The Naval Architect: January 2019
Sound in the world’s oceans originates from many sources, such as storms, animals, earthquakes, commercial shipping, marine construction, military activities, oil and gas exploration and production, and even clouds of bubbles. Sound travels through water far better than does light, which is why many marine organisms rely on their hearing to find prey, to avoid predators, and to communicate.
Measurements taken over the last 50 years indicate an increase in some areas in anthropogenic noise emissions into the marine environment. The main sources include vessel traffic, seismic exploration, industrial activities and construction (e.g., pile driving, drilling, tunnel boring, dredging), military and commercial sonar, acoustic deterrent devices, oceanographic experiments, and explosions for underwater construction. While high intensity, impulsive noise sources, such as seismic testing and pile driving, are thought to pose the greatest risk of acute injury (Southall et al., 2007), lower levels of continuous, chronic noise have created serious health impacts for marine mammals. The largest contributor of anthropogenic noise to the marine environment is conclusively commercial shipping, particularly in the low frequency range (Ross, 1993, 2005; Andrew et al., 2002; McDonald et al., 2006, 2008; Hildebrand, 2009; Chapman & Price, 2011; Frisk, 2012).
Underwater noise from commercial shipping has the potential to adversely impact a variety of aquatic animals including whales, fish, turtles and invertebrates, that use sound to communicate, navigate and forage. For Canada, one species in particular – the southern resident killer whale (SRKW) – is facing imminent threats to its survival and recovery, with one of these key threats being underwater noise from vessels. This has prompted the Government of Canada to take action.
Since 2017, Canada has been taking a leadership role in advancing discussions and actions on reducing underwater noise from vessels to better protect the marine environment and help support the survival and recovery of the SRKW. For example, in partnership with the Vancouver Fraser Port Authority’s Enhancing Cetacean Habitat and Observation program (ECHO), and following a pilot project which demonstrated that reducing speeds can result in significant underwater noise reductions, an annual voluntary slowdown in a key area of the critical habitat of the SRKW has been implemented. However, operational measures such as slowdowns are sometimes restricted as a result of geography or due to the classes of ships that transit within a particular area. Quiet ship design and retrofits therefore present an opportunity to address the principal source of underwater noise on a more global scale.
The 2014 International Maritime Organization (IMO) Guidelines for the Reduction of Underwater Noise from Commercial Shipping to Address Adverse Impacts on Marine Life (MEPC.1/Circ.833) (the Guidelines) rightly identify that the largest opportunities for reduction of underwater noise will be during the initial design of a ship. To this end, the Guidelines pinpoint several design areas that are likely to reduce a ship’s underwater noise emission, such as:
- Propellers designed and selected in order to reduce cavitation.
- Ships with a controllable pitch propeller with variability on shaft speed to reduce operation at pitch settings too far away from the optimum design pitch for efficiency.
- Hull forms with appendages designed such that the wake field is as homogeneous as possible.
- On-board machinery and equipment optimised based on its accessibility for regular maintenance and lubrication, as well as its susceptibility to remain in optimal operating conditions.
- Advanced propulsions systems, such as diesel-electric with high-quality electric motors incorporated, instead of conventional less-efficient systems.
- Four-stroke engines (in lieu of 2-stroke engines [when available]) mounted on flexible couplings and resilient mountings.
The IMO’s adoption of the Guidelines has been useful to identify ship designs, technologies, and operations that are likely to reduce underwater ship noise. New additional evidence to support and expand upon them, however, has emerged while certain aspects of ship designs and related technologies are likely to have changed.
Ship design and technology workshop
Canada sees this as an opportunity to leverage and innovate. To gather and share recent research conclusions and assess current and future quiet ship designs, Canada will be hosting an international workshop from 30 January to 1 February 2019 at IMO Headquarters. This workshop presents a unique opportunity to bring together naval architects, marine engineers, ship operators, shipyards, national policy makers, industry associations, academics, and non-governmental organisations to share their breadth of expertise with diverse viewpoints and lead to a more complete and accurate assessment of the current state of, and opportunities for, innovative designs and technology.
This forum will provide an opportunity for international collaboration and allow participants to share the newest research and technical solutions for more quiet ship design and retrofits. The specific objectives of the proposed workshop will include, but are not necessarily limited to:
- Validating current technologies and identifying important gaps and challenges to further progress;
- Assessing areas for innovation potential to determine where more focused research may be needed;
- Understanding and quantifying whether improvements made to ship design for fuel efficiency overlap with improvements made to reduce noise; and
- Documenting the conclusions of the workshop to guide future discussions on reducing underwater ship noise or as groundwork for a review of the existing Guidelines.
For more information on the workshop, including how to register, or if you have any questions about the work that Canada is undertaking in the area of underwater noise more broadly, please do not hesitate to contact Transport Canada at: TC.QuietShips-Naviressilencieux.TC@tc.gc.ca.