Calculation and analysis of low frequency acoustic radiation of two elastically-connected double rigid spheres under axial excitation

It is of great significance to study the vibration and noise reduction method of the multi-cabin structures which are generally adopted by low noise large-deep underwater vehicles. An analytical model of the acoustic field radiated by the axial vibration of two elastically-connected rigid spheres was established in this paper using the translation addition theorem of spherical wave functions. The radiated acoustic field characteristics of different connection cases between the two rigid spheres below 100 Hz were compared, the two rigid spheres could be considered as a rigid body in this low frequency range. The calculation results show that the elastic connection between the spheres can reduce the vibration amplitude of the rigid spheres without external force. Moreover, there are opposite frequency bands between the vibration velocity phases of the two rigid spheres. The phases of sound pressure radiated by different spheres are opposite and the sound pressure of each part can cancel each other. When the radiation intensity magnitude of the two spheres is similar, the sound source level has an obvious low point. For two elastically-connected spheres, the force acting on one sphere with a large equivalent density can bring lower noise than that on the other sphere with a low equivalent density. The results can provide a reference for low noise design of multi-cabin underwater vehicles. © 2022, Editorial Board of Journal of Ship Mechanics. All right reserved.