Lu Y., Tang H., Tian J., Li H.

A new type resonant absorber, i.e. the micro-slotted resonator with flexible tube bundle, is presented in this paper. The sound absorbing structure consists of a micro-slotted facing plate and a back sheet as well as the flexible rubber tube bundle. Each flexible rubber tube connects to a hole of the facing sheet via a small connecting tube. The flexible tube length may be much greater than the cavity depth, and can be deliberately made different from one another to absorb sound at different frequencies of interest. Due to the incorporation of the tube bundle into the micro-slotted resonant absorber, not only the absorption coefficients can be increased considerably, but also the frequency bandwidth of absorption can be broadened accordingly. In addition, because of the tube-cavity coupling resonances, through properly design, two or more obviously resonant absorption peaks may occur in the frequency spectrum of sound absorption. The sound absorption properties of the resonant absorber with tube bundle are measured in an impedance tube. The effects of the structural parameters of the micro-slotted resonator with flexible tube bundle on sound absorption are also measured and analyzed. Furthermore, the sound absorption principles of the absorber are also revealed in this paper.