Comments: download file (pdf)
Ref.: SiPLAB Report 05/07, FCT, University of Algarve,2007.
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.