The Theoretical And Experimental Research On Underwater Sound Insulation Performance In Low-Frequency

In order to measure sound insulation performance of two kinds of samples under different water pressure, a high-pressure cylinderical water-tank and a sound field scanning measurement system are designed and developed, by which an experimental research of sound insulation of the samples is carried out.The vibration and acoustic characteristics of the cylinderical water-tank structure with a semi-spherical end have been analyzed by FEM, and the frequency range of the analysis is from 100Hz to 2000Hz. Two types of sound source, the pulsating sphere and dipole source, are adopted to study the variation of the sample's sound insulation in different sound field. Based on the numerical analyses, the cylinderical water-tank, which can undergo high pressure, and a sound intensity scanning device with high scanning precision are designed.The sound insulation characteristic of two samples with different distribution densities and patterns set on the supporting plate are measured in the cylinderical water-tank, and the insertion loss of radiation sound power underwater is calculated and analyzed. During the experiment, both near- and far-field have been measured by a double-hydrophone sound intensity probe array and a vertical single-hydrophone array respectively.The measured sound pressure data in near field has been analyzed by cross-spectrum method for calculating sound intensity and approximation method; and that in the far-field is assumed to be plane wave field approximately. By these methods, the sound intensity distribution on the measuring surface and the radiated sound power have been calculated, and then, sound power insertion loss has been analyzed.The study shows that finite-element method is applicable for researching the sound insulation of underwater complex structures. The experimental measurement system designed in this paper has been successfully applied to the underwater sound insulation test with variable pressure in low-frequency. The sound insulation characteristics of samples is not only related to single sample's construction and performance but also to the sample layout. So, a better sound insulation effect can be expected if the samples are optimized for their layout on the supporting plate.