Bai Mingsian R, Chen Rong-Liang, Wang Chun-Jen
Department of Mechanical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan.
J Acoust Soc Am. 2009 Jun;125(6):3632-40. doi: 10.1121/1.3117377.
An unconventional type of electrostatic loudspeaker is presented in this paper. The loudspeaker made of thin, light, and flexible electret material lends itself well to the space-concerned applications. Electrical impedance measurement reveals that the coupling between the electrical system and the mechanical system is weak, which renders conventional parameter identification based on electrical impedance measurement impractical. A different approach is thus employed to model the electret loudspeaker. To predict the loudspeaker's dynamic response, finite-element analysis (FEA) is conducted on the basis of a simple model and a full model. In the simple model, FEA is applied to model the electret membrane, leaving the rest of system as rigid parts. In the full model, FEA is applied to model the entire membrane-spacer-back plate assembly. Velocity response of the membrane subject to a uniformly distributed force is calculated using FEA harmonic analysis. Mechanical impedance is then calculated with the velocity response. The acoustical impedance due to the back cavity, pores, and the radiation loading at the front side is calculated by theoretical formulas. The volume velocity of the membrane and the resulting on-axis sound pressure level are predicted with electrical-mechanical-acoustical analogous circuits. The response data predicted by the simulation compare very well with experimental measurements.
本文介绍了一种非常规类型的静电扬声器。这种由薄、轻且柔韧的驻极体材料制成的扬声器非常适合空间受限的应用。电阻抗测量表明，电气系统与机械系统之间的耦合较弱，这使得基于电阻抗测量的传统参数识别方法不切实际。因此采用了一种不同的方法对驻极体扬声器进行建模。为了预测扬声器的动态响应，基于一个简单模型和一个完整模型进行了有限元分析（FEA）。在简单模型中，有限元分析用于对驻极体膜进行建模，而将系统的其余部分视为刚性部件。在完整模型中，有限元分析用于对整个膜 - 间隔物 - 背板组件进行建模。使用有限元谐波分析计算膜在均匀分布力作用下的速度响应。然后根据速度响应计算机械阻抗。通过理论公式计算后腔、孔隙以及前侧辐射负载所产生的声阻抗。利用机电声类比电路预测膜的体积速度和由此产生的轴向声压级。模拟预测的响应数据与实验测量结果非常吻合。
