Enhancement of sound absorption performance of Helmholtz resonators by space division and chamber grouping

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In order to achieve a balance between sound insulation and ventilation, a novel acoustic metamaterial of air-permeable multiple-parallel-connection folding chambers was proposed in this study that was based on Fano-like interference, and its sound-insulation performance was investigated through acoustic finite element simulation. Each layer of the multiple-parallel-connection folding chambers consisted of a square front panel with many apertures and a corresponding chamber with many cavities, which were able to extend both in the thickness direction and in the plane direction. Parametric analysis was conducted for the number of layers nl and turns nt, the thickness of each layer L2, the inner side lengths of the helical chamber a1, and the interval s among the various cavities. With the parameters of nl = 10, nt = 1, L2 = 10 mm, a1 = 28 mm, and s = 1 mm, there were 21 sound-transmission-loss peaks in the frequency range 200–1600 Hz, and the sound-transmission loss reached 26.05 dB, 26.85 dB, 27.03 dB, and 33.6 dB at the low frequencies 468 Hz, 525 Hz, 560 Hz, and 580 Hz, respectively. Meanwhile, the corresponding open area for air passage reached 55.18%, which yielded a capacity for both efficient ventilation and high selective-sound-insulation performance.

Section: Resultsmentioning

confidence: 99%

Study on Sound-Insulation Performance of an Acoustic Metamaterial of Air-Permeable Multiple-Parallel-Connection Folding Chambers by Acoustic Finite Element Simulation

Peng

Shen

et al. 2023

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“…Helmholtz resonators represent a canonical system for achieving sound absorption via impedance matching and resonant dissipation [37][38][39]. As shown in Figure 2, a Helmholtz resonator consists of two primary components: (1) a neck/aperture of defined size and (2) an interior cavity volume V. The resonators exhibit a strong frequency dependence dictated by their geometry.…”

Section: Concept and Theorymentioning

confidence: 99%

“…Nature provides an intriguing source of design inspiration for engineering energy dissipation and broadband absorption within synthetic cellular materials [36][37][38][39][40]. The porous morphology of wood is particularly notable, consisting of diverse vascular and fibrous cell types with multi-scale pores in the 1 µm to 1 mm size range [41,42].…”

Section: Introductionmentioning

confidence: 99%

Biomimetic Coupling Structure Increases the Noise Friction and Sound Absorption Effect

Ma,

2023

Environmental noise pollution is a growing challenge worldwide, necessitating effective sound absorption strategies to improve acoustic environments. Materials that draw inspiration from nature’s structural design principles can provide enhanced functionalities. Wood exhibits an intricate multi-scale porous architecture that can dissipate acoustic energy. This study investigates a biomimetic sound-absorbing structure composed of hierarchical pores inspired by the vascular networks within wood cells. The perforated resonators induce complementary frequency responses and porous propagation effects for broadband attenuation. Samples were fabricated using 3D printing for systematic testing. The pore size, porosity, number of layers, and order of the layers were controlled as experimental variables. Acoustic impedance tube characterization demonstrated that optimizing these architectural parameters enables absorption coefficients approaching unity across a broad frequency range. The tuned multi-layer porous architectures outperformed single pore baselines, achieving up to a 25–35% increase in the average absorption. The bio-inspired coupled pore designs also exhibited a 95% broader working bandwidth. These enhancements result from the increased viscous losses and tailored impedance matching generated by the hierarchical porosity. This work elucidates structure–property guidelines for designing biomimetic acoustic metamaterials derived from the porous morphology of wood. The results show significant promise for leveraging such multi-scale cellular geometries in future materials and devices for noise control and dissipative engineering applications across diverse sectors.

“…According to the classical acoustic-electric analogy method [34][35][36], the total acoustic impedance Z total of the SEAM-MTCs could be derived using Equation (14), and the corresponding theoretical sound absorption coefficient α could be calculated using Equation (15).…”

Section: Finite Element Simulationmentioning

confidence: 99%

Analysis of Influencing Factors for Stackable and Expandable Acoustic Metamaterial with Multiple Tortuous Channels

Bi,

Yang,

Shen

et al. 2023

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To reduce the noise generated by large mechanical equipment, a stackable and expandable acoustic metamaterial with multiple tortuous channels (SEAM–MTCs) was developed in this study. The proposed SEAM–MTCs consisted of odd panels, even panels, chambers, and a final closing plate, and these component parts could be fabricated separately and then assembled. The influencing factors, including the number of layers N, the thickness of panel t0, the size of square aperture a, and the depth of chamber T0 were investigated using acoustic finite element simulation. The sound absorption mechanism was exhibited by the distributions of the total acoustic energy density at the resonance frequencies. The number of resonance frequencies increased from 13 to 31 with the number of layers N increasing from 2 to 6, and the average sound absorption coefficients in [200 Hz, 6000 Hz] was improved from 0.5169 to 0.6160. The experimental validation of actual sound absorption coefficients in [200 Hz, 1600 Hz] showed excellent consistency with simulation data, which proved the accuracy of the finite element simulation model and the reliability of the analysis of influencing factors. The proposed SEAM–MTCs has great potential in the field of equipment noise reduction.