scholarly journals A Perforated Plate with Stepwise Apertures for Low Frequency Sound Absorption

2021 ◽  
Vol 11 (13) ◽  
pp. 6180
Author(s):  
Xin Li ◽  
Bilong Liu ◽  
Chong Qin
Keyword(s):  
3D Printing ◽  
Sound Absorption ◽  
Numerical Models ◽  
Characteristic Impedance ◽  
Perforated Plate ◽  
Low Frequency ◽  
Low Frequencies ◽  
Perforated Plates ◽  
Absorption Bandwidth ◽  
Acoustic Resistance

A perforated plate with stepwise apertures (PPSA) is proposed to improve sound absorption for low frequencies. In contrast with an ordinary perforated plate with insufficient acoustic resistance and small acoustic mass, the perforated plate with stepped holes could match the acoustic resistance of air characteristic impedance and also moderately increase acoustic mass especially at low frequencies. Prototypes made by 3D printing technology are tested in an impedance tube. The measured results agree well with that of prediction through theoretical and numerical models. In addition, an absorber array of perforated plates with stepwise apertures is presented to extend the sound absorption bandwidth due to the introduced multiple local resonances.

scholarly journals Design of Multiple Parallel-Arranged Perforated Panel Absorbers for Low Frequency Sound Absorption

Materials ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2099
Author(s):  
Xin Li ◽  
Qianqian Wu ◽  
Ludi Kang ◽  
Bilong Liu
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Normal Wave ◽  
Low Frequency ◽  
Approximation Model ◽  
Low Frequencies ◽  
Absorption Bandwidth ◽  
Frequency Sound ◽  
Electrical Analogy ◽  
Wave Incidence

A particular structure that consists of four parallel-arranged perforated panel absorbers (PPAs) is proposed for the low frequency sound absorption within a constraint space. The apertures of the perforated panels are set to ≥1.5 mm, and the number of orifices is much less and therefore easier to be produced in comparison with that of the micro perforated panel (MPP). A simple approximation model by using acoustic-electrical analogy is described to calculate the sound absorption coefficient of such device subject to normal wave incidence. Theoretical and experimental results demonstrate that the device can provide more than one octave sound absorption bandwidth at low frequencies.

Simulation research on low frequency sound absorption of monostable metamaterials

2021 ◽  
Vol 263 (6) ◽  
pp. 648-652
Author(s):  
Tuo Xing ◽  
Xianhui Li ◽  
Xiaoling Gai ◽  
Zenong Cai ◽  
Xiwen Guan
Keyword(s):  
Magnetic Field ◽  
Finite Element ◽  
Theoretical Model ◽  
Finite Element Simulation ◽  
Sound Absorption ◽  
Magnetic Force ◽  
Low Frequency ◽  
Low Frequencies ◽  
Element Simulation ◽  
Simulation Results

The monostable acoustic metamaterial is realized by placing a flexible panel with a magnetic proof mass in a symmetric magnetic field. The theoretical model of monostable metamaterials has been proposed. The method of finite element simulation is used to verify the theoretical model. The magnetic force of the symmetrical magnetic field is simplified as the relationship between force and displacement, acting on the mass. The simulation results show that as the external magnetic force increases, the peak sound absorption shifts to low frequencies. The theoretical and finite element simulation results are in good agreement.

Broadening of the Sound Absorption Bandwidth of the Perforated Panel Using a Membrane-Type Resonator

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Xuezhi Zhu ◽  
Zhaobo Chen ◽  
Yinghou Jiao ◽  
Yanpeng Wang
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Degrees Of Freedom ◽  
Low Frequency ◽  
Absorption Capacity ◽  
Sound Absorption Coefficient ◽  
Sound Waves ◽  
Frequency Range ◽  
Absorption Bandwidth ◽  
Membrane Type

