Improving sound absorption properties of microslit absorbers with flexible tube bundles

Perforated and microperforated panels have been widely used in sound absorption applications. Recently, a perforated panel resonator with flexible tube bundles and double-leaf microperforated panels have been explored to broaden the absorption frequency range, respectively. To take advantages of both methods, a new type of sound absorber is proposed in this paper for better absorption characteristics. The developed sound absorber has a double-layer structure, which is composed of a microslit absorber incorporated as the first layer and a perforated panel resonator with flexible tube bundles embedded as the second layer. The absorption characteristics of the single-layer and double-layer sound absorbing structures with same cavity depths are measured in a standing wave tube. Experimental results demonstrate that the presented absorber provides more effective sound absorption than conventional single layer perforated panel resonator with flexible tube bundles and microslit absorbers in terms of the absorption coefficient and frequency bandwidth, and the perforated panel resonator with flexible tube bundles can be used with traditional resonators in expectation of increasing the sound absorption at lower and median frequencies.