The Quieter Tug – Designing for Underwater Noise

November 3, 2023

By Giorgio Burella, EIT, Ph.D.

While noise control is a hallmark of tugs designed by Robert Allan Ltd., in recent years we’ve learned that Underwater Radiated Noise (URN) from ships is responsible for tremendous stress on underwater life. Noise has been found to reduce the ability to communicate, forage and ultimately thrive for a variety of marine fauna and non-migrating species, such as the local Southern Resident Killer Whales (SRKW) here in southern British Columbia (BC), are even more at risk.

Robert Allan Ltd. has been actively at the forefront of this issue, developing tools to quantify the radiated URN and its impact on marine life. The TugEm (Tug Emissions) tool has been developed to predict the URN from vessels over a specified operational profile, discretize the machinery and propeller components and produce metrics of the impact on marine fauna. The predictions can also account for the effects of applying noise reduction solutions. This way, Robert Allan Ltd.’s designers can guide clients in selecting the equipment that most reduce the vessels’ URN signature.

TugEm is still in its development, and extended validation with real-world data is underway. Therefore, an extensive URN measurement campaign is set to start this summer under the Quiet Vessel Initiative and the Clean Transportation System project funded by Transport Canada. The trials will focus mainly on the battery-electric ElectRA tugs that will operate in BC. A dedicated hydrophone station will be temporarily installed to measure URN during the planned trial runs. The collected data will support Robert Allan Ltd. in validating TugEm, understanding the prevalence of the onboard URN sources and assisting our tug operator partners in assigning a quiet URN class notation on the ElectRA vessels.