Nonlinear acoustic damping induced by a half-wave resonator in an acoustic chamber

Nonlinear acoustic damping induced by a half-wave resonator is investigated numerically by adopting nonlinear analysis. Governing equations describing nonlinear acoustic fields in a chamber are solved simultaneously. The two acoustic properties of damping factor and insertion loss are adopted to quantify acoustic damping capacity of the resonator. As the amplitude of pressure disturbances increases, the baseline damping capacity of the chamber without the resonator increases gradually and then, rapidly. The optimal length found in a linear range is still valid in a nonlinear range. But, pure acoustic-damping effect induced by fine tuning of the resonator is degraded rather by nonlinear acoustics. The effect can be clearly quantified by the insertion loss, not the damping factor. From the acoustic fields in an acoustic tube with a single resonator, the insertion losses are calculated with two adjustable parameters of the resonator length and sound pressure level. It is validated even by the insertion-loss approach that the resonator functions as a half-wave resonator in a linear range. From nonlinear responses of the resonator, it is found that the damping capacity of the resonator is degraded and becomes nearly identical irrespective of the resonator length when high-amplitude acoustic oscillation is excited.