Basic theory about calculating acoustic field distribution was studied using FEM plus IEM.FEM-IEM model was established for the plane nine elements array;directivity and beam width of the array were calculated at three resonance frequencies based on the boundary condition.The varying laws of directivity and beam width were analyzed with frequencies.A broadband plane nine elements array was developed applying triply resonant transducers;the directivity and beam width were measured in anechoic water tank.The ...