Novel study of acoustic window for sonar dome based on resonance-caused sound transmission

The performance of acoustic window of sonar dome is an important parameter to achieve reliable sound detection for ships. Aimed at the low noise and high transmission coefficient designing of sonar dome in ships, a series of acoustic windows of different structures and materials have been carried out so far. Poor suppression performance of flow noise will occur at high speed with a single layer window,which may leads to failure of acoustic window. In order to improve transmission coefficient and reduce flow noise, a novel design of acoustic window has been proposed, of which structure is a rib-stiffened double layer. A series of models of different dimension including layer thickness, rib thickness, rib number, gap thickness are created. Then, the numerical calculation of sound field and flow field is carried out, which uses a combination of finite element method and boundary element method. After calculation, the mean square sound pressure can be obtained. In order to optimize transmission performance of the acoustic window and further reduce the flow noise, 20 different structures of acoustic window are investigated. The velocity of flow is 3,6,9m/s, respectively. The material is steel and the band range is from 1kHz to 8kHz. The performance of hydrodynamic noise are calculated. The result shows that high transmission coefficient can be performed by the resonance produced by coupling of the fluid layer and structure. Meanwhile, fluid noise can be suppressed through the strengthening via the ribs. Numerical simulation indicates that the maximum noise reduction of the novel one is 20dB greater than that of a single layer, ensuring that sound transmission coefficient is not reduced at the same time. It is believed that the results in the paper can provide some reference for the design of acoustic window of sonar dome in the future.