Research on the Sound Absorption Performance of Three Dimensional Hilbert Fractal Acoustic Metamaterials

To verify the feasibility of applying the Hilbert fractal curve to the design of three-dimensional sound-absorbing structures, a design and fabrication process for a three-dimensional Hilbert fractal acoustic metamaterial structure (dimensional hilbert fractal acoustic metamaterials, DHFAM) was proposed. The DHFAM structure is made of a resin shell, folded into a maze-like channel with a rectangular tube opening. A simulation analysis was carried out on the influencing factors of the sound absorption coefficient of DHFAM at different orders. The actual data confirm the effects of channel width, channel spacing, and crystal edge length on the sound absorption coefficient. Compared with a single structure, the multi-unit parallel structure expanded the sound absorption bandwidth. Various DHFAM samples were prepared, and the sound absorption coefficients of single DHFAM samples as well as parallel multiple units with different geometric parameters were tested using an impedance tube system. The experimental tests agreed with the simulation results, confirming the successful design and preparation of the metamaterials as described in the text, as well as verifying the multi-unit coupling effect. The study also found that DHFAM exhibits multiple sound absorption peaks in the low-frequency range with high peaks, providing an efficient path for the design of sound-absorbing structures with potential application prospects.