Broadening perfect sound absorption by composite absorber filled with porous material at low frequency

2020 ◽  
pp. 107754632098021
Author(s):  
Baozhu Cheng ◽  
Nansha Gao ◽  
Yunke Huang ◽  
Hong Hou
Keyword(s):  
Porous Material ◽  
Sound Absorption ◽  
Low Frequency ◽  
Material Structure ◽  
Frequency Noise ◽  
Complex Frequency ◽  
Acoustic Model ◽  
Efficient Design ◽  
Absorption Frequency ◽  
Plane Method

To enhance the low-frequency broadband sound absorption, we propose an absorber filled with porous material and establish a relative acoustic model. Based on the critical coupling condition, a Helmholtz absorber was designed to achieve perfect sound absorption at 172 Hz by the complex frequency plane method. Considering the weak adjustability and acoustic impedance of the Helmholtz absorber, we devised four absorber filled with porous material units that can achieve perfect sound absorption at discrete frequencies between 400 and 488 Hz with a thickness of only 51 mm. A composite absorber filled with porous material was designed by arranging four absorber filled with porous material units in a coplanar manner. The broadband perfect sound absorption of the composite absorber filled with porous material was subsequently verified by simulation and experiment. The thickness of the composite absorber filled with porous material is only 1/18 of the wavelength corresponding to the perfect absorption frequency, and it shows excellent subwavelength characteristics. The theoretical acoustic model of the composite absorber filled with porous material and the complex frequency plane method can achieve a more efficient design of broadband perfect sound absorbers. The composite absorber filled with porous material not only realizes low-frequency broadband perfect sound absorption but is also lightweight and easy to fabricate. This demonstrates the composite absorber filled with porous material structure has great potential for application in low to mid frequency noise control.

Low-frequency sound absorption of a tunable multilayer composite structure

2021 ◽  
pp. 107754632110082
Author(s):  
Hanbo Shao ◽  
Jincheng He ◽  
Jiang Zhu ◽  
Guoping Chen ◽  
Huan He
Keyword(s):  
Porous Material ◽  
Absorption Coefficient ◽  
Composite Structure ◽  
Low Frequency ◽  
Acoustic Absorption ◽  
Multilayer Composite ◽  
Absorption Frequency ◽  
Acoustic Absorption Coefficient ◽  
Simulation And Experiment ◽  
Single Material

Our work investigates a tunable multilayer composite structure for applications in the area of low-frequency absorption. This acoustic device is comprised of three layers, Helmholtz cavity layer, microperforated panel layer, and the porous material layer. For the simulation and experiment in our research, the absorber can fulfill a twofold requirement: the acoustic absorption coefficient can reach near 0.8 in very low frequency (400 Hz) and the range of frequency is very wide (400–3000 Hz). In all its absorption frequency, the average of the acoustic absorption coefficient is over 0.9. Besides, the absorption coefficient can be tunable by the scalable cavity. The multilayer composite structure in our article solved the disadvantages in single material. For example, small absorption coefficient in low frequency in traditional material such as microperforated panel and porous material and narrow reduction frequency range in acoustic metamaterial such as Helmholtz cavity. The design of the composite structure in our article can have more wide application than single material. It can also give us a novel idea to produce new acoustic devices.

Theoretical and numerical study of nonlinear acoustic absorbers for low frequency noise control

2021 ◽  
Vol 263 (1) ◽  
pp. 5600-5604
Author(s):  
Min Yang ◽  
Xianhui Li ◽  
Zenong Cai ◽  
Junjuan Zhao ◽  
Peng Zhang ◽  
...  
Keyword(s):  
Sound Absorption ◽  
Averaging Method ◽  
Numerical Study ◽  
Structural Parameters ◽  
Low Frequency ◽  
Frequency Noise ◽  
Flow Equations ◽  
State Response ◽  
Runge Kutta Method ◽  
Absorption Performance

In this paper, the sound absorption characteristics of cubic nonlinear sound-absorbing structures are analyzed by theoretical and numerical methods. The slow flow equations of the system are derived by using complexification averaging method, and the nonlinear equations which describe the steady- state response are obtained. The resulting equations are verified by comparing the results which respectively obtained from complexification-averaging method and Runge-Kutta method. It is helpful to optimize the structural parameters and further improve the sound absorption performance to study the variation of the sound absorption performance of cubic nonlinear structure with its structural parameters.

