Boundary condition effects of porous material in absorption measurements: Comparison of two impedance tubes

2018 ◽  
Vol 143 (3) ◽  
pp. 1836-1836
Author(s):  
Bárbara Fengler ◽  
William D. Fonseca ◽  
Paulo Mareze ◽  
Eric Brandao ◽  
ARTUR Zorzo
Keyword(s):  
Boundary Condition ◽  
Porous Material ◽  
Impedance Tubes ◽  
Absorption Measurements

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.

A model for the boundary condition of a porous material. Part 2

1971 ◽  
Vol 49 (2) ◽  
pp. 327-336 ◽  
Author(s):  
S. Richardson
Keyword(s):  
Boundary Condition ◽  
Porous Material ◽  
Boundary Conditions ◽  
Material Part

The present paper contains an analysis of the model of a porous material proposed in part 1, and carries out calculations which allow comparison between theory and the experiments described therein. The relevant boundary conditions to be applied at an interface between a fluid and such a material are considered.

scholarly journals Analyzing and evaluation of effective parameters on sound transmission loss of the triple-layered acoustic panels with sound-absorbing middle layer

2015 ◽  
Vol 4 (2) ◽  
pp. 250
Author(s):  
Nader Mohammadi
Keyword(s):  
Boundary Condition ◽  
Porous Material ◽  
Elastic Layer ◽  
Transmission Loss ◽  
Sound Transmission ◽  
Air Gap ◽  
Acoustic Properties ◽  
Sound Transmission Loss ◽  
Static Young’S Modulus ◽  
Wide Range

In this research, a triple-layered acoustic panel with sound-absorbing intermediate layer materials is modeled analytically in order to calculate the sound transmission loss in the normal incidence field. This information provides an appropriate platform for optimum noise control. In this paper, porous material is used as an absorbent layer between two elastic panels. In modeling these triple-layered panels, theory of wave propagation in porous materials is used and bounded boundary condition of the first elastic layer and unbounded boundary condition of the second elastic layer is applied. To validate the model, the results of this model are compared with the results of the Bolton. Comparison of results revealed very good compatibility. Here, the effect of the length of the air gap between the elastic layers, density and the material of the elastic plate, the thickness and vibro-acoustic properties of the intermediate porous material on the values of transmission loss is investigated.In a wide range of frequencies, increasing air gap, density of elastic panels and porous layer thickness, increase the transmission loss up to 10 dB. At frequencies above 10 kHz, a reduction in porosity, static Young's modulus, the loss coefficient, increasing bulk density of the solid phase, the factor of geometrical structure and viscosity of porous material, increase the sound transmission loss up to 15 dB.

scholarly journals Characterization of multi-layer porous media in an impedance tube

2021 ◽  
Vol 263 (6) ◽  
pp. 367-377
Author(s):  
Remi Roncen ◽  
Zine El Abiddine Fellah ◽  
Erick Ogam
Keyword(s):  
Porous Material ◽  
Solid Phase ◽  
Fluid Phase ◽  
Intrinsic Properties ◽  
Viscous Effects ◽  
Impedance Tube ◽  
Acoustic Methods ◽  
Impedance Tubes ◽  
Acoustic Community ◽  
Ill Posed

A porous material is the combination of a solid phase and a fluid phase, with interactions and energy exchanges between phases giving rise to the dissipation of waves traveling through the porous medium. In air, mostly viscous effects and thermal effects are responsible for dissipation, in a way that strongly depends on the pore microstructure. To evaluate the intrinsic properties pertaining to this microstructure, inverse acoustic methods have been used in the past, typically using impedance tubes to observe the way a porous sample interacts with an acoustic field. The impedance tube is a widespread tool in the acoustic community and has proven to be efficient in retrieving, via an inverse method, porous material intrinsic properties such as the porosity or the tortuosity of a sample. In this work, a Bayesian representation of knowledge is taken, where information on a material property is encoded in a probability density function. When multi-layer materials are considered, classical inverse methods become ill-posed and it might become impossible to retrieve exactly each layer's intrinsic properties. This work presents two straightforward improvements that can be used in order to lift this ill-posedness and increase the precision with which material properties are obtained.

One-Dimensional Fin-Tip Boundary Condition Correction II

2001 ◽  
Vol 22 (5) ◽  
pp. 35-40 ◽  
Author(s):  
D. C. Look Jr ◽  
Arvind Krishnan
Keyword(s):  
Boundary Condition ◽  
One Dimensional

Random pseudo promptings applied to the thermal characterization of a wet porous material

1999 ◽  
Vol 6 (1) ◽  
pp. 101-108 ◽  
Author(s):  
E. Delacre ◽  
D. Defer ◽  
E. Antczak ◽  
B. Duthoit
Keyword(s):  
Porous Material ◽  
Thermal Characterization
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