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

A new acoustic liner with controllable impedance based on vortex sound theory was introduced. The impedance of the liner can be controlled according to external sound condition so that the sound absorption coefficient of the liner can keep optimal or constant to satisfy the required impedance condition under any sound source condition value. A set of active control system was designed for this liner. This kind of liner with controllable impedance would be more valuable for active control of engine noise and advanced casing treatment of compressor.