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Ref.: SiPLAB Report 05/07, FCT, University of Algarve,2007.
Abstract
The project Underwater Acoustic Barriers (UAB) started in 2006 with the objective of
proving the concept of using underwater sound propagation to detect submerged objects
crossing a given area. The UAB project involved three phases: i) a theoretical study,
ii) a system development and iii) at sea testing. The first two phases are covered in
current and future publications while this report concentrates on
the testing at sea. The experimental testing of the UAB concept involves establishing
an acoustic propagation plane (barrier) normally in a relatively shallow area (20-30 m
depth) of a bay or port, while the equipment itself is connected to the nearby shore. For
the purpose of this first testing it is important to perform the experiment in a relatively
quiet and environmentally well controlled area, in order to avoid interfering noises and
rapidly changing environmental conditions. These conditions are relatively difficult to
find in Portugal with its long open ocean coast and too shallow semi-enclosed bays or
river estuaries therefore decision was made to apply for performing this experiment at the
Trondheim Research Infrastructure Facility (Hydralab III). The experiment took place at
two different sites: the Trondheimsfjord / Trondheim Biological Station (TBS) using the
R/V Gunnerus and at the Sletvik Field Station (Hopavagen bay) in the periods September
3 - 7 and 8 - 14, respectively. This part A of the report describes the data set acquired
at the bay of Hopavagen during which both the acoustic source array and the receiving
array were moored at an approximate range of 100 m, creating a virtual acoustic barrier.