Sound absorption performance of thin hierarchical honeycomb panel with embedded porous-layer

A novel sound-absorbing structure based on thin hierarchical honeycomb panel with embedded porous-layer (HHPEP) is designed, and an impedence-based analytical model based on the equivalent circuit method is proposed to capture its absorption characteristics accurately. The better sound absorption performance of HHPEP absorbers than that of conventional honeycomb panel absorbers in the low-to-medium frequency is theoretically and numerically verified, and the impact of structure thickness, embedded porous-layer, hierarchical scale ratio, and air temperature on the sound absorption performance of HHPEP absorbers is analyzed. Results show that the HHPEP absorber can achieve quasi-perfect sound absorption in relevant low-to-medium frequency even if its total thickness is only ≤30 mm, while both the conventional honeycomb panel and HHPEP of similar structure thickness demonstrate hardly effective sound absorption. Meanwhile, the smaller hierarchical scale ratio is conducive to enhancing the sound absorption performance of HHPEP absorbers, and the embedded porous-layer with higher static flow resistivity can remarkably improve its sound absorption performance. Overall, the thin HHPEP absorber shows good sound absorption performance in the low-to-medium frequency, which is promising to be used as a hybrid acoustic liner for reducing the low-to-medium frequency noise in aviation, construction, and environmental fields.