中文摘要：

指向性是描述声源的一个很重要的声性能参数。边界自由条件下,方形薄板没有位移解析解,加之纵振换能器在激励方形辐射板时与板有一定的接触面积,不能视为点接触,这增加了计算纵振—方形辐射声源指向性的难度。本文基于对瑞利积分公式的离散,结合有限元数值计算方法,计算了不同激励面积下方板的指向性。结果表明：激励面积将影响方板表面节线分布和纵弯系统的共振频率,进而影响辐射声场的指向性。激励面积较小时,声场指向性较差;激励面积不断增大,方板表面节线组成的圆角正方形逐渐减小且系统共振频率增大,声场指向性逐渐尖锐。

英文摘要：

It is an important acoustic parameters that directivity pattern describes the characteristics of radiated acoustic field. Square thin plate with flexural vibration under free boundary conditions have no analytical solutions in addition there have excited area when longitudinal transducer excited square plate,so that it is very hard to calculate directivity pattern. In this paper,we study the directivity pattern of square plate based on discrete Raleigh＇s integral formula and the finite element method. The experiment and analysis show that the excited area will affect the distribution of nodal line and resonance frequency of system which lead to different directivity pattern. When the excited area is larger,the interference cancellation caused by the vibration displacement,which in the opposite direction on the two sides of nodal line will less than the smaller excited area,the directivity pattern is better.