Theory and experiments on the coupling of two Helmholtz resonators

The acoustic coupling between closely located acoustic resonators can have a significant effect on the resonance properties. Examples of the influence of coupling include pipe musical instruments such as flue organs or flutes, where the coupling may affect the sound. Here, a physical model of a system of two coupled Helmholtz resonators is developed. The coupling is described by the mutual impedance between the neck openings, and an additive reflection impedance modification to the radiation impedance, which models the effect of reflections from the outer "shell" of the other resonator. The theoretical predictions show a good agreement with measurements also reported here. Finally, the effects of coupling on the present system are analyzed.