An investigation on the characteristics of a non-locally reacting acoustic liner

Abstract

A finite element acoustic model was proposed for investigating the characteristic of a novel non-locally reacting acoustic liner. This non-locally reacting acoustic liner was based on the so-called multiple cavity resonance mechanism which could broaden the absorption bandwidth. The basic idea of it was that when the back cavity of the liner was partitioned into sub-volumes of different size, multiple resonances relating to different length were produced so that the attenuation peaks came closer and worked jointly to provide high attenuation over a broad frequency band. There were strong coupling effects of the resonances inside the back cavities and in the duct when the sound propagated in the duct installed this non-locally acoustic liner. The proposed finite element acoustic model could simulate the entire sound field both in the duct and inside the back non-uniform cavities of the liner including the strong coupling effects. The comparison between the numerical and the experimental results demonstrated that, the finite element acoustic model was an accurate, stable and rapid method for investigating the acoustic characteristic of this novel non-locally reacting acoustic liner. The numerical study was also targeted for developing an optimal non-locally acoustic liner for engineering applications.