Acoustic bandgap characteristics of a duct with a cavity-backed and strip mass-attached membrane array mounted periodically

In this paper, acoustic bandgap analysis of a duct with a cavity-backed and strip mass-attached membrane (CMM) array periodically mounted on its sidewalls is investigated. An analytical model for the bandgap prediction of such periodic vibro-acoustic coupling system has been established via the energy principle in conjunction with transfer matrix method. Results indicate that the proposed CMM resonator can provide a total noise reflection in some frequency and periodic CMM resonators can give rise to attractive Bragg bandgaps. The location and width of the Bragg- and the resonant-gaps can be effectively and expediently adjusted by changing the mass position. Multiple CMM resonators with artificial imperfection via changing the mass position and weight can further strengthen the attenuation effects. The transmission loss spectrum is stretched by several remarkable peaks corresponding to the resonant frequencies of these resonators. It can be concluded that the attached mass can provide an effective and convenient means to enhance and adjust the noise absorption bandwidth of such periodic structure in low frequency. (paper)