Experimental and finite element analysis on the sound absorption performance of wedge-like knitted composite

Limited by the single mechanism of sound absorption, most current sound-absorbing materials exhibit difficulties in balancing weight and acoustic performance. In this work, a flexible wedge-like knitted composite (WKC) realized by knitting and coating technology with multiple sound-absorbing mechanisms including porous sound absorption mechanism and wedge-like structure resonant mechanism is proposed. To study the influence mechanisms of coating and wedge structure on the sound absorption performance, experiment and finite element analysis were both conducted. By improving the porosity distribution through the addition of viscoelastic layer, the sound absorption coefficient (SAC) is enhanced by 239%, which is originated from the infiltrated silica gel into the fabric pores, increasing the complexity of the penetration path. The wedge structure plays a necessary role on enhancing the sound absorption coefficient under low frequency because the concave–convex surface of wedge generates stronger resonance of rear air cavity. The size effect of wedge shape is analyzed in terms of acoustic vibration angle and acoustic energy dissipation density. The increase of the acoustic vibration angle increases the reflection collision path and speed of sound vibration, which further enhances the energy dissipation. Therefore, the combination of viscoelastic coating layer and wedge structure effectively promote the sound absorption, especially at low frequency. This work provides guidance for the structural design and realization of innovative flexible sound absorbing materials, which is promising in application prospect of indoor curtain interiors, wall coverings and automotive interiors.