Acoustic transmission loss in Hilbert fractal metamaterials

Comandini, Gianni; Ouisse, Morvan; Ting, Valeska P.; Scarpa, Fabrizio

doi:10.1038/s41598-023-43646-1

Cited by 7 publications

(2 citation statements)

References 60 publications

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“…A plane wave p in = p 0 e iωt with unit amplitude p 0 = 1 Pa is applied at the left entrance of the waveguide. To simulate a metamaterial with infinite size in the y direction, periodic boundary conditions are applied at the upper and lower ends of the first-order, second-order, and third-order units, and the solid wall is set as a hard boundary condition [28,29]. Perfectly matched layers (PML) are set at the front and back ends of the waveguide to eliminate the influence of reflected waves.…”

Section: Calculation Of Effective Parametersmentioning

confidence: 99%

“…To further study the acoustic properties of the designed AAMs, thermoviscous acoustics (ta) were used to calculate the sound transmission loss of the first-order, second-order, and third-order AAMs in the ΓX direction, and the dispersion relation was compared with that of the AAMs. The greater the number of structural units, the better the transmission of loss characteristics [28,31,32]. To obtain better sound isolation while avoiding being too large in the transmission direction, we calculated the transmission properties of three identical structural units.…”

Section: Calculation Of Transmission Propertiesmentioning

confidence: 99%

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Multi-Order Asymmetric Acoustic Metamaterials with Broad Bandgaps at Subwavelength Scales

Wang,

Chen,

2023

Materials

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Noise manipulation at the subwavelength scale remains a challenging problem. To obtain better broadband sound isolation within the subwavelength range, a class of asymmetric acoustic metamaterials (AAMs) based on rotation is proposed, and this class of AAMs can further improve subwavelength sound isolation performance by introducing multi-orders. The influences of changing the alternate propagation length of the coiled channel and the square cavity in the unit cell on the band frequency distribution and the omnidirectional band structure were investigated. The effective parameters are calculated with the S-parameter retrieval method, and the generation and change mechanisms of the bandgaps were elucidated. The calculation of sound transmission characteristics showed that, in the asymmetric mode, the overall sound isolation performance of the structure was greatly improved, and the relative bandwidth expanded as the alternate propagation length of the coiled channel and square cavity increased. The omnidirectional bandgaps from the first-order to the third-order AAMs occupied 63.6%, 75.96%, and 76.84% of the subwavelength range, respectively. In particular, the first bandgap moves to the low frequency and becomes wider. Both the experimental results and numerical analyses consistently showed that disrupting structural symmetry enhances acoustic metamaterials for superior broadband sound isolation, inspiring broader applications for asymmetry in this field.

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Section: Calculation Of Effective Parametersmentioning

confidence: 99%

Section: Calculation Of Transmission Propertiesmentioning

confidence: 99%

Multi-Order Asymmetric Acoustic Metamaterials with Broad Bandgaps at Subwavelength Scales

Wang,

Chen,

2023

Materials

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Self-aware active metamaterial cell 3D-printed in a single process

Košir,

Zupan,

Slavič

2024

International Journal of Mechanical Sciences

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On the directionality of membrane coupled Helmholtz resonators under open air conditions

Domingo-Roca,

Feeney,

Windmill

et al. 2024

Sci Rep

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Controlling the absorption and diffusion of sound in the audible range constitutes an exciting field of research. Acoustic absorbers and diffusers perform extraordinarily well at high frequencies with sizes comparable to the wavelength of the working frequency. Conversely, efficient low-frequency attenuators demand large volumes leading to unpractical sizes, and there is now interest in determining whether the size of the resonator can be reduced while not compromising – or perhaps even decreasing – the working frequency. One viable approach is through the use of metamaterials to enable the control of device dynamics such that heavy sub-wavelength attenuation can be efficiently realised. To achieve this goal, the theoretical (including a mathematical model and the use of finite element analysis) and experimental characterisation of 3D-printed membrane-coupled Helmholtz resonator (HR) acoustic metamaterials (AMMs) is explored. The results reveal good agreement between theory and experiments, and show that membrane-coupled HR AMMs feature heavy sub-wavelength acoustic attenuation (λ/55) while also showcasing directional responses under open air conditions. These features are explained by the interplay between resonator size, membrane characteristics, and the presence of two acoustic ports. It is anticipated that, together with recent advances on smart AMMs, these systems will foster new progress in the development of dynamic AMMs for wideband attenuation.

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Acoustic transmission loss in Hilbert fractal metamaterials

Cited by 7 publications

References 60 publications

Multi-Order Asymmetric Acoustic Metamaterials with Broad Bandgaps at Subwavelength Scales

Multi-Order Asymmetric Acoustic Metamaterials with Broad Bandgaps at Subwavelength Scales

Self-aware active metamaterial cell 3D-printed in a single process

On the directionality of membrane coupled Helmholtz resonators under open air conditions

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