Sensitivity of LYBINs transmission loss due to variations in sound speed

This study is motivated by the Sea Acceptance Test 2 (SAT2) to be made sometime in 2006. The testing of the new Norwegian Frigates sonar system will involve use of the acoustic ray trace model, LYBIN. The study reveals that LYBIN is sensitive to certain types of errors in the sound speed, depending on the depth of the sonar. The modelling of the hull-mounted Spherion sonar is sensitive to changes in the surface sound speed, while the variable-depth CAPTAS sonar is more sensitive to sound speed changes at and close to the sonar depth. Suggested procedures regarding monitoring of the sound speed and the depth of the variable-depth sonar during the SAT2-tests are made.