Sea Technology

SEP 2018

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Page 23 of 53

22 ST | September 2018 Ice Movement The RTsys EA-SDA14 is highly versatile, so researchers have been able to use the same equipment for recording various noises, even at very low frequencies. They have re- corded noise made by wildlife such as bivalves (including scallops), bearded seals, walruses and minke whales, as well as noise from ice. The first sign of an iceberg break- ing away from a glacier is the noise made by the ice dilating. This can be compared to the cracks that ap- pear on an ice cube in a glass of whiskey. Other noises correspond to blocks breaking off and, lastly, the loud crash made by the ice fall- ing into the water that comes with calving, when the iceberg breaks away from the glacier. Divers com- pare this noise to the grand finale of a fireworks display; they can feel the vibrations inside their chests. A system made up of four syn- chronized hydrophones, which are placed 2 m apart from one another, is used to determine an iceberg's position. The divers have not ex- perienced any difficulty using the EA-SDA14 system, which has four synchronized acquisition channels. The device has opened up new possibilities and created new uses for acoustic recorders. According to researchers, possible uses include monitoring the state of the ice to learn about its position, volume and the time and date at which it breaks away. Chauvaud has been working on such research with glaciologists from Brittany, who now have a tool that meets their needs in remote de- tection work. Researchers are also thinking about the possibility of us- ing the recorders over extended pe- riods of time, for example over 12 months close to the Dumont d'Ur- ville Antarctic Base, which would require very robust and reliable equipment. Unknown Effects of Noise The measurement of noise in the ocean could enable "underwater landscapes" to be mapped that in- clude information on the physical environment and ice, information on underwater life, noise made by wildlife, and anthropogenic distur- bance and its impact. For example, it is not difficult to imagine that the sonar impact of human activity close to the Daneborg Marine Sta- tion in Greenland, where only a few boats a year go by, is very different from the impact off the much more trafficked coast of Brittany. The development of offshore re- newable energy is another source of noise, during construction as well as operation, so studying the effects on marine wildlife is highly relevant. While the impact on ma- rine mammals is relatively well doc- umented, the study of invertebrates is only carried out by three groups of researchers in the world, one of which is Chauvaud's laboratory at BeBEST. Oceanopolis Aquarium Simulations In order to fine tune their study on the impact of differing noise lev- & LINEAR For mor building amplifiers to drive reactive loads. 7263 Engineer Rd., San Diego, CA 92111-1493 (858) 571-1111 FAX (858) 571-0188 Copyright 2018 isit our Model S16-20 A A 20% duty 35 x 31.5 x 35.5 inches; 985 lbs.

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