Acoustic liners are used to absorb sound in many engineering, but particularly in aero-engines [1,2].As aero-engines have become progressively larger in diameter, with the introduction of higher bypass-ratio flows, fan noise has become a prominent noise source. The accompanying reduction in jet noise has also unmasked combustion and turbine noise as significant noise sources. This has resulted in their already extensive, and ever increasing.Use in aero-engines to treat fan, combustion and turbine noise.