Characteristic Modeling And Simulation Study On Active Control Of Sound Radiation From Flexible Panel Backed By Acoustical Cavity

The flexible panel is reasonable representation of many engineering occasions, such as the shipbuilding, aerospace, architectural engineering and other fields. The sound radiated by the flexible panel under external excitation is considered as the main noise source. Active noise control shows the satisfied effect of the attenuation for the low frequency sound radiation. In some circumstance, the panel is backed by acoustical cavity, and the radiation from flexible panel backed by acoustical cavity should be taken into account. It can be found that most of the current studies are limited to the sound radiation from single plate structure, and the optimal design for the active noise control is limited. Surrounding the structural-acoustic system, sound radiation and its modeling problem of active noise control, the following research work has been carried out in this thesis:Firstly, the natural vibration and sound radiation characteristics of the plate are investigated with elastic boundary condition. The displacement of the plate is constructed in the form of standard two-dimensional improved Fourier cosine series, and the unknown expansion coefficients are determined using the energy method and Rayleigh-Ritz procedure, the plate sound radiated power and radiation resistance subsequently determined from the near-field Rayleigh integral with the known vibration velocity distribution of the plate. The accuracy and effectiveness of proposed method are demonstrated through numerical examples.The interaction between the structural vibration and sound field is established through increasing the Lagrangian procedure of the sound cavity, which includes the sound pressure acting on the structural-acoustic interface. Some simulation is performed through MATLAB programming language. In the meanwhile, some relevant experimental setups are designed and built up to validate the accuracy of proposed method.The sound power radiated from a rectangular plate backed by cavity is determined from the vibro-acoustic governing matrix equation and the vibration coupling coefficient vector. Some comparisons are presented to show the difference between the coupling and uncoupling circumstances. The effect of the cavity depth and the boundary restraining stiffness on the radiation behavior of planar sources is also studied.Finally,the sound power radiated is chosen as the performance function using the linear quadratic optimal control theory to search for the optimal secondary force. The active structure acoustic control system model is established, and the effect of boundary restraining stiffness, cavity depth, the secondary force position and the excitation source position on the sound attenuation of the controlling system are investigated in much details.