Vessel Generated Underwater Noise
The META Program is investigating the interconnections between broader energy efficiency and decarbonization initiatives in the maritime sector, with a specific focus on reducing underwater radiated noise (URN) from vessels and exploring potential co-benefits. The increase of underwater noise from vessels on the maritime environment is well documented in scientific and policy publications. In 2020, through the NDAA, The META Program received direction to begin to look at technical solutions to address noise from shipping and its associated impacts. Initial language provided the opportunity to identify, study, evaluate, test, demonstrate or improve emerging marine technologies and practices to improve reducing propeller cavitation. The 2023 NDAA expanded on this authority to broaden the programmatic focus beyond propeller cavitation to encompass incidental vessel generated underwater noise. This expanded authority will facilitate the exploration not only of technologies and operations that can reduce URN, but also research and demonstrate opportunities that can further elaborate on the linkages between reducing underwater noise and the implementation of decarbonization strategies such as alternative fuels, new vessel designs, and emerging energy and propulsion technologies.
Additionally, the Office of Environment and Innovation is actively engaged in ongoing conversations in the international community linking URN. The International Maritime Organization (IMO) updated the guidelines for URN in July 2023, including an identification of strategies to improve noise reduction efforts that are tied with those to reduce greenhouse gas (GHG) emissions and hosted a workshop identifying such technologies and approaches as well as next steps for research and development in the space.
Completed
Vessel-Generated Underwater Radiated Noise Comparison Study
MARAD partnered with Noise Control Engineering to measure, assess, and contribute to understanding the underwater radiated noise from three tugs, one battery-electric system and two diesel engines. The goal was to compare the underwater radiated noise (URN) generated by the vessels and identify potential noise reductions that can be linked to vessel designs with reduced greenhouse gas emissions. The primary design advantage of the battery-electric system for underwater noise and greenhouse gas emissions is the use of battery power instead of diesel engines. At all transit speeds, the battery-electric system overall URN level is at least 6dB lower than the diesel powered vessels at comparable speeds. However, during simulated tug assist (STA) operations, the noise level is similar or louder than other vessels. Findings from this study may be applied to future vessels to help reduce acoustic impacts on marine life and reduce greenhouse gas emissions. The study is available here.
Current
Testing a novel strategy for ship source level measurement in shallow water - University of North Carolina - Wilmington
(Estimated Completion Q1 2025)
The project consists of three tasks and final report:
- Task 1 will characterize sounds propagation in shallow (<25m) coastal waters by deploying a controlled sound source and a low-cost, horizontal, passive acoustic array perpendicular to the entrance of the Cape Fear River shipping channel in southeastern North Carolina. This task will assist in understanding propagation loss in this environment taking into consideration the depth, bathymetry, and seabed geo-acoustic properties. This is a necessary first step in measuring URN of commercial vessels in shallow water.
- Task 2 will investigate biological sound levels at this coastal ocean location and is necessary to the proposed study because measuring ship noise requires a firm understanding of background noise levels, which include other biological, physical, and anthropogenic sounds beyond the vessel of interest.
- Task 3 will then use the information obtained during Tasks 1 and 2 to measure URN of passing ships along the inbound shipping channel at this location using a vessel tracking approach as suggested by Southall et al. (2017). For Task 3, we will use the Automatic Information System (AIS) to identify the passage of commercial vessels and describe their acoustic characteristics using data collected by the horizontal, passive acoustic array.
Casco Bay Ferry URN Measurement
(Estimated Completion Q1 2025)
The objective of the study is to compare the underwater noise generated by the two ferries: an existing ferry with conventional diesel-geared propulsion and a new vessel with battery electric propulsion. These vessels are to be measured while the vessels are in service with equivalent operating conditions to allow direct comparisons of URN from the vessels. The data collected in this study will be compared with pertinent commercial standards and will be used to identify noise reductions that may be expected on future vessels when a battery electric propulsion system is used. The study will contribute to broader international discussions regarding vessel URN and inform vessel owners and operators of any potential noise reductions that could be realized through changes to existing or new build engines and/or power sources.
Crowley Tug URN Measurement
(Estimated Completion Q1 2025)
The objective of the study will be to compare URN emissions from a tug currently operating with diesel propulsion versus a new-build, replacement e-tug operating on battery electric propulsion in the same environmental conditions (route, season, purpose.) The study must measure the underwater sound pressure level of the vessels over several passes while engaged in varying operations in close-proximity to an underwater listening station(s) and using onboard noise sensors. In addition, the study should make use of and show alignment with, as appropriate, existing international standards and guidelines, class society notations, and/or indicators for measuring vessel URN. The study will contribute to broader international discussions regarding vessel URN and inform vessel owners and operators of any potential noise reductions that could be realized through changes to existing or new build engines and/or power sources.
Modeling Energy, Noise, and Emissions from Vessels
(Estimated Completion Q3 2025)
The Volpe National Transportation Systems Center (Volpe) will support the US Department of Transportation Maritime Administration (MARAD) Office of Environment and Innovation by providing technical support for a model of energy and fuel use, emissions, and noise resulting from maritime vessel traffic in the United States. This work will support MARAD's strategies to facilitate the decarbonization of the maritime transportation sector. The model will be used to quantify and map greenhouse gas (GHG) and criteria pollutant emissions from maritime transportation in the US. In addition, this work will investigate underwater noise sources from maritime transportation.
Last updated: Tuesday, November 19, 2024