scholarly journals Sound absorption of a micro-perforated plate backed by a porous material under high sound excitation: measurement and prediction

2013 ◽  
Vol 2 (4) ◽  
pp. 281 ◽  
Author(s):  
Rostand Boumda Tayong ◽  
Thomas Dupont ◽  
Philippe Leclaire
Keyword(s):  
Porous Material ◽  
Sound Absorption ◽  
Perforated Plate ◽  
Rigid Wall ◽  
Experimental Results ◽  
Mean Flow ◽  
Sound Levels ◽  
Specific Impedance ◽  
Air Flow Resistivity ◽  
High Sound

The sound absorption coefficient of perforated facings backed by porous materials is studied under high sound intensities in the absence of mean flow. The theoretical considerations are based on the equivalent fluid following the Johnson-Champoux-Allard approach and the use of the transfer matrix method. To take into account the high sound levels effects, the air flow resistivity of each layer is modified following the Forchheimer law. Two specimens of perforated plate are built and tested when backed by a polymeric foam and a fibrous material. A specific impedance tube setup is developed for the measurement of the surface acoustic impedance for sound pressure levels ranging from 90 dB to 150 dB at the surface of the perforated facing. To corroborate the validity of the presented method, two considerations are particularly depicted in the experimental results: first, the case where the perforated facing and the porous material are both directly backed by a rigid wall and the case where there is an air cavity between the porous material and the rigid wall. Good agreement is observed between the simulation and the experimental results.

scholarly journals On-demand optimize design of sound-absorbing porous material based on multi-population genetic algorithm

e-Polymers ◽  
2020 ◽  
Vol 20 (1) ◽  
pp. 122-132
Author(s):  
Yonghua Wang ◽  
Shengfu Liu ◽  
Haiquan Wu ◽  
Chengchun Zhang ◽  
Jinkai Xu ◽  
...  
Keyword(s):  
Genetic Algorithm ◽  
Porous Material ◽  
High Frequency ◽  
Population Genetic ◽  
Sound Absorption ◽  
Perforated Plate ◽  
Noise Spectrum ◽  
Absorption Effect ◽  
Absorption Performance ◽  
Population Genetic Algorithm

AbstractPorous material (PM) shows good sound absorption performance, however, the sound absorbing property of PM with different parameters are greatly different. In order to match the most suitable absorbing materials with the most satisfactory sound-absorbing performance according to the noise spectrum in different practical applications, multi-population genetic algorithm is used in this paper to optimize the parameters of porous sound absorbing structures that are commonly used according to the actual demand of noise reduction and experimental verification. The results shows that the optimization results of multi-population genetic algorithm are obviously better than the standard genetic algorithm in terms of sound absorption performance and sound absorption bandwidth. The average acoustic absorption coefficient of PM can reach above 0.6 in the range of medium frequency, and over 0.8 in the range of high frequency through optimization design. At a mid-to-high frequency environment, the PM has a better sound absorption effect and a wider frequency band than that of micro-perforated plate. However, it has a poor sound absorption effect at low frequency. So it is necessary to select suitable sound absorption material according to the actual noise spectrum.

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 Bilayer ventilated labyrinthine metasurfaces with high sound absorption and tunable bandwidth

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jiayuan Du ◽  
Yuezhou Luo ◽  
Xinyu Zhao ◽  
Xiaodong Sun ◽  
Yanan Song ◽  
...  
Keyword(s):  
Sound Absorption ◽  
Air Flow ◽  
Single Layer ◽  
Sound Waves ◽  
Acoustic Metamaterials ◽  
Sound Barrier ◽  
Free Air ◽  
Relative Bandwidth ◽  
Wide Range ◽  
High Sound

AbstractThe recent advent of acoustic metamaterials offers unprecedented opportunities for sound controlling in various occasions, whereas it remains a challenge to attain broadband high sound absorption and free air flow simultaneously. Here, we demonstrated, both theoretically and experimentally, that this problem can be overcome by using a bilayer ventilated labyrinthine metasurface. By altering the spacing between two constituent single-layer metasurfaces and adopting asymmetric losses in them, near-perfect (98.6%) absorption is achieved at resonant frequency for sound waves incident from the front. The relative bandwidth of absorption peak can be tuned in a wide range (from 12% to 80%) by adjusting the open area ratio of the structure. For sound waves from the back, the bilayer metasurface still serves as a sound barrier with low transmission. Our results present a strategy to realize high sound absorption and free air flow simultaneously, and could find applications in building acoustics and noise remediation.

scholarly journals Diffuse Sound Absorptive Properties of Parallel-Arranged Perforated Plates with Extended Tubes and Porous Materials

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1091 ◽  
Author(s):  
Dengke Li ◽  
Daoqing Chang ◽  
Bilong Liu
Keyword(s):  
Boundary Condition ◽  
Porous Material ◽  
Porous Materials ◽  
Sound Absorption ◽  
Azimuthal Angle ◽  
Octave Band ◽  
Frequency Range ◽  
Absorption Coefficients ◽  
Perforated Plates ◽  
Absorption Performance

The diffuse sound absorption was investigated theoretically and experimentally for a periodically arranged sound absorber composed of perforated plates with extended tubes (PPETs) and porous materials. The calculation formulae related to the boundary condition are derived for the periodic absorbers, and then the equations are solved numerically. The influences of the incidence and azimuthal angle, and the period of absorber arrangement are investigated on the sound absorption. The sound-absorption coefficients are tested in a standard reverberation room for a periodic absorber composed of units of three parallel-arranged PPETs and porous material. The measured 1/3-octave band sound-absorption coefficients agree well with the theoretical prediction. Both theoretical and measured results suggest that the periodic PPET absorbers have good sound-absorption performance in the low- to mid-frequency range in diffuse field.

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