Simulation of normal incidence sound absorption coefficients of perforated panels with/without glass wool by transmission line parameters in a two- port network

2013 ◽  
Vol 133 (5) ◽  
pp. 3309-3309
Author(s):  
Takayoshi Nakai ◽  
Kota Yoshida
Keyword(s):  
Transmission Line ◽  
Sound Absorption ◽  
Normal Incidence ◽  
Glass Wool ◽  
Absorption Coefficients

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.

Sound Absorption Characteristics of Porous Steel Manufactured by Lost Carbonate Sintering

2009 ◽  
Vol 1188 ◽  
Author(s):  
Miao Lu ◽  
Carl Hopkins ◽  
Yuyuan Zhao ◽  
Gary Seiffert
Keyword(s):  
Absorption Coefficient ◽  
Pore Size ◽  
Sound Absorption ◽  
Single Layer ◽  
Normal Incidence ◽  
Sound Absorption Coefficient ◽  
Absorption Coefficients ◽  
Impedance Tube ◽  
Absorption Characteristics

AbstractThis paper investigates the sound absorption characteristics of porous steel samples manufactured by Lost Carbonate Sintering. Measurements of the normal incidence sound absorption coefficient were made using an impedance tube for single-layer porous steel discs and assemblies comprising four layers of porous steel discs. The sound absorption coefficient was found not to vary significantly with pore size in the range of 250-1500 μm. In general, the absorption coefficient increases with increasing frequency and increasing thickness, and peaks at specific frequencies depending on the porosity. An increase in porosity tends to increase the frequency at which the sound absorption coefficient reaches this peak. An advantage was found in using an assembly of samples with gradient porosities of 75%-70%-65%-60% as it gave higher and more uniform sound absorption coefficients than an assembly with porosities of 75%.

scholarly journals Angle-Dependent Absorption of Sound on Porous Materials

Acoustics ◽  
2020 ◽  
Vol 2 (4) ◽  
pp. 753-765
Author(s):  
Jose Cucharero ◽  
Tuomas Hänninen ◽  
Tapio Lokki
Keyword(s):  
Sound Absorption ◽  
Glass Wool ◽  
Room Acoustics ◽  
Sound Waves ◽  
Absorption Coefficients ◽  
Reverberation Chamber ◽  
Impedance Tube ◽  
Material Development ◽  
Dependent Absorption ◽  
Good Agreement

Sound-absorbing materials are usually measured in a reverberation chamber (diffuse field condition) or in an impedance tube (normal sound incidence). In this paper, we show how angle-dependent absorption coefficients could be measured in a factory-type setting. The results confirm that the materials have different attenuation behavior to sound waves coming from different directions. Furthermore, the results are in good agreement with sound absorption coefficients measured for comparison in a reverberation room and in an impedance tube. In addition, we introduce a biofiber-based material that has similar sound absorption characteristics to glass-wool. The angle-dependent absorption coefficients are important information in material development and in room acoustics modeling.

Analysis of Absorption Coefficient for Eco-Friendly Acoustical Absorbers

2013 ◽  
Vol 831 ◽  
pp. 58-61
Author(s):  
Jun Oh Yeon ◽  
Kyoung Woo Kim
Keyword(s):  
Absorption Coefficient ◽  
Noise Reduction ◽  
Sound Absorption ◽  
Glass Wool ◽  
Absorption Coefficients ◽  
Sound Absorber ◽  
Reduction Coefficient ◽  
Absorption Performance ◽  
Rock Wool

Primarily used for domestic buildings as a sound absorber are glass wool, rock wool, etc. These absorbers as well as waste absorber created by recycling wastes, PP+PET fiber absorber made from polypropylene and polyester, wood wool board bonded with finely sliced roots of trees and foamed aluminum absorber are recyclable eco-friendly absorbers that are constantly being developed. In this study, we compared the sound absorption performance of currently used absorbers and eco-friendly building absorbers. As a result, the NRC (Noise Reduction Coefficient) was found to be 0.85 for glass wool, 0.95 for rock wool, and 0.70 for polyester, 0.65 for waste absorber, 0.75 for PET+ PP fiber absorber, 0.40 for wood wool board, and 0.75 for foamed aluminum absorber. Based on the results of these absorption coefficients, we expect the usability of the absorbers continues to increase as future eco-friendly building absorbers.

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.

Trial applications at gymnasiums of in-situ sound absorption measurement method by ensemble averaging technique

2021 ◽  
Vol 263 (2) ◽  
pp. 4532-4537
Author(s):  
Toru Otsuru ◽  
Reiji Tomiku ◽  
Noriko Okamoto ◽  
Siwat Lawanwadeekul
Keyword(s):  
Measurement Method ◽  
Sound Absorption ◽  
Glass Wool ◽  
Absorption Measurement ◽  
Ensemble Averaging ◽  
Averaging Technique ◽  
In Situ Conditions ◽  
Measurement Consistency ◽  
Absorption Characteristics

The authors have been published a series of papers on a measurement method for sound absorption characteristics of materials using ensemble averaging technique, i.e., EA method. The papers' results included measurement mechanisms, measurement uncertainty, and so on. Herein, to examine adaptability, especially in in-situ conditions, the EA method is applied to measure absorption characteristics of materials installed in two gymnasiums. A glass-wool panel with the dimension of 0.5 m by 0.5 m by 0.05 m and with the density of 32 kg m^-3 was brought around and measured to check the measurement consistency. Several measurements were conducted during badminton plays were undergoing. Measured sound absorption coefficients revealed that most results agree well with those measured in reverberation rooms. Certain improvement is necessary for the specimen brought to the in-situ measurement to keep the consistency. The inconsistency is considered to originate from unstable conditions between the specimen and floor.

Material Parameter Determination in Glass Wool Mat for Sound Absorption

2011 ◽  
Vol 148-149 ◽  
pp. 1271-1275 ◽  
Author(s):  
Cheng Dong Li ◽  
Zhao Feng Chen ◽  
Jie Ming Zhou ◽  
Bin Bin Li ◽  
Wang Ping Wu ◽  
...  
Keyword(s):  
Absorption Coefficient ◽  
Prediction Error ◽  
Fiber Length ◽  
Normal Incidence ◽  
Glass Wool ◽  
Parameter Determination ◽  
Frequency Range ◽  
Material Parameters ◽  
Refrigeration Equipment ◽  
Building Engineering

Glass wool mat is widely used in the fields of building engineering, transport facilities and refrigeration equipment. In this paper, the effect of material parameters such as density, thickness, porosity, and flow resistivity on the normal incidence absorption coefficient has been studied. In addition, fiber length is also investigated to achieve appropriate strength. The prediction error of normal incidence absorption coefficient by modified Johnson–Allard model is less than 5% in the frequency range between 800 Hz and 5 kHz. We could use the modified Johnson–Allard model to determine the parameter of glass wool mat for better development.

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