Bold Strides Towards URN Reduction
Oct. 7 2019
Imagine that whenever you ate, slept or made a phone call, a nearby construction team pulled out their jackhammers and started working. This is the everyday experience of countless marine creatures. Whales, dolphins, seals and millions of other underwater species are routinely affected by Underwater Radiated Noise (URN).
In-service ships emit a wide range of frequencies that can hinder animals’ abilities to communicate, hunt, migrate and echolocate. In the past decade, the global shipping community has begun to take action, by measuring and identifying ways to reduce URN.
A comprehensive understanding of URN
URN was first recognized on a global scale in 2008, when the Marine Strategy Framework Directive (MSFD) began devising a plan to reduce underwater noise. By 2013, IMO had produced non-mandatory URN guidelines, and class societies like Bureau Veritas began developing URN notations.
In the last decade, Bureau Veritas has been involved in many URN projects seeking to identify and limit the causes of underwater noise, including two EU-funded R&D projects.
- The first study, SILENV, explored a global approach to investigating noise-related disturbances from maritime transport and aimed to establish an “acoustic green label”.
- The second project, conducted with AQUO, concerned methods for assessing the noise footprints of individual vessels and overall ocean shipping. Bureau Veritas also participated in a series of marine sound workshops organized by the Observatory for Responsible Innovation, with the goal of investigating ways of measuring URN and proposing a standardized methodology.
Tackling engine and propeller noise
Thanks to research, the maritime industry has pinpointed the primary onboard URN offenders: engines and propellers. Together, these two pieces of equipment cover the spectrum of underwater sound disruption: engines vibrate at a low frequency, which disturbs large sea animals, and propellers produce high frequencies, which harm smaller marine creatures.
Bureau Veritas has worked on numerous joint projects to develop solutions for retrofitting vessels and improving newbuilds. Bureau Veritas Solutions – Marine & Offshore technical experts have created predictive calculations for noise and vibration, which are used to determine vessel improvements.
There are many available routes to minimizing URN. Regarding engine noise, ships can improve insulation by adding acoustic enclosures, disperse radiated noise by widening engine stiffeners, and limit noise by adding dampeners to small engines and affixing damping plates. For propellers, technical experts can investigate optimal blade designs, conducting hydrodynamic tests to assess propeller efficiency and reduced cavitation.
Efficient approaches to reducing URN
Ships vary greatly in terms of size, structure, equipment, distance traveled and frequency of use. Certain solutions for URN must be customized to the vessel, and this requires ship evaluations, which can be costly and time-consuming. For this reason, some shipowners have been slow to order assessments and/or alter their vessels.
Classification societies are tackling these concerns, searching for efficient solutions that provide shipyards and shipowners further incentives to reduce URN. For example, Bureau Veritas Solutions M&O engineers are using Computational Fluid Dynamics (CFD) to determine the optimal design for propeller blades, allowing vessels to toggle between fuel-efficient and noise minimizing settings.
Bureau Veritas is also working to make ship assessments as efficient as possible and lower overall costs. In 2018, we shortened our noise measuring procedure for ships from the two passages expected for newbuilds during sea trials to one passage. We did this by doubling the number of deployed buoys and corresponding lines of three hydrophones in the water. This limits the time ships spend out of service and provides reliable and transparent data when testing in-service ships. Some shipowners are also taking advantage of retrofit programs designed to improve fuel efficiency to carry out predictive calculations for URN.
Without regulations or other incentives, it can be difficult for shipowners to justify prioritizing URN reduction in terms of short-term ROI. However, shipowners who invest in URN reduction often see strong ROI over the long term, which can quickly eclipse initial costs. Moreover, improving URN addresses concerns related to onboard noise and comfort. For vessels like cruise ships and ferries, which are subject to high standards for voyage comfort, limiting ship vibration is crucial for passengers and crew members.
Dealing with underwater noise and vibration is not solely one initial cost: it is linked to the rest of the ship and design, and is part of overall noise and vibration management. If you do it properly, you can address underwater noise and vibration at the start and boost comfort. Propeller efficiency can also be increased by improving design; this reduces underwater noise and vibration as well. The return on investment is thus obvious.
Incentivization and regulation drive change
The push towards incentivizing URN reduction has begun, with several successfully implemented in Canada. The ports of Vancouver and Prince Rupert both launched port tax reductions for improved URN, which offer monetary gains for Bureau Veritas-classed vessels. For example, a large containership could earn $4,000 CAD per call at these ports for introducing URN reduction measures, leading to potential gains of $20,000 CAD per year.
As URN control progresses, MSFD will continue to implement regulations on local and global levels, and IMO guidelines are likely to be updated in 2020, following a series of technical workshops. In the meantime, Bureau Veritas will continue seeking cost-effective solutions for our clients and designing vessels with a greatly reduced URN footprint.
 Seals are Deafened in Noisy Shipping Lanes, The Guardian, May 2, 2017
 Ship’s Noise is Serious Problem for Killer Whales and Dolphins, The Guardian, February 2, 2016
 SILENV (Ships Oriented Innovative Solutions to Reduce Noise & Vibrations), European Commission Cordis, November 11, 2012
 Guidelines for Regulation on UW Noise from Commercial Shipping, Aquo.eu, November 30, 2015
 Racket in the Ocean: International Conference on Underwater Radiated Noise, Observatory for Responsible Innovation, September 10, 2016
 Why It Pays to Slash Underwater Noise and Vibration, PassengershipInfo.com, September 20th, 2018
 Quieting Ships to Protect the Marine Environment: Technical Workshop, IMO Headquarters, London, February 1, 2019