Numerical determination of electric field forces and capacitance of pressure condenser microphone

Nonuniform deflection of pressure condenser microphone membrane causes nonlinearities between peak deflection of membrane and induced voltage. The microphone\´s capacitance was determined for the first time with finite element method. The dependence of capacitance and inverse capacitance dependence on deflection is fitted by a polynomial. These data are used for determination of static point and electric field force. The dependence of inverse capacitance (proportional to the induced voltage) on deflection can be approximated with a third order polynomial, and electric field force with a second order polynomial. There is a major influence of the nonlinearity of the inverse capacitance (maximal per cent change of the gradient up to 4%) compared to the nonlinearity of the overall force (maximal per cent change of the gradient under 0.15%) on the microphone\´s overall nonlinearity. The geometry of the analyzed microphone is deduced from values for a 1" microphone