South of São Miguel, in the archipelago of the Azores, three buoys spent 24 hours at sea collecting data – in this case, noise related to human activities that has an impact on the behaviour of cetaceans. For the first time, it was possible to collect information about underwater noise off São Miguel – more than 10 kilometres from the coast; INESC TEC joined this initiative.
“It may not be obvious for a person who dives on a beach, but the ocean is full of sounds, both from biological and human sources, which far exceed our hearing capacity,” said Nuno Cruz, researcher at INESC TEC; the researcher stated that the team was able to collect information about underwater noise and emphasised the importance of collecting this type of data.
CIBIO and IS2E LIACC (University of the Azores), INESC TEC and Whale Watching Futurismo Azores Adventures got together for the second edition of the workshop WAVES – Workshop on Advanced Vehicles for Exploration of the Seas. “In addition to encourage discussions and showcase technologies, we also decided to plan a scientific experiment that would achieve concrete results. Among several hypotheses, we planned this monitoring of acoustic noise,” said Nuno Cruz. The researcher also explained that this is a “particularly relevant activity in the Azores, given the socioeconomic importance of maritime-tourist activities, which also aim to become more sustainable” – and the impact they can have on the behaviour of cetaceans.
In this sense, the researchers equipped three buoys with sound recorders and GPS receivers, which allowed an acoustic recording distributed at various points and with synchronised data. This configuration allowed not only the detection of specific sounds, but also to estimate the location of the sound sources. “Acoustic emission and detection are vital to underwater robotics, since without GPS signals, it is the only viable technology to accurately calculate the position of submerged devices. INESC TEC develops both acoustic receivers and emitters, which are adapted to the operating conditions,” explained Nuno Cruz, recalling the use of similar systems in other contexts – as was the case of the acoustic triangulation system used to locate divers in Brazil.
This experiment introduced a “great challenge”: the location of the study area – more than 10 kilometres from the coast – and the depth of the operation zone. The buoys departed from a considerable distance and, thanks to the currents, could have travelled an even greater distance and be difficult to recover. In addition, there was also a risk of losing communication with them.
“Normally, these buoys are anchored on the coast, where the depth is a few dozen meters, or they are adrift for a few hours, close to us. In this case, the study area was located several miles from the coast, with a depth of many hundreds of meters, so it would be very difficult to anchor them. In addition, the data collection process was going to last 24 hours. We had a currents’ forecast, but during this period, the currents could’ve taken them very far, making it harder to recover the buoys. Moreover, if we lost communications, even with a fast vessel, we knew we were more than an hour away, so constant monitoring of position and speed was important.”
According to the INESC TEC researcher, the joint effort of several entities was fundamental for the success of the experiment: the Port Authority of Ponta Delgada – which provided drift models to estimate the course of the buoys; the company Whale Watching Futurismo, and the marine biology team – namely biologists Laura García and Margarida Rolim, who carry out cetacean monitoring -, which led the study and provided a vessel and lookouts along the coast to confirm cetacean sightings; and a team to monitor the position of the three buoys during the 24-hour period. “Everything went according to plan. The buoys were deployed on the morning of November 17, and collected on the following day, having acquired about 40 GB of information, over several tens of kilometres” – data whose preliminary analysis has already allowed the discussion of new monitoring activities, as well as the planning of new project proposals.
In addition to participating in this noise monitoring experiment, the INESC TEC team also carried out a demonstration of the MARES Autonomous Underwater Vehicle – studying how this type of vehicle can be used to monitor underwater structures in ports, e.g., to detect faults and other disturbances. “We also discussed the organisation of the WAVES 2025 edition!” concluded Nuno Cruz.
The researcher mentioned in this news piece is associated with INESC TEC and UP-FEUP.
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