In order to broaden the sound absorption bandwidth of a perforated panel in the low frequency range, a lightweight membrane-type resonator is installed in the back cavity of the perforated panel to combine into a compound sound absorber (CSA). Because of the great flexibility, the membrane-type resonator can be vibrated easily by the incident sound waves passing through the holes of the perforated panel. In the low frequency range, the membrane-type resonator and the perforated panel constitute a two degrees-of-freedom (DOF)-resonant type sound absorption system, which generates two sound absorption peaks. By tuning the parameters of the membrane type resonator, a wide frequency band having a large sound absorption coefficient can be obtained. In this paper, the sound absorption coefficient of CSA is derived analytically by combining the vibration equation of the membrane-type resonator with the acoustic impedance equation of the perforated panel. The influences of the parameters of the membrane-type resonator on the sound absorption performance of the CSA are numerically analyzed. Finally, the wide band sound absorption capacity of the CSA is validated by the experimental test.

A Preliminary Study on the Sound Absorption of Self-Facing Date Palm Fibers

2014 ◽  
Vol 565 ◽  
pp. 25-30 ◽  
Author(s):  
Elwaleed A. Khidir ◽  
N. Nikabdullah ◽  
M.J.M. Nor ◽  
M.F.Mat Tahir ◽  
M.Z. Nuawi
Keyword(s):  
Sound Absorption ◽  
Date Palm ◽  
Perforated Plate ◽  
Low Frequency ◽  
Single Layer ◽  
Absorption Properties ◽  
Date Palm Fibers ◽  
Layer Sample ◽  
Good Improvement ◽  
Preliminary Study

Sound absorption of self-facing natural date palm fibershas been investigated.A single layer sample of the fibers was tested for its sound absorption properties. The sample was then faced with the originally date palm fiber netted structure. Experimental measurements were conducted on the impedance tube at the acoustic lab, Faculty of Engineering, UniversitiKebangsaan Malaysia, to determine the sound absorption coefficient.The single layer was also tested using an aluminum perforated plate, as facing, for comparison purposes.The results show a good improvement in the sound absorption for the self-facing panel for the whole frequency range. However, when using the aluminum perforated panel an improvement in the sound absorption was observed only above 2500 Hz. The effect of introducing air gap thickness was studied. The results show improvement for the sound absorption the low frequency.

scholarly journals Numerical analyses of the sound transmission at low frequencies of a calibrated domestic wooden window

2021 ◽  
pp. 095440622110036
Author(s):  
Chaima Soussi ◽  
Mathieu Aucejo ◽  
Walid Larbi ◽  
Jean-François Deü
Keyword(s):  
Numerical Models ◽  
Low Frequency ◽  
Sound Transmission ◽  
The Finite Element Method ◽  
Acoustic Response ◽  
Frequency Range ◽  
Low Frequencies ◽  
Structure Interaction ◽  
Free Fields ◽  
Main Components

This work focuses on the numerical prediction of the sound transmission of wooden windows in the low frequency range. In this context, the finite element method is used to solve the multiphysics problem. This choice is justified by the fact that this approach is suitable for the resolution of fluid-structure interaction problems in low frequencies, due in particular to its flexibility in taking into account the coupling between domains and the geometrical and material complexities of the structures. To reach the desired objective, experimental modal analyses of the main components of a window, and then of a complete one, are performed in order to calibrate the numerical models. Then, a configuration that combines free-fields on both sides of the structure is employed to evaluate the intrinsic acoustic response of the window. The numerical results for a symmetric and an asymmetric glazing are compared to experimental ones to evaluate the efficiency and validity of the developed models.

scholarly journals Numerical Prediction of Homogeneity of Gas Flow through Perforated Plates

Processes ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 1770
Author(s):  
Kamil Śmierciew ◽  
Dariusz Butrymowicz ◽  
Jarosław Karwacki ◽  
Jerzy Gagan
Keyword(s):  
Pressure Drop ◽  
Gas Flow ◽  
Numerical Models ◽  
Perforated Plate ◽  
Total Surface Area ◽  
Structural Elements ◽  
Open Area ◽  
Perforated Plates ◽  
Porous Media Model ◽  
Flow Through

