Broadband low-frequency sound absorption of honeycomb sandwich panels with rough embedded necks

A hexagonal honeycomb sandwich panel with rough embedded necks is proposed as a new structure for broadband low-frequency sound absorption. A theoretical model is established to study the sound absorption performance of the structure, and a finite element model is also developed to explore its sound absorption mechanism. The results show that the structure has excellent broadband low-frequency sound absorption performance. The energy dissipation mainly occurs in the neck, and the energy dissipation of the neck can be enhanced by adjusting the relative roughness of the neck. As a result, the sound absorption peak of the structure increases and the peak frequency shifts towards low frequencies. Also, thinner structures will shift the peak frequency to high frequencies. By reasonably adjusting the height of the honeycomb cavity and the relative roughness of the neck, the effects of these two changes can be balanced to achieve the perfect sound absorption of the thinner structure in the low frequency band. Based on the electro-acoustic analogy method, the broadband perfect sound absorption of thin structure in low frequency can be realized by reasonably paralleling different units with rough embedded necks. Experimental measurements are carried out, and favorably verify the theoretical model and the finite element model, as well as the broadband low-frequency design scheme. This work opens up a new way to design thin acoustic metamaterials for broadband low-frequency sound absorption.