The design and experimental investigation of control system for acoustic liner with controllable impedance

In this study,a kind of new acoustic liner with controllable impedance based on vortex sound theory has been introduced.The impedance of this kind of liner can be controlled according to external sound source condition so that the sound absorption coefficient of the liner can keep optimal or the liner can satisfy requested impedance condition under any sound source condition.A set of active control system has been designed for this kind of liner in this investigation.The quality of this kind of liner with control system has been improved greatly.Especially with the appearance of concept about active control of unsteady flow of the compressor,it will be found that this kind of liner with controllable impedance would be more valuable for active control of engine noise and advanced casing treatment of compressor.