Underwater sound radiation control by active vibration isolation: An experiment

Abstract

An experimental system, mainly including a rotary machine, four active vibration isolators and a water container, was established to investigate the role of active vibration isolation in suppressing vibration transmission as well as underwater sound radiation. Finite element analysis and experimental modal testing were employed to exhibit and validate vibration modes of the fluid-coupled structure and the radiated sound field in water. Sound field given by this validated finite element model is taken as the substitution for a real measurement. In the experiment, the fundamental frequency of the rotary machine was chosen to be nearly equal to a natural frequency of the coupled system in order to create a sound field in the water container by resonant structural vibration. The rotary machine is supported by the four electromagnetic vibration isolators, which suppress the quasi-periodical local vibration independently according to an adaptive control method. The measured results have demonstrated that low-frequency sound radiation can be reduced by local active vibration isolation.