Scientifically Speaking — MARS Project
Scientifically speakingThe MARS Project: A gathered team in Quebec in search of precise mitigation actions to reduce underwater noise
Maritime traffic has increased sharply in recent decades. The commercial fleet has gone from about 30,000 vessels after World War II to nearly 100,000 today with the trend accelerating.
The level of noise radiated into the marine environment typically increases in tandem with maritime traffic. It is generally accepted within the scientific community that the acoustic energy radiated by ships on a global scale doubles every decade.
Underwater noise produced by human activities can have negative effects on wildlife, particularly species at risk in Canada (North Atlantic right whales, beluga whales, killer whales and blue whales).
These effects could take the form of altered communications, behavioural disturbances and physiological responses. It is still difficult at present to quantitively translate these effects into ecological impacts on individuals and populations.
In a very proactive approach, Canada has recognized the noise related to maritime traffic as a new type of marine pollution and wishes to decrease these effects in reconciling the essential services of maritime trade in tandem with reducing its negative impacts on wildlife.
A winning approach is to understand the causes of radiated noise on individual vessels and propose methods of reduction on the ship. This is the challenge that the MARS Project is attempting to achieve.
The MARS Project is divided into four main components:
The first consists of setting up and operating an underwater acoustic research station (4 antenna-equipped buoys, 12 hydrophones) of international standards in the St. Lawrence Estuary.
The station conceived, manufactured and operated by Multiélectronique (MTE) and OpDAQ Systems is currently the only fixed platform, operating 24/7 and globally connected to comply with the ANSI/ASA S12.64 2009 standards to measure the underwater noise generated by a vessel.
Located by the St. Lawrence navigation channels, it facilitates ships measuring their noise without having to divert off course and lose time (see figure 1). The MARS station makes it possible to relate precise information on the noise radiated by each vessel passing through the station to establish its acoustic signature. ISMER-UQAR is responsible for this second component.
The project’s third component, carried out by Innovation Maritime (IMAR), involves taking noise and vibration measurements aboard vessels while they pass through the station. These measurements facilitate characterizing and ranking the sources of ship noise.
With the combination of data taken aboard the vessels and by the station it becomes possible to link the most problematic levels of noise to their sources on or within the ships. As a result, it is easier to make a clear diagnosis and suggest noise-mitigation actions that are tailored to each ship (the project’s fourth component). This makes it possible to adopt a pragmatic approach to the proposed noise reduction solutions and maximize their environmental impact.
The MARS station was initially deployed in the Summer of 2021. Thirty-eight (38) acoustic signatures were recorded and analyzed by ISMER.
At the same time, the first shipboard diagnostic mission was carried out aboard the Bella Desgagnés as it passed through the station.
The station, which has to be put into winter hiatus, is back in service from May to October 2022. As a result of this longer duration of operation and the acquired experience, 150 signature measures and four to seven diagnostic missions are expected for the 2022 year.
The project’s next stage is to propose to ship owners some ways to achieve noise reduction after quantifying their acoustic decrease in relation to the cost and difficulty of implementation so as to come up with acceptable, effective environmental solutions. The two primary sources of noise on vessels are the machinery and propellers. Propeller-related noise control must be considered right from the ship’s design phases, so efforts are currently focused on machinery-related noise.
Frequency spectrums
The illustrations below show the frequency spectrums of the radiated noise from two ships that passed through the MARS station. A spectrum is a graphed presentation of all the frequencies contained in that noise. Low frequencies correspond to lower-pitched sounds, while high frequencies correspond to higher-pitched sounds.
In the illustration, the spectrum on the left is characteristic of a vessel whose main source of noise is the propeller. This can be recognized by the more or less smooth rise at low frequency. The spectrum on the right is more characteristic of machinery noise with the narrow peaks, or lines, emerging from the curve. These relate to specific mechanical elements on the ship: gears, ignition in the combustion chamber, RPM, etc. The green lines in the graph fall inside the beluga whale’s communication frequency range (200 – 2000 Hz). By way of example, mitigation of these would reduce the noise radiated by the ship by a factor of 4, doubling the communication radius of beluga whale whistles in this frequency range whose sound could be masked by ship noise.
The team is now working to identify mitigating solutions to offer the partnering ship owners. Some traditional avenues are being considered, such as elastic insulators, studying the impact of speed, and different types of fuel. At the same time, other projects related to MARS are starting up at IMAR to propose more innovative solutions. These measures will be tested in collaboration with the partnering ship owners and then evaluated during subsequent visits to the acoustic station.
Author :
The article was prepared on behalf of the MARS team by Jean-Christophe Gauthier-Marquis, MSc, who is a researcher at Innovation maritime (IMAR).
Along with experience in physical oceanography (sea ice fragmentation and deformation), he is involved in a number of scientific projects at IMAR. He is also a college-level teacher.
The MARS Project:
A gathered team in Quebec in search of precise mitigation actions to reduce underwater noise
The project is co-funded by Transport Canada, the Ministère de l’Économie et de l’Innovation du Québec, and the St. Lawrence Economic Development Council (SODES). Initiated by the l’Institut des sciences de la mer de Rimouski (ISMER-UQAR) and Innovation maritime (IMAR), it also involves two SMEs in Rimouski (MTE Inc., OpDAQ Systèmes Inc). It aims to provide the partnering ship owners (Algoma, Canada Steamship Lines, Desgagnés and Fednav) with essential solid information to take actions regarding the underwater noise generated by their ships.