SEPARATION OF SHIP PROPELLER CAVITATION AND CAVITATION TUNNEL NOISE USING INDEPENDENT COMPONENT ANALYSIS
Endang Widjiati, Eko Budi Djatmiko, Wisnu Wardhana, Wirawan Wirawan · 2014
One of tha main task of a submarine is to detect a surface ship or another submarine, moving in the surrounding field by means of its sonar system. Detection process is done by exploiting acoustic signals emitted by the ship or submarine spotted. Previous literatures confirm that under certain condition, the noise originated by the ship is dominated by its propeller cavitation noise. To be able to characterize the propeller cavitation noise, an experiment is conducted in a Cavitation Tunnel facility belonging to the Indonesia Hydrodynamics Laboratory (IHL) Surabaya, Indonesia. The noise is generated by using B-series four-blade propeller placed at a widow section of the K16B type cavitation tunnel, rotated at varying velocity with water flow of various speeds. The acoustic noise produced, is then recorded through a hydrophone array placed at the top of the measurement section. From this experiment, it is found that the propeller cavitation noise recorded, is mixed with other acoustic interferences originated from other system components of the cavitation tunnel. These acoustic noise interferences,further referred to as the system noise, need to be separated from the recorded signal to get the real propeller cavitation noise. The separation process reported here in is done by applying the Independent Component Analysis (ICA), where the recorded signal is assumed to be a mixture of the propeller cavitation noise and the system noise. ICA is chosen, since it is a computationally efficient blind source separation technique, which can extract individual signal from their mixtures. In order to get a reference of the system noise, another acoustic noise is recorded when no propeller is placed in the tunnel and only the water is flown inside the tunnel. The spectral characteritics of this system noise will be compared with its of the system noise resulting from the separation process.