A microacoustic analysis including viscosity and thermal conductivity to model the effect of the protective cap on the acoustic response of a MEMS microphone.
A microacoustic analysis including viscosity and thermal conductivity to model the effect of the protective cap on the acoustic response of a MEMS microphone.
复制标题
微声学分析（包括粘度和导热系数），用于模拟保护盖对 MEMS 麦克风声学响应的影响。
DOI：
10.1007/s00542-013-1800-5
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
Zuckerwar,AJ
中科院分区：
文献类型：
--
作者：
Homentcovschi,D;Miles,RN;Loeppert,PV;Zuckerwar,AJ
分析了保护罩对微型硅传声器声响应的影响。麦克风膜片被包含在一个小的矩形外壳内，声音通过外壳顶部表面的一个小孔进入。提出了声场随位置变化的数值模型。本研究的目的是确定压力分布在哪个频率下保持足够均匀，以便在自由空间中进行压力校准。这项工作的第二个动机是通过提供一种方法来预测麦克风振膜在封装中的位置如何影响灵敏度和频率响应，从而促进麦克风设计。虽然封装的尺寸相对于感兴趣的声音的波长通常很小，但由于封装的尺寸与粘性边界层的厚度相同，因此粘度会显著影响膜片周围声压的分布。除了需要考虑粘性效应外，这里还表明，人们还必须仔细考虑导热性，以适当地表示系统主声共振频率下的能量耗散。用有限元法求解由连续性方程、Navier-Stokes方程、状态方程和能量方程组成的线性化系统的声场。在可听频率范围内，声压的振幅和相位的预测空间变化被显示出来。封装对麦克风灵敏度的预测和测量结果非常吻合。
An analysis is presented of the effect of the protective cover on the acoustic response of a miniature silicon microphone. The microphone diaphragm is contained within a small rectangular enclosure and the sound enters through a small hole in the enclosure’s top surface. A numerical model is presented to predict the variation in the sound field with position within the enclosure. An objective of this study is to determine up to which frequency the pressure distribution remains sufficiently uniform so that a pressure calibration can be made in free space. The secondary motivation for this effort is to facilitate microphone design by providing a means of predicting how the placement of the microphone diaphragm in the package affects the sensitivity and frequency response. While the size of the package is typically small relative to the wavelength of the sounds of interest, because the dimensions of the package are on the order of the thickness of the viscous boundary layer, viscosity can significantly affect the distribution of sound pressure around the diaphragm. In addition to the need to consider viscous effects, it is shown here that one must also carefully account for thermal conductivity to properly represent energy dissipation at the system’s primary acoustic resonance frequency. The sound field is calculated using a solution of the linearized system consisting of continuity equation, Navier–Stokes equations, the state equation and the energy equation using a finite element approach. The predicted spatial variation of both the amplitude and phase of the sound pressure is shown over the range of audible frequencies. Excellent agreement is shown between the predicted and measured effects of the package on the microphone’s sensitivity.