Coherent Perfect Absorption induced by the nonlinearity of a Helmholtz resonator

TL;DR

This paper demonstrates that nonlinear responses of a Helmholtz resonator can induce coherent perfect absorption of high amplitude acoustic waves, with potential applications in sound attenuation for aero-engines.

Contribution

It introduces an analytical model showing how nonlinear effects in a Helmholtz resonator enable perfect absorption of symmetric incident waves, verified experimentally.

Findings

Achieved perfect absorption of symmetric waves at high amplitudes.

Experimental verification aligns with the nonlinear impedance model.

Potential for designing high amplitude sound attenuators for aero-engines.

Abstract

In this work, we analytically report Coherent Perfect Absorption induced by the acoustic nonlinear response of a Helmholtz Resonator side loaded to a waveguide. In particular, we show that this two-port acoustic system can perfectly absorb two high amplitude symmetric incident waves when the additive nonlinear losses in the HR, induced by the jet flow separation, together with the weak linear viscothermal losses of the HR balance the radiation losses to the waveguide. For the case of the one-sided incidence configuration, this condition leads to an absorption equal to 0.5. This result, which is verified experimentally, is in a good agreement with an analytical nonlinear model of the impedance of the HR. The nonlinear control of perfect absorption using resonators will open new possibilities in the design of high amplitude sound attenuators for aero-engine applications.