A compact active structural acoustic control method for minimizing radiated sound power

Active structural acoustic control is an active control method that controls a vibrating structure in a manner that reduces the sound power radiated from the structure. Such methods focus on attenuating some metric that results in attenuated sound power, while not necessarily minimizing the structural vibration. The work reported here outlines the weighted sum of spatial gradients (WSSG) control metric as a method to attenuate structural radiation. The WSSG method utilizes a compact error sensor that is able to measure the acceleration and the acceleration gradients at the sensor location. These vibration signals are combined into the WSSG metric in a manner that is closely related to the radiated sound power, such that minimizing the WSSG also results in a minimization of the sound power. The connection between WSSG and acoustic radiation modes will be highlighted. Computational and experimental results for both flat plates and cylindrical shells will be presented, indicating that the WSSG method can achieve near optimal attenuation of the radiated sound power with a minimum number of sensors.

Investigation of Low-Frequency Sound Radiation Characteristics and Active Control Mechanism of a Finite Cylindrical Shell

In this paper, the radiation characteristics and active structural acoustic control of a submerged cylindrical shell at low frequencies are investigated. First, the coupled vibro-acoustic equations for a submerged finite cylindrical shell are solved by a modal decomposition method, and the radiation impedance is obtained by the fast Fourier transform. The modal shapes of the first ten acoustic radiation modes and the structure-dependent radiation modes are presented. The relationships between the vibration modes and the radiation modes as well as the contributions of the radiation modes to the radiated sound power are given at low frequencies. Finally, active structural acoustic control of a submerged finite cylindrical shell is investigated by considering the fluid-structure coupled interactions. The physical mechanism of the active control is discussed based on the relationship between the vibration and radiation modes. The results showed that, at low frequencies, only the first several radiation modes contributed to the sound power radiated from a submerged finite cylindrical shell excited by a radial point force. By determining the radiation modes that dominate the contribution to the radiated sound, the physical mechanism of the active control is explained, providing a potential tool to allow active control of the vibro-acoustic responses of submerged structures more effectively.

Simultaneous optimization of control parameters and placements of piezoelectric patches for active structural acoustic control of shell structures under random excitation

Simultaneous optimization of multiple parameters of an active structural acoustic control system under random force excitation is presented in this article. A method integrating the pseudo excitation method, finite element method, and boundary element method is proposed to analyze the random acoustic radiation. The active structural acoustic control of randomly vibrating structures is developed using the velocity feedback control scheme with the help of the pseudo excitation method. The acoustic design optimization model is proposed, in which the auto power spectral density of sound pressure is taken as the objective function and the placements of actuators/sensors as well as control gains are assigned as design variables. Taking into account the operational efficiency and control cost, the number of actuators/sensors and the total actuation energy are considered as constraints. A simulated annealing algorithm is employed for the optimization problem with discrete and continuous variables coexisting. Numerical examples are given to demonstrate the effectiveness of the proposed methods and the programs, and several key factors on the optimized designs are also discussed.