scholarly journals Specific Normal Impedance and Sound Absorption Coefficients of Materials

1941 ◽  
Vol 12 (3) ◽  
pp. 470-470
Author(s):  
Paul E. Sabine
Keyword(s):  
Sound Absorption ◽  
Absorption Coefficients

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 Preparation and Characterization of Gradient Compressed Porous Metal for High-Efficiency and Thin-Thickness Acoustic Absorber

Materials ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1413 ◽  
Author(s):  
Xiaocui Yang ◽  
Xinmin Shen ◽  
Panfeng Bai ◽  
Xiaohui He ◽  
Xiaonan Zhang ◽  
...  
Keyword(s):  
Sound Absorption ◽  
High Efficiency ◽  
Structural Parameters ◽  
Porous Metal ◽  
Theoretical Models ◽  
Absorption Efficiency ◽  
Total Thickness ◽  
Porous Metals ◽  
Absorption Coefficients ◽  
Optimal Average

Increasing absorption efficiency and decreasing total thickness of the acoustic absorber is favorable to promote its practical application. Four compressed porous metals with compression ratios of 0%, 30%, 60%, and 90% were prepared to assemble the four-layer gradient compressed porous metals, which aimed to develop the acoustic absorber with high-efficiency and thin thickness. Through deriving structural parameters of thickness, porosity, and static flow resistivity for the compressed porous metals, theoretical models of sound absorption coefficients of the gradient compressed porous metals were constructed through transfer matrix method according to the Johnson–Champoux–Allard model. Sound absorption coefficients of four-layer gradient compressed porous metals with the different permutations were theoretically analyzed and experimentally measured, and the optimal average sound absorption coefficient of 60.33% in 100–6000 Hz was obtained with the total thickness of 11 mm. Sound absorption coefficients of the optimal gradient compressed porous metal were further compared with those of the simple superposed compressed porous metal, which proved that the former could obtain higher absorption efficiency with thinner thickness and fewer materials. These phenomena were explored by morphology characterizations. The developed high-efficiency and thin-thickness acoustic absorber of gradient compressed porous metal can be applied in acoustic environmental detection and industrial noise reduction.

scholarly journals COMPARATIVE ANALYSIS OF SOUND SUPRESSING LIGHTWEIGHT STRUCTURED PANELS AND MODERN NOISE PROTECTION MEANS

Akustika ◽  
2019 ◽  
Vol 32 ◽  
pp. 30-35
Author(s):  
Valery Murzinov ◽  
Pavel Murzinov ◽  
Irina Ivanovna
Keyword(s):  
Comparative Analysis ◽  
Sound Absorption ◽  
Absorption Coefficients ◽  
Acoustic Insulation ◽  
Materials Used ◽  
And Control

This article provides an overview of modern soundproof materials and structures used for acoustic insulation. Presently, we can find plenty of such noise insulation and sound absorption materials. One of the popular means to reduce noise and control sound today is the acoustic panels able to suppress and absorb different sounds. The article also analyses the effectiveness of acoustic and sound protection materials used in the industrial sphere. The comparative analysis of the sound protection and absorption effectiveness is carried out using sound absorption coefficients. It also presents the construction of a sound suppressing lightweight structured panel designed by the authors. The authors noted that these panels have better characteristics in comparison with other modern sound protection materials.

scholarly journals Effects of heat treatment on sound absorption coefficients in nanosilver‐impregnated and normal solid woods

2016 ◽  
Vol 11 (4) ◽  
pp. 365-369 ◽  
Author(s):  
Ayoub Esmailpour ◽  
Hamid Reza Taghiyari ◽  
Habib Zolfaghari
Keyword(s):  
Heat Treatment ◽  
Sound Absorption ◽  
Absorption Coefficients

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.

scholarly journals Simulation of Normal Incidence Sound Absorption Coefficients of Perforated Panels With/Without Glass Wool by Transmission Line Parameters in a Two-Port Network

2016 ◽  
Vol 44 ◽  
pp. 123-130
Author(s):  
Takayoshi Nakai
Keyword(s):  
Transmission Line ◽  
Input Impedance ◽  
Thermal Conduction ◽  
Sound Absorption ◽  
Sound Propagation ◽  
Viscous Friction ◽  
Normal Incidence ◽  
Glass Wool ◽  
Absorption Coefficients ◽  
Transfer Function Method

This paper describes simulation of normal incidence sound absorption coefficients of perforated panels by transmission line parameters in a two-port network. Maa and Sakagami have investigated micro perforated panels, MPP. But their theories can treat only near 1 % perforation rates of perforated panels with back cavities. If sound propagates as a plane wave, sound propagation can be represented as transmission line parameters in a two-port network. Perforated panels, back cavities, and glass wool absorption materials are represented as matrix of transmission line parameters, respectively. Transmission line parameters of a perforated panel with a back cavity are calculated as multiplication of their matrices. An input impedance can be calculated from the transmission line parameters. A normal incident absorption coefficient is calculated from the input impedance. Holes of the perforated panels have losses of viscous friction and thermal conduction at their walls. Simulations are done in the condition of 0.25 mm to 5 mm diameters of holes, 0.25 % to 25 % perforation rates, 0.5 mm to 5 mm thickness of the perforated panels with back cavities in which there are or are not glass wool absorption materials. The results of these simulations are good agreements with the results of our measurements by transfer function method except in the condition of more than 1 mm diameter of holes.

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