Design of Transformer Substation Low Frequency Sound Absorber and Test Study on Sound Absorption Property

2013 ◽  
Vol 468 ◽  
pp. 134-140 ◽  
Author(s):  
Xia Zhang ◽  
Shu Ning Duan ◽  
Mei Gen Cao ◽  
Juan Mo ◽  
Yu Han Sun ◽  
...  
Keyword(s):  
Sound Absorption ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Frequency Sound ◽  
Sound Absorber ◽  
Test Study ◽  
Transformer Substation ◽  
Cavity Thickness ◽  
Standing Wave Tube

In allusion to the characteristic that transformer noise is mainly low-frequency noise, firstly the sound absorber is studied and analyzed on aspect of materials, sound absorption structure cavity thickness and punching rate etc in standing wave tube laboratory, secondly transformer substation low-frequency sound absorber is presented, and finally sound absorption properties of absorber is verified through random incidence Test. The analyses and study indicates that: compared with thin plate resonance absorber and micropunching sound absorber, the sound absorption band width of transformer substation low-frequency sound absorber has been improved under unchanged sound absorption effect and transformer low-frequency noise may be effectively absorbed.

scholarly journals Sound Absorption Performance of Aluminum Silicate Fiber for Noise and Vibration Reduction of Distribution Transformer

2022 ◽  
Vol 2152 (1) ◽  
pp. 012037
Author(s):  
Qunli Chen ◽  
Wengeng Wu ◽  
Xu Gao ◽  
Yibiao Huang ◽  
Xiangwen Chen ◽  
...  
Keyword(s):  
Sound Absorption ◽  
Plate Thickness ◽  
Low Frequency ◽  
Unit Weight ◽  
Aluminum Silicate ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Absorption Performance ◽  
Cavity Thickness ◽  
Noise And Vibration Reduction

Abstract In view of the low-frequency noise problem in urban substation, the sound absorption (SA) properties of aluminum silicate fibers (ASF) with different materials, unit weight, plate thickness and cavity thickness were tested in this paper. It was found that the high-purity ASF with larger unit weight, plate thickness and cavity thickness had larger low-frequency SA coefficient, which provided technical support for the development of new low-frequency noise reduction materials for substation.

The Mechanisms of Passive Ear Defenders

2002 ◽  
Vol 33 (5) ◽  
pp. 13-21 ◽  
Author(s):  
M. R. Paurobally ◽  
J. Pan
Keyword(s):  
Sound Absorption ◽  
Theoretical Study ◽  
Active Noise Control ◽  
Low Frequency ◽  
The Other ◽  
Frequency Noise ◽  
Transmission Characteristics ◽  
Active Noise ◽  
Theoretical Predictions

In this paper a model of the sound transmission characteristics of a conventional circumaural passive ear protector is presented for low frequency noise. It includes the effects of porous sound absorption material within the device as well as sound leakage. A theoretical study based on the model shows that the presence of sound absorption material effectively acts to increase the volume compliance of the system, thus decreasing its resonance frequency. The role of leakage on the other hand is mainly to shift the resonance to a higher frequency depending on the equivalent leakage diameter. Experimental results are provided in support of the theoretical predictions. The model is useful in providing an understanding of the mechanisms of conventional passive ear defenders and can be employed to guide their design. The modelling can also be extended to study and aid in the development of communication and active noise control ear protectors.

Theoretical End Experimental Evaluation of Perforations Effect on Sound Insulation

2017 ◽  
Author(s):  
Olga Khrystoslavenko ◽  
Raimondas Grubliauskas
Keyword(s):  
Noise Reduction ◽  
High Frequency ◽  
Sound Absorption ◽  
Low Frequency ◽  
Experimental Methods ◽  
Glass Wool ◽  
Acoustic Properties ◽  
Sound Insulation ◽  
Frequency Noise ◽  
Sound Reduction

To design a sound-absorbing panel, it is important to identify factors that affect the maximum sound absorption of low, middle and high frequency sounds. Perforation effect is very important for the noise-reducing and noiseabsorbing panels. Perforations are often used for sound reduction. Experimental data shows that the perforation is very effective to absorb low-frequency noise. In the presented study, influence of perforation coefficient of noise reduction was analyzed with theoretical and experimental methods. The experiments were conducted in noise reduction chamber using an perforated construction with glass wool filler. Sound reductions index of 15 dB indicates good acoustic properties of the panel.

scholarly journals A parameter design method for multifrequency perfect sound-absorbing metasurface with critical coupled Helmholtz resonator

2021 ◽  
pp. 146134842110196
Author(s):  
Sun Wei ◽  
Li Li ◽  
Chu Zhigang ◽  
Li Linyong ◽  
Fan Xiaopeng
Keyword(s):  
Sound Absorption ◽  
Design Method ◽  
Structural Parameters ◽  
Low Frequency ◽  
Helmholtz Resonator ◽  
Programming Algorithm ◽  
Structural Parameter ◽  
Efficient Design ◽  
Harmonic Components ◽  
Frequency Harmonic

The low-frequency harmonic components of urban substation noise are easy to annoy the residents. Multi-frequency perfect sound-absorbing metasurface based on the Helmholtz resonator (HR) is an alternative solution to suppress the low-frequency harmonic noise. This paper proposes an efficient design method of structural parameter for the multi-frequency perfect sound-absorbing metasurface. Taking the perfect sound absorption at the target frequency as objective and the structural parameters of HR as optimization variables, the structural parameter optimization model of multi-frequency perfect sound-absorbing metasurface is established and solved by the sequential quadratic programming algorithm. The proposed design method effectively overcomes the deterioration of sound absorption performance caused by the combined design of multiple perfect sound absorption units. Utilizing the proposed method, we designed a multi-frequency perfect sound-absorbing metasurface to absorb the four harmonic components of an urban substation noise simultaneously. The finite element simulation results and the experimental results of the physical sample indicate that the designed multi-frequency perfect sound-absorbing metasurface can satisfy critical coupling to achieve perfect sound absorption at all target frequencies.

