Enhancement of sound absorption in a band frequency using thin porous layer-lined metasurfaces

2021 ◽  
Vol 263 (1) ◽  
pp. 5097-5100
Author(s):  
Joong Seok Lee ◽  
Jun Hyeong Park ◽  
Pyung Sik Ma ◽  
Shin Young Kim ◽  
Yoon Young Kim
Keyword(s):  
Porous Layer ◽  
Sound Absorption ◽  
Sound Field ◽  
Band Frequency ◽  
Porous Layers ◽  
Material Parameters ◽  
Quarter Wavelength ◽  
Key Factor ◽  
New Type ◽  
Absorption Performance

When a porous layer is installed on a hard wall, sound absorption performance is mainly determined by thickness of the layer. Although material parameters of porous materials are strongly dependent on frequencies, the thickness limitation related to the quarter wavelength of incident sound wave has been a key factor in the treatment of porous layers for noise reduction. This implies that a thicker porous layer is required to absorb lower-frequency sound effectively. To overcome the thickness limitation, metaporous layers, which are named as a compound of sound absorbing porous layers with the concept of metamaterials have received much attentions for alternative implementations of porous layers. Recently, we proposed a new type of metaporous layer for enhancing sound absorption performance in a specified broad frequency band. The proposed metaporous layer is constructed with a thin porous layer backed by a reactive metasurface consisting of an array of bent channels. Formation of sound absorption band is directly determined by the characteristics of scattered sound field from the proposed metaporous layer. Analytical and numerical investigations show that the metasurface is considerably responsible for the enhanced sound absorption in the proposed metaporous layer, while sound dissipation occurs only in the thin porous layer.

The Structural Design of Combined Absorber Composed by MPP and Multi-Layer Porous Material Based on VA One

2012 ◽  
Vol 571 ◽  
pp. 91-96
Author(s):  
Xiu Hua Duan ◽  
Huan Qin Wang ◽  
Wen Juan Sun ◽  
De Yi Kong ◽  
Zhan Zhao
Keyword(s):  
Optimal Design ◽  
Porous Material ◽  
Porous Materials ◽  
Porous Layer ◽  
Structural Design ◽  
Sound Absorption ◽  
New Method ◽  
Optimum Location ◽  
Absorption Performance

Some experiments found that the low-frequncy sound absorption performance can be improved by inserting MPP into the multi-layer porous materials, but the theory modeling of this MPP-multi-layer porous combined absorber is too difficult to provide the guidance. Therefore, a new method is proposed in this paper, according to Atalla’s theory, the MPP can be treated as a rigid porous layer in this composite absorber, then the acoustic software (such as VA One) usually for dealing with multi-layer porous absorber can be chosen to its optimal design. Based on this method, a two-layer porous absorber is designed using the Foam Module of VA One, and the influence of different insert location of MPP in the two-layer porous absorber is analyzed, which shows the existence of optimum location. Moreover, the sound absorption of different MPP structure at the optimum location is also discussed which shows inserting the wider-band MPP structure is better.

Sound absorption performance of flexible polyurethane/silicon dioxide perforated coating composites

2021 ◽  
pp. 004051752110155
Author(s):  
Min Peng ◽  
Xiaoming Zhao ◽  
Weibin Li
Keyword(s):  
Silicon Dioxide ◽  
Sound Absorption ◽  
Woven Fabric ◽  
Perforation Rate ◽  
Cavity Depth ◽  
Resonant Frequencies ◽  
The Matrix ◽  
Absorption Performance ◽  
Traditional Sense ◽  
Flexible Polyurethane

Perforated materials in the traditional sense are rigid, usually dense, costly and inflexible. For this study, polyester/cotton blended woven fabric as the base fabric, nano-SiO2 (silicon dioxide) as the functional particles and PU (polyurethane) as the matrix were selected. Accordingly, flexible PU/SiO2 perforated coating composites with different process parameters were developed. The influence of the nano-SiO2 content, perforation diameter, perforation rate, number of fiber felt layers and cavity depth on the sound absorption coefficient were investigated. The resonant frequencies of materials with different cavity depths were evaluated by both theoretical calculation and experimental method. It was found that the flexible perforated composite has good sound absorption and mechanical properties, and has great potential for applications requiring soft and lightweight sound absorption materials.

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.

scholarly journals Application of transparent microperforated panel to acrylic partitions for desktop use: A case study by prototyping

2021 ◽  
Author(s):  
Kimihiro Sakagami ◽  
Midori Kusaka ◽  
Takeshi Okuzono ◽  
Shigeyuki Kido ◽  
Daichi Yamaguchi
Keyword(s):  
Adverse Effect ◽  
Sound Absorption ◽  
Acoustic Environment ◽  
Actual Use ◽  
Acrylic Sheet ◽  
Absorption Performance ◽  
The Subject ◽  
Droplet Penetration ◽  
Absorption Characteristics

