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

Nonuniform deflection of a pressure condenser microphone membrane causes nonlinearities of a relationship between peak deflection of the membrane and the induced voltage. This paper describes how the numerical analysis carried out with the finite element method can help in more accurate determination of this nonlinearity. The dependence of the inverse capacitance (proportional to the induced voltage) on the deflection can be well approximated with the third-order polynomial and the electric field force with the second-order polynomial. There is a major influence of the nonlinearity of the inverse capacitance compared to the nonlinearity of the overall force on the microphone's overall nonlinearity. The deflection profile of the analyzed microphone's membrane is deduced from the values for a 1" microphone.