strait and English Channel. Ships passing through these locations could undergo underwater noise monitoring without undertaking separate measurement voyages.
An illustrative network of five facilities is estimated to require an initial capital investment of USD 0.8–1.8 million, with annual operating expenses of USD 0.7–1.4 million. This translates into capital costs of less than USD 20 per ship and annual operating costs below USD 15 per ship. Additional ship-specific data verification and reporting would cost approximately USD 4,424 per vessel.
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The proposal also highlights the need for an ISO standard known as “Measurement of Opportunity” to ensure consistent and reliable results. The standard would need to meet the technical requirements for quiet ship notations while allowing repeatable measurements to track changes in vessel noise emissions. The proposed monitoring network could be established within approximately four years.
Autonomous facilities would not provide complete coverage, particularly for vessels operating on short-sea routes. The proposal therefore identifies onboard measurement systems, drone-deployed sensors and predictive modelling as complementary approaches for monitoring underwater noise across different shipping operations.
The financial implications also extend to maritime environmental incentive programmes. Previous case studies indicate that measurement costs below USD 15,500 could make participation in schemes such as the Environmental Ship Index (ESI), Green Marine, Green Award, PIAQUO and ECHO financially beneficial. More accessible baseline measurements would help shipowners evaluate the performance of noise-reduction measures and make informed decisions about environmental investments.
The co-sponsors are calling on the IMO to recognise the importance of economically viable underwater noise baseline measurements. They have also invited further proposals on technically feasible approaches and recommended that the terms of reference for any future URN Working Group address affordable measurement options and implementation timelines.
The proposal is expected to contribute to discussions on the implementation of the IMO’s underwater radiated noise guidelines, with the broader objective of making marine environmental monitoring more accessible to the international shipping industry.
