The purpose of this PhD project is to develop a complete numerical model for condenser microphones. The measurement principle of these devices is based on the electrical variations in the capacitor formed by a diaphragm exposed to the sound field and a plate inside the body of the microphone. The distance between diaphragm and backplate is of the order of 20 micrometres, giving rise to numerical and physical difficulties in the modelling. First, the very small ratio of gap width to diaphragm dimensions generates instability in the calculations. This problem has been addressed and solved. Secondly, the air trapped inside the gap presents important viscous and thermal losses that must be considered in the model, especially at high frequencies. The Navier-Stokes equations describing the phenomenon are far more complicated than the lossless wave equation. In order to build the model, these equations have been studied and adapted for numerical implementation. A model with thermal losses has been produced and found to give results in good agreement with results from the literature.
|Effective start/end date||01/09/1998 → …|
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