A Systematic Impedance Model for Non-Linear Helmholtz Resonator Liner

The usual non-linear corrections for a Helmholtz resonator type impedance do not seem to be based on a systematic asymptotic solution of the pertaining equations. We aim to present a systematic derivation of a solution of the non-linear Helmholtz resonator equation, in order to obtain analytically expressions for impedances close to resonance, while including non-linear effects. The amplitude regime considered is such that when we stay away from the resonance condition, the non-linear terms are relatively small and the solution obtained is of the linear equation (formed after neglecting the non-linear terms). Close to the resonance frequency, the non-linear terms can no longer be neglected and algebraic equations are obtained that describe the corresponding non-linear impedance. I