Enhancing the sound transmission loss through acoustic double panel using sonic crystal and porous material

Acoustic panels are widely used for sound insulation in various applications. Sound transmission loss (STL) through the panel is due to a change in acoustic impedance as sound travels from one medium to another. In double panels, STL further increases due to multiple reflections in air cavity. Recently the sonic crystal (SC) has emerged as an interesting research topic which provides sound attenuation in specific frequency bands. The present paper aims at combining the property of a SC with the acoustic panel for enhancing the STL through the double panel. Initially, an analytical method is developed to obtain the STL through the double panel. Further finite element (FE) simulations are performed using acoustic structure interaction to obtain the STL through the double panel which is in good agreement with the analytical predictions. The SC, along with the double panel, is analyzed using the FE method for the combined effect of both sound attenuators. Further, glass wool is considered as a filler material between the double panel as well as between the double panel and the SC assembly. It is found that the combined structure of the double panel and the SC with glass wool as filler gives the best STL for all different cases for the same external dimensions.