scholarly journals Improved Sound Absorption Properties in Polyurethane Foams by the Inclusion of Al2O3 Nanoparticles

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Binxia Yuan ◽  
Xinyi Fang ◽  
Jianben Liu ◽  
Yan Liu ◽  
Rui Zhu
Keyword(s):  
Energy Dissipation ◽  
Absorption Coefficient ◽  
Sound Absorption ◽  
Low Frequency ◽  
Acoustic Energy ◽  
Sound Absorption Coefficient ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Dissipation Process ◽  
Single Hole

At present, the scale of China’s power grid is becoming larger and larger, and the control of low-frequency noise in substations (especially for transformers) is very important. The sound-absorbing materials have become one of the important ways to control low-frequency noise. The single polyurethane material cannot satisfy the requirements for reducing low-frequency noise, so it is very necessary to study its composite with other materials. In the paper, the flexible polyurethane foam and Al2O3 nanoparticle composites were obtained by the impregnation method. The method was simple, safe, and easy to control. The morphology and sound absorption coefficient of the foam materials before and after filling were analyzed. Single-hole acoustic cavity models of PU and Al2O3-PU composite were established through the finite element. The absorption and dissipation process of sound pressure for single hole was studied to understand the energy dissipation process. Meanwhile, through studying acoustic energy storage and acoustic energy dissipation, the loss factor of a single hole was obtained, which can predict the change rule of the sound absorption coefficient for PU foam and Al2O3-PU.

scholarly journals Enhanced Low-Frequency Sound Absorption of a Porous Layer Mosaicked with Perforated Resonator

Polymers ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 223
Author(s):  
Xin Li ◽  
Bilong Liu ◽  
Qianqian Wu
Keyword(s):  
Porous Material ◽  
Absorption Coefficient ◽  
Porous Layer ◽  
Acoustic Impedance ◽  
Sound Absorption ◽  
Perforated Plate ◽  
Low Frequency ◽  
Sound Absorption Coefficient ◽  
Frequency Sound ◽  
Two Samples

A composite structure composed of a porous-material layer mosaicked with a perforated resonator is proposed to improve the low-frequency sound absorption of the porous layer. This structure is investigated in the form of a porous-material matrix (PM) and a perforated resonator (PR), and the PR is a thin perforated plate filled with porous material in its back cavity. Theoretical and numerical models are established to predict the acoustic impedance and sound absorption coefficient of the proposed structure, and two samples made of polyurethane and melamine, respectively, are tested in an impedance tube. The predicted results are consistent with that of the measured. Compared with a single porous layer with the same thickness, the results show that the designed structure provides an additional sound absorption peak at low frequencies. The proposed structure is compact and has an effective absorption bandwidth of more than two octaves especially below the frequency corresponding to 1/4 wavelength. A comparison is also made between the sound absorption coefficients of the proposed structure and a classical micro-perforated plate (MPP), and the results reveal equivalent acoustic performance, suggesting that it can be used as an alternative to the MPP for low–mid frequency sound absorption. Moreover, the influences of the main parameters on the sound absorption coefficient of PPCS are also analyzed, such as the hole diameter, area ratio, flow resistance, and porous-material thickness in the PR. The mechanism of sound absorption is discussed through the surface acoustic impedance and the distributions of particle velocity and sound pressure at several specific frequencies. This work provides a new idea for the applications of the thin porous layer in low- and medium-frequency sound absorption.

scholarly journals Analysis of Sound Absorption Characteristics of Acoustic Ducts with Periodic Additional Multi-Local Resonant Cavities

Symmetry ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2233
Author(s):  
Junyi Liu ◽  
Ting Wang ◽  
Meixia Chen
Keyword(s):  
Sound Absorption ◽  
Transmission Loss ◽  
Resonant Cavity ◽  
Low Frequency ◽  
Additional Mass ◽  
Resonant Cavities ◽  
Absorption Frequency ◽  
Frequency Sound ◽  
Cavity Structure ◽  
Absorption Characteristics

With the aim of applying various Helmholtz resonant cavities to achieve low-frequency sound absorption structures, a pipe structure with periodic, additional, symmetrical, multi-local resonant cavities is proposed. A thin plate with additional mass is placed in the cylindrical Helmholtz resonant cavity structure to form a symmetric resonant cavity structure and achieve multi-local resonance. The simulation results show that the periodic structure proposed in this paper can produce multiple, high acoustic transmission loss peaks and multiple lower broadband sound absorption frequency bands in the low-frequency range. In this paper, this idea is also extended to the Helmholtz resonant cavity embedded with multiple additional mass plates. The results show that the periodic arrangement of the multi-local resonant symmetric cavity inserted into multiple plates with mass can significantly increase its transmission loss and show a better performance on low-frequency sound absorption characteristics.

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