There are various measures currently in place to prevent the spread of COVID-19; however, in some cases, these can have an adverse effect on the acoustic environment in buildings. For example, transparent acrylic partitions are often used in eating establishments, meeting rooms, offices, etc., to prevent droplet infection. However, acrylic partitions are acoustically reflective; therefore, reflected sounds may cause acoustic problems such as difficulties in conversation or the leakage of conversation. In this study, we performed a prototyping of transparent acrylic partitions to which a microperforated panel (MPP) was applied for sound absorption while maintaining transparency. The proposed partition is a triple-leaf acrylic partition with a single acrylic sheet without holes between two MPP sheets, as including a hole-free panel is important to a possible droplet penetration. The sound absorption characteristics were investigated by measuring the sound absorption in a reverberation room. As the original prototype showed sound absorption characteristics with a gentle peak and low values due to the openings on the periphery, it was modified by closing the openings of the top and sides. The sound absorption performance was improved to some extent when the top and sides were closed, although there remains the possibility of further improvement. This time, only the sound absorption characteristics were examined in the prototype experiments. The effects during actual use will be the subject of future study.

scholarly journals Mixed Convection in Superposed Nanofluid and Porous Layers Inside Lid-Driven Square Cavity

2015 ◽  
Vol 10 (2) ◽  
Keyword(s):  
Mixed Convection ◽  
Porous Layer ◽  
Volume Fraction ◽  
Darcy Number ◽  
Momentum Exchange ◽  
Square Cavity ◽  
Porous Layers ◽  
Adverse Action ◽  
Nanoparticles Volume Fraction ◽  
The Right

Mixed convection in a lid-driven composite square cavity is studied numerically. The cavity is composed of two layers; a Cu–water nanofluid layer superposed a porous layer. The porous layer is saturated with the same nanofluid. The left and right walls of the cavity are thermally insulated. The bottom wall which is in contact with the porous layer is isothermally heated and being lid to the left, while the top wall is isothermally cooled and being lid to the right. Cavity walls are impermeable except the interface between the porous layer and the nanofluid. Maxwell-Brinkman model is invoked for the momentum exchange within the porous layer. Equations govern the conservation of mass, momentum, and energy within the two layers were modeled and solved numerically using under successive relaxation (USR) up- wind finite difference scheme. Four pertinent parameters are studied; nanoparticles volume fraction φ (0.0 - 0.05), porous layer thickness Wp (0.1 - 0.9), Darcy number Da (10-7 – 10-1), and Richardson number Ri (0.01 - 10). The results have showed that the existence of the porous layer in a specified value can enhance the convective heat transfer when Ri ≥ 1, while an adverse action of nanoparticles is recorded when Da ≥ 10-4.

Empirical study on the correlation between measurement methods under diffuse and direct sound field conditions for determining sound absorption and airborne sound insulation properties of noise barriers

2021 ◽  
Vol 263 (3) ◽  
pp. 3350-3361
Author(s):  
Andreas Fuchs ◽  
Reinhard Wehr ◽  
Marco Conter
Keyword(s):  
Empirical Study ◽  
Sound Absorption ◽  
Sound Field ◽  
Research Programme ◽  
Measurement Methods ◽  
Field Conditions ◽  
Acoustic Properties ◽  
Sound Insulation ◽  
Noise Barriers ◽  
Airborne Sound

In the frame of the SOPRANOISE project (funded by CEDR in the Transnational Road Research Programme 2018) the database of the European noise barrier market developed during the QUIESST project was updated with newly acquired data. This database gives the opportunity for an empirical study on the correlation between the different measurement methods for the acoustic properties of noise barriers (according to the EN 1793 series) to further investigate the interrelationships between these methods by using single-number ratings and third-octave band data. First a correlation of the measurement methods for sound absorption under diffuse field conditions (EN 1793-1) and sound reflection under direct sound field conditions (EN 1793-5) is presented. Secondly, a correlation of the measurement methods for airborne sound insulation under diffuse field conditions (EN 1793-2) and airborne sound insulation under direct sound field conditions (EN 1793-6) is shown. While for airborne sound insulation a distinct correlation is found due to the wide data range, for sound absorption no robust correlation can be found.

Sound absorption of a finite flexible micro-perforated panel absorber back by a rigid air cavity filled with a fibrous porous material

2021 ◽  
Vol 263 (3) ◽  
pp. 3625-3632
Author(s):  
Ho Yong Kim ◽  
Yeon June Kang
Keyword(s):  
Energy Dissipation ◽  
Porous Material ◽  
Fibrous Material ◽  
Alternative Energy ◽  
Sound Absorption ◽  
Sound Pressure ◽  
Absorption Coefficients ◽  
Air Cavity ◽  
Acoustic Cavity ◽  
Absorption Performance

Back by a rigid cavity filled with a layer of porous layer, the sound absorption performance of a micro-perforated panel (MPP) can be enhanced in comparison with other resonance based sound absorbers. In this paper, a theoretical model of a finite flexible MPP back by a rigid air cavity filled with a fibrous porous material is developed to predict normal sound absorption coefficients. Displacements of MPP and sound pressure field in fibrous porous material and acoustic cavity are expressed using a series of modal functions, and the sound absorption coefficients of MPP system are obtained. Additionally, comparison of energy dissipation by MPP and fibrous material is performed to identify effects of a fibrous material on the sound absorption of a MPP. As expected, at anti-resonance frequency of an MPP, the fibrous material provide an alternative energy dissipation mechanism.

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