Sound absorption in Hilbert fractal and coiled acoustic metamaterials

G. Comandini, C. Khodr*, V. P. Ting, M. Azarpeyvand, F. Scarpa

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)


We describe here a class of acoustic metamaterials with fractal Hilbert space-filling and coiled geometry with equal tortuosity for noise mitigation. Experiments are performed using a four-microphone impedance tube and benchmarked against non-viscous and viscothermal finite element models related to configurations spanning up to five fractal/geometry orders. We show that the acoustic absorption can be predicted by the resonance of the cavities associated with the tortuous paths. For a given fractal/geometry order, the acoustic absorption at specific frequencies is also enhanced by maximizing the difference between the minimum and maximum fluid particle velocity of the air inside the patterns. These principles can be used to design high-performance acoustic metamaterials for sound absorption over broad frequency ranges.

Original languageEnglish
Article number061902
JournalApplied Physics Letters
Issue number6
Publication statusPublished - 7 Feb 2022
Externally publishedYes


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