Advanced Simulation of a Condenser Microphone Capsule
An advanced numerical model of a pressure condenser microphone capsule is presented. The acoustic space is divided into internal and external domains, with both domains dynamically coupled to the condenser diaphragm motion. The external acoustic domain is modeled using the boundary-element (BE) method, which allows the capsule surface to take an arbitrary geometry. The internal acoustic domain (both the viscous air film and the back chamber) is modeled as coupled cylindrical cavities with negligible axial pressure variation. The diaphragm is modeled as a circular tensioned membrane with negligible bending stiffness. Flow through the back plate is modeled by annular arrays of circular pores with generalized functions locating each pore position. Although the presented model is specialized for a simple pressure condenser microphone, the numerical implementation is sufficiently generic to allow for a large variation in capsule parameters. The complete model is used to generate a simulated response curve, which is compared to a response curve taken from an experimental prototype. The results show excellent agreement throughout the measured frequency range, indicating that this new coupled model may be used for advanced microphone characterization and design.
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