The impact of flow noise on towed and hull mounted acoustical sensors : an introductory study

In this introductory study we have assessed the impact of turbulence generated wall-pressure fluctuations on surfacemounted acoustical sensors, with a special focus on towed sonar arrays. The main findings are that the sound-pressurelevels generally can be expected to be broad banded and exhibit very high SPLs, even at low towing speeds. The SPLs increases dramatically with increased towing speed. By increased the sensor area, the pressure-fluctuations on the surface are convolved such that the SPL decreases. Some brief discussions on transfers of waves within towed antennas are also included, together with some comments on the downstream evolution of a submarine wake and its interaction with a towed antenna. The results of this study show that turbulence generated flow noise on towed, or hull-mounted, acoustical sensors are significant. It is therefore seems necessary to further address this problem in order to understand how flow noise affects these systems which necessarily has an adverse impact on the performance. Such a fundamental study would enable advanced signal processing routines to be tested and further developed, parametric studies concerning optimal design to be conducted as so forth.