Conference_programme: 7.1 - Advances on numerical methods for computational acoustics

Lecture: Modeling of several measurement condenser microphones using the Boundary Element Method

Author(s): Cutanda Henriquez Vicente, Barrera Figueroa Salvador, Risby Andersen Peter

Summary:
Condenser microphones are reliable and stable devices with outstanding performance. These properties make them suitable for high-end audio applications and acoustic measurements. Their transduction principle relies on the charge variations induced in the capacitor formed by a stretched metallic diaphragm, exposed to the sound field, and a very close back electrode. The thickness of the gap between electrodes is just a few micrometers, and determines not only the sensitivity of the transducer but also the damping, through viscous and thermal losses, of the diaphragm resonance. The device is therefore a strongly coupled combination of the electrical capacitor, interior cavity, gap region, diaphragm and external domain.\nThe creation of models of condenser microphones involves some specific challenges: i) the aspect ratio of the microphone dimensions is very large, so that the model has to deal with a very thin gap and other much larger domains, ii) viscous and thermal losses in the gap are very relevant and need to be modeled accurately, and iii) verification of microphone models is conditioned by the uncertainty of their internal parameters, even among units of the same model.\nIn this work, current work on models of condenser microphones based on a Boundary Element Method formulation with losses is presented. Three-dimensional models of microphones of ¼’’, ½’’ and 1’’ are shown. The larger microphones include holes in the back electrode, with the function of controlling the damping.\nThe work focuses on the challenges involved in the modeling, and how the BEM implementation deals with these difficulties.\n

Corresponding author

Name: Dr Vicente Cutanda Henriquez

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Country: Denmark