Vanes and baffles are often used as flow distributors where uniform flow is required in the apparatus of large cross-section surface areas. As an alternative, perforated plates with a range of open area ratios are applied to produce required gas flow homogeneity. Usually, the plates with various open area ratios are combined into large panels, of which total surface area can reach hundreds of square meters for large-sized industrial apparatus. Numerical modelling of the flow through such panels can be thought of as overly complex, time-consuming, and inefficient due to numerous small open area ratios in the plates and large differences in dimensions between open area ratios and free-stream areas. For this reason, numerical models of gas flow are limited to single plates only with constant open area ratios. A new indirect modelling approach of gas flow through the perforated plates panel with structural elements and various open area ratios with application of the porous media model is proposed. A perforated plate was experimentally investigated in terms of pressure drop and velocity distribution. The data obtained were used for the validation of the numerical results, which differed from the experimental results by less than 5%. In the next step, numerical analyses were performed for plates with open area ratios in the range of 30 to 70% for gas velocities of 5 and 10 m/s. A general correlation for pressure drop as a function of open area ratio was proposed. Finally, systematic numerical studies of the flow through both perforated and porous plates including structural elements were performed. The internal resistance of the porous core was calculated by means of a developed correlation. A good agreement between results with an error lower than 15% was observed.

Comparison of multiple-layer versus multiple-cavity microperforated panels for sound absorption at low frequency

2021 ◽  
Vol 69 (4) ◽  
pp. 341-350
Author(s):  
Pedro Cobo ◽  
Francisco Simón ◽  
Carlos Colina
Keyword(s):  
Sound Absorption ◽  
Low Frequency ◽  
Single Layer ◽  
Helmholtz Resonator ◽  
Layer Versus ◽  
Low Frequencies ◽  
High Frequencies ◽  
Multiple Layer ◽  
Band Absorption ◽  
Microperforated Panels

Microperforated panels (MPPs) are recognized as suitable absorbers for noise control applications demanding special clean and health requirements.While it is relatively easy to design single-layer MPPs for sound absorption in one-to-two octave bands at medium-high frequencies, the performance for low frequencies (below 600 Hz) leads to a rather narrow-band absorption, similar to that of a Helmholtz resonator. However, multiple-layer MPPs can be designed as sound absorbers that yield low-frequency absorption in a wide frequency band. Recently, multiple-cavity perforated panels have been proposed to improve the performance of MPPs in the low-frequency range. In this article, the capability of multiple-layer and multiple-cavity MPPs to provide sound absorption at low frequencies is analyzed.

Influences of the Air Layer with Irregular Shape to the Absorbing Constructions

2011 ◽  
Vol 343-344 ◽  
pp. 289-295
Author(s):  
Kai Hua Liu ◽  
Rong Ping Lai ◽  
Chuan Wen Chou
Keyword(s):  
Absorption Coefficient ◽  
Sound Absorption ◽  
Low Frequency ◽  
Past Research ◽  
Irregular Shape ◽  
Interior Space ◽  
Air Cavity ◽  
Low Frequencies ◽  
The Subject ◽  
Absorption Characteristics

Air layer with irregular shape in sound absorbing structure is formed by different structure mode of materials. With building multiform interior space by materials and structure mode, it makes the shape of air layer between the facing and the structure of building to be irregular shape.According to related study of absorbing structure, it shows less information about the influence of air layer with irregular shape. The factors of sound absorption of absorbing structure were focused on absorbing structure which facing paralleled structure of building in past research. For searching the influence of sound absorption of absorbing structure caused by the air layer with irregular shape, the subject in this study is set as the air layer with irregular shape which facing tilts with single-axis. The factors of air layer with irregular shape are the angle between tilting facing and horizontal face, the length of span of tilting facing, and if the setting is that the air layer is divided into several parts not to be interlinked. By these factors the sound absorption characteristics of air layer with irregular shape are shown.In the other point of effects of absorption coefficient causing by setting of air cavity, both panel and perforated panel structure the influences are influenced mainly at low frequency, especially at 200 Hz. Whether the air cavity is set or not, the panel structure reveals less influences and the absorption coefficient reduces as increasing of span at low frequencies.

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