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For a 2D PnC along the D-X-M-D route in the square Brillouin zone, there are no stop bands in the frequency range between ten to 109 kHz, with u03c9 = u03c9 for a 2D PnC.
Sound-proofing ventilation barriers have been used in a variety of industries. Here we display a subwavelength acoustic metamaterial based on labyrinthine structures with tunable sound insulation and ventilation characteristics. The disruption between the resonant scattering of discrete states and continuous state scattering is caused by Fano-like asymmetric transmission dips. The sound insulation dip frequency can change from 360 Hz to 575 Hz by changing the spacing between these two half zigzag molds, although the free ventilation area ratio is maintained to over 36 percent and total thickness is only 0. 06 bb.
In high-speed automobiles, light-weight and high-stiffness honeycomb sandwich plates are widely used. An efficient way of noise reduction is by a chaotic band of nonlinear acoustic metamaterials. Based on numerical and experimental methods, this paper introduces a NAM sandwich plate and investigates its vibration reduction characteristics. Based on the same homogeneous model and experiments, we developed its nonlinear finite element model. With only 17. 7 percent attached mass, we can show that all resonances of the high-stiffness NAM plate below 800 Hz are significantly reduced, particularly the first low-frequency resonance at 93 Hz, which is reduced by 20 dB. This shows that the NAM's NAM plan can robustly and effectively reduce the low-frequency and broadband vibration of the light-weight and high-stiffness plates with little mass cost, which is a desired result for wide-ranging applications.
An optimal simulation strategy incorporating the finite element simulation and cuckoo search algorithms was recommended to achieve the broadband sound absorption at low frequencies within a limited area. According to the actual noise reduction challenges, the initial geometric parameters of the investigated acoustic metamaterials were reported first, reducing the optimization burden and increasing the optimization effectiveness. Many of the experimental findings, which also confirmed the stability of this effective design technique, were closer to the experimental findings than those estimated sound absorption coefficients by theoretical simulation.
Broadband sound absorption has always been a challenge when it comes to creating underwater sound absorption structure. The average sound absorption coefficient has increased by nearly 17%, and the sound absorption benefit of the sound absorption covers to each frequency point, which is consistent with our anticipation. This study, as well as applying membrane-type metamaterials to the design process of underwater acoustic structures, has a huge application in acoustic wave communication and device compatibility design technologies.
An adjustable parallel Helmholtz acoustic metamaterial was introduced to broaden the sound absorption band by adding multiple resonant chambers to broaden the absorption range and tuning length of each chamber for each chamber, overcoming the common challenges of noise control in a low frequency area. In the finite element simulation, which may demonstrate its sound absorption mechanism, the distributions of sound pressure for peak absorption frequency points were found. The performance of the APH-AM with longer length of the aperture and smaller diameter of the aperture were discussed by finite element simulation, which could even show the promise of APH-AM in low-frequency sound absorption.
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