A hybrid active-passive sound absorber

The structure of an active-passive sound absorber is considered, and issues concerning analytic and experimental studies of the efficiency of sound absorber operation are discussed. A description is presented of both the passive part of the hybrid sound absorber and the active system incorporated in it. A test bench constructed on the basis of a low-frequency acoustic interferometer for measuring the sound absorption coefficient and the input impedance of the hybrid sound absorber under normally incident sound waves is described. An algorithm is proposed for controlling the active system of the hybrid sound absorber. The operation efficiency of the active system controlled by the proposed algorithm is analytically investigated. The results obtained from the experimental study of the hybrid active-passive sound absorber on the measuring test bench are presented.