Advanced Simulation of a Condenser Microphone Capsule
An advanced numerical model of a pressure condenser microphone capsule is presented. The model divides the acoustic space into internal and external domains and couples the dynamic pressure in each domain to the capsule diaphragm motion. The external acoustic space is modeled using the boundary element (BE) method which allows for arbitrary geometry of the capsule/microphone external surface. The diaphragm is modeled as a circular tensioned membrane of negligible bending stickiness. The internal acoustic space (both the viscous air film and back chamber) is modeled as a cylindrical cavity with negligible axial pressure variation. Flow through the back plate is modeled as an annular array 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, implemented in a software package called VC, is used to generate a simulated response curve that is compared to a response curve taken from an experimental prototype. The results show excellent agreement throughout the measured frequency range, indicating this new coupled model may be used for advanced microphone characterization and design.
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