Sound Insulation Performance of Composite Double Sandwich Panels with Periodic Arrays of Shunted Piezoelectric Patches

The existing sandwich structure of the aircraft cabin demonstrates a good sound insulation effect in medium and high frequency bands, but poor in the low frequency band. Therefore, we propose an infinite new lightweight broadband noise control structure and study its sound transmission loss (STL). The structure is an orthogonally rib-stiffened honeycomb double sandwich structure with periodic arrays of shunted piezoelectric patches, and demonstrates lighter mass and better strength than the existing sandwich structure. The structure is equivalent according to Hoff’s equal stiffness theory and the effective medium (EM) method. Using the virtual work principle for a periodic element, two infinite sets of coupled equations are obtained. They are solved by truncating them in a finite range until the solution converges. The correctness and validity of the model are verified by using simulation results and theoretical predictions. Eventually, a further study is performed on the factors influencing the STL. All the results demonstrate that the STL in low-frequency can be improved by the structure, and the sound insulation bandwidth is significantly broadened by adding shunted piezoelectric patches. The structure can provide a new idea for the design of broadband sound insulation.

Parametric Analysis of Linear Periodic Arrays Generating Flat-Top Beams

Several synthesis techniques are available to optimize amplitude and phase excitations of periodic linear arrays to generate flat-top beams. Clearly, the optimal tapering depends on design parameters such as the array length, the number of array elements, the beam flatness, the beam width, the side lobe levels, and others. In this paper, in order to derive useful guidelines and rule of thumb for the synthesis of periodic array antennas, relations between these parameters are derived employing linear programming techniques, which guarantee optimality of the solutions. Such relations are then plotted and used in some design examples.