Structural-Acoustic Design of Double Cylindrical Ring Stiffened Shell Based on Line Spectrum Reduction of Radiation Noise

In order to reduce line spectrum of radiation noise from submarine, a type of weak radiation double cylindrical ring stiffened shell was proposed. Mechanical impedance theory was used to analyze mechanism of controlling the modal response amplitude of ring-stiffened cylindrical shell. Radial modal mechanical impedance of the ring was derived by introducing the assumption of inner-motion of cylindrical shell's section. Based on the concepts of impedance mismatch and wave conversion, the model of impedance enhancement rib was built and its isolation performance was analyzed. With the consideration of the brace's strong coupling effect, the brace's wave attenuation was designed. Combining the structures of reinforced impedance rib and wave attenuation brace, the structure-borne sound design of double cylindrical shell was done. Further, the characteristics of vibration and sound radiation were numerical analyzed. The results show that the proposed double cylindrical ring stiffened shell could realize radiation noise line spectrum reduction effectively. The vibration mean square velocity, radiation sound power and sound pressure are depressed greatly. The effect of noise depression and vibration reduction is obvious.