Coiled-up structure with porous material lining for enhanced sound absorption

This paper presents an acoustic metamaterial, coiled-up structure with porous lining (CSPL), which is constructed by adding porous material lining to a coiled-up air channel for the pursuit of broadband and low-frequency sound absorption at subwavelength scales. The porous material is fixed on both sides of the channel wall to enhance the losses of the system, and an air slit is left in the middle of the channel to regulate the impedance matching between the metamaterial and the air. A theoretical model based on double porosity theory and impedance transfer method is established to study the sound absorption performance of the metamaterial, and a finite element (FE) simulation model is constructed to reveal the underlying sound absorption mechanism. To validate these two models, the sound absorption performance of the designed sample is measured in a standing wave tube. The results show that the porous material lining not only enhances the sound energy dissipation, but also reduces the propagation speed of sound wave in the coiled channel, resulting in good low-frequency sound absorption performance of the CSPL. By adjusting the position and length of the porous lining, good sound absorption tunability can be achieved in the considered frequeny range. Moreover, the effect of acoustic properties of the porous material on the sound absorption of the CSPL is revealed and discussed in detail. Finally, several coupled CSPLs are designed to achieve broadband sound absorption in different frequency ranges. This work provides a new approach to design metamaterials for broadband low-frequency sound absorption.

Automated summary

This paper presents a novel acoustic metamaterial called coiled-up structure with porous lining (CSPL), which enhances broadband and low-frequency sound absorption at subwavelength scales. The theoretical model and finite element (FE) simulation model are established to explore the sound absorption performance and mechanism. The results show that the CSPL with porous lining achieves good low-frequency sound absorption due to enhanced sound energy dissipation and reduced sound wave propagation speed. The acoustic properties of the porous material also play an important role in the sound absorption performance.