Tunable network sound absorber based on additive manufacturing

Broadband sound absorption at low frequencies is always a challenge owing to the strong penetrability of acoustic waves. Combining detuned components, such as coupling curled Fabry-Pérot channels, has been proposed for broadband sound absorption. However, the components of the structure are generally arranged in parallel, so that it is difficult to assemble channels with gradient lengths into a compact and thin absorber. Tube networks, which can be seen as broadband and low-frequency sound absorbers, can circumvent this problem. However, the network absorber can only work at fixed frequencies once fabricated. Here, we propose a tunable low-frequency sound absorber consisting of honeycomb plates and detached chips and fabricate it by additive manufacturing. By replacing chips of the sound absorber, we experimentally validate different sound absorption spectrums. A low reduced frequency model and genetic algorithm are developed to design the chips according to targeted absorption spectrums. Moreover, we theoretically study the impact of radius of tube on sound absorption and extend the two-dimensional network to a three-dimensional structure. The remarkable efficiency and versatility of the tunable network sound absorber may pave the way for programmed absorbing material design.