Development of Adjustable Parallel Helmholtz Acoustic Metamaterial for Broad Low-Frequency Sound Absorption Band

Abstract

For the common difficulties of noise control in a low frequency region, an adjustable parallel Helmholtz acoustic metamaterial (APH-AM) was developed to gain broad sound absorption band by introducing multiple resonant chambers to enlarge the absorption bandwidth and tuning length of rear cavity for each chamber. Based on the coupling analysis of double resonators, the generation mechanism of broad sound absorption by adjusting the structural parameters was analyzed, which provided a foundation for the development of APH-AM with tunable chambers. Different from other optimization designs by theoretical modeling or finite element simulation, the adjustment of sound absorption performance for the proposed APH-AM could be directly conducted in transfer function tube measurement by changing the length of rear cavity for each chamber. According to optimization process of APH-AM, The target for all sound absorption coefficients above 0.9 was achieved in 602–1287 Hz with normal incidence and that for all sound absorption coefficients above 0.85 was obtained in 618–1482 Hz. The distributions of sound pressure for peak absorption frequency points were obtained in the finite element simulation, which could exhibit its sound absorption mechanism. Meanwhile, the sound absorption performance of the APH-AM with larger length of the aperture and that with smaller diameter of the aperture were discussed by finite element simulation, which could further show the potential of APH-AM in the low-frequency sound absorption. The proposed APH-AM could improve efficiency and accuracy in adjusting sound absorption performance purposefully, which would promote its practical application in low-frequency noise control.

Research on the Sound Insulation Performance of Composite Rubber Reinforced with Hollow Glass Microsphere Based on Acoustic Finite Element Simulation

“…In order to improve the research efficiency and reduce the experiment cost, the acoustic finite element simulation has been widely utilized in the field of sound insulation and noise reduction [ 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ]. Okuzono et al [ 30 ] applied the finite element method using hexahedral 27-node spline acoustic elements with low numerical dispersion for the room acoustics simulation in both the frequency and time domains.…”

“…The finite element analysis procedure was selected by Abdullahi and Oyadiji [ 34 ] to simulate wave propagation in air-filled pipes, which was essential in the study of wave propagation in pipe networks such as oil and gas pipelines and urban water distribution networks. Yang et al [ 35 ] used the finite element method to exhibit the sound absorption mechanism of adjustable parallel Helmholtz acoustic metamaterial through the distribution of sound pressures for the peak absorption frequency points. Van Genechten et al [ 36 ] developed a hybrid simulation technique for coupled structural-acoustic analysis, which included a wave-based model for acoustic cavity and a direct- or modally-reduced finite element model for the structural part.…”

Mathematical Model for Estimating the Sound Absorption Coefficient in Grid Network Structures

“…Although the finite element method [ 11 , 12 ] is useful in the analysis of acoustic metamaterials, the simpler transfer matrix method was used in this work. The one-dimensional transfer matrix method was used to develop a simple mathematical model for accurately estimating the sound absorption coefficient of a grid network structure.…”

Metasurface acoustic liner of engine based on asymmetric absorber

“…尤其是当强迫频率较高时，孔隙率增加导致吸声系数显著增加。N.K. Jhad 等人 [8] 对均匀和混合孔隙率的微穿孔板声衬进行了理论和实验研究，发现孔隙率相 同时，孔颈越小，吸声系数越大。Martin Dannemann 等人 [9] 和 Karsten Knobloch 等人 [10] 通过柔性聚合物膜代替蜂窝芯结构中的刚性单元壁能使声衬有更大的吸 声宽带。Frank Simon [11] 为了解决低比率"板厚/孔径"产生的阻抗水平取决于 入射声压水平和掠射平均流(通过涡流脱落的非线性耗散机制)的问题，设计 了一种不同长度内插长弹性开口颈声谐振器，实验表明，在 0.3 的大马赫数下 的掠流对阻抗值影响很小。此外，也有人在声衬里添加填充物提高降噪效果， Constantin Sandu 等人研究 [12] 了摩擦粉对发动机声衬的影响，发现用各种轻质材 料支撑的细粉末填充在声衬的蜂窝状单元后，吸收频带明显变宽。总之，传统 声衬设计方法很难解决中低频降噪问题，因此设计低频、薄层的声衬成为了发 动机降噪的关键瓶颈问题。 近年来，声学超材料开始蓬勃发展，大量学者将声学超表面理论应用到声 衬设计中，设计出各种低频、薄层、宽带的新型声衬结构 [13][14][15][16][17][18][19][20][21][22] 。如，Li 团队 [13] 将内插管引入 Helmholtz 共振器中，能够降低共振频率的同时，不改变空腔体 积，从而使得结构更紧凑。为了进一步得到宽频的降噪结构，他们把多个弱共 振的 Helmholtz 共振器耦合在一起得到了结构紧凑、吸声系数高的吸声器，然 后将此吸声器与穿孔板相结合，在仅 3.9 cm 的超薄厚度实现了 870Hz 至 3224…”

“…Hz 的准完美吸收 [14] ，然后对其进行了优化设计，用于声衬结构设计，并分析了 3 流速对其降噪效果的影响 [15] 。他们还设计了一种谐振结构和多孔材料相干耦合 来提升吸声效率的声衬，在仅 4cm 的厚度支持从 800Hz 到 3200Hz 的高效吸声 [16] 。Baozhu Cheng 等人 [17] 也在内插管 Helmholtz 里填充多孔材料，增强了低频 宽带吸声。Xiaocui Yang 等人 [18] 通过引入多个谐振腔来扩大每个腔的后腔吸收 带宽和调谐长度，从而获得宽的吸声频带。Enshuai Wang 等人 [19] 设计了一种方 形并联 Helmholtz 共振器可以通过参数优化实现低频噪声控制。Benjamin S.…”