The acoustical structure of highly porous open-cell foams

Lambert, R. F.

doi:10.1121/1.388167

Cited by 22 publications

(13 citation statements)

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“…This suggests that the measurement technique to assess the strut thickness may have an important influence on the 3-parameter model outputs. Because of the difficulty to estimate the strut thickness from micrographs, it is worth mentioning that for highly porous PU foams, the scale factor B required in the 2-parameter model can be estimated from porosity measurement by inverting equation (4). In the case of foams R1-R3, this FIG.…”

Section: Resultsmentioning

confidence: 99%

“…Three types of approaches have been proposed in the literature to link microstructure properties of polyurethane foams with non-acoustic parameters and acoustic properties: (i) empirical, 3 (ii) analytical based on simplified models of the microstructure and wave propagation inside the material (also known as scaling laws), [4][5][6] and (iii) numerical homogenization derived in a representative unit-cell. [7][8][9][10][11] A detailed description of these approaches has been recently given by a) the authors.…”

Section: Introductionmentioning

confidence: 99%

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A semi-phenomenological model to predict the acoustic behavior of fully and partially reticulated polyurethane foams

Doutres¹,

Atalla²,

Dong³

2013

Journal of Applied Physics

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This paper proposes simple semi-phenomenological models to predict the sound absorption efficiency of highly porous polyurethane foams from microstructure characterization. In a previous paper [J. Appl. Phys. 110, 064901 (2011)], the authors presented a 3-parameter semi-phenomenological model linking the microstructure properties of fully and partially reticulated isotropic polyurethane foams (i.e., strut length l, strut thickness t, and reticulation rate R w ) to the macroscopic non-acoustic parameters involved in the classical Johnson-Champoux-Allard model (i.e., porosity /, airflow resistivity r, tortuosity a / , viscous K, and thermal K 0 characteristic lengths). The model was based on existing scaling laws, validated for fully reticulated polyurethane foams, and improved using both geometrical and empirical approaches to account for the presence of membrane closing the pores. This 3-parameter model is applied to six polyurethane foams in this paper and is found highly sensitive to the microstructure characterization; particularly to strut's dimensions. A simplified micro-/macro model is then presented. It is based on the cell size C s and reticulation rate R w only, assuming that the geometric ratio between strut length l and strut thickness t is known. This simplified model, called the 2-parameter model, considerably simplifies the microstructure characterization procedure. A comparison of the two proposed semi-phenomenological models is presented using six polyurethane foams being either fully or partially reticulated, isotropic or anisotropic. It is shown that the 2-parameter model is less sensitive to measurement uncertainties compared to the original model and allows a better estimation of polyurethane foams sound absorption behavior. V C 2013 American Institute of Physics. [http://dx

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A semi-phenomenological model to predict the acoustic behavior of fully and partially reticulated polyurethane foams

Doutres¹,

Atalla²,

Dong³

2013

Journal of Applied Physics

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“…In contrast to the Zwikker and Kosten method, Biot considered only the viscous effects. Subsequently, the method of Biot was extended by Lambert to include thermal effects on propagation characteristics [9] .…”

Section: Theoretical Approachmentioning

confidence: 99%

Acoustic properties of sintered FeCrAlY foams with open cells (II): Sound attenuation

Kepets

Dowling

2008

Sci. China Ser. E-Technol. Sci.

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Open-celled metal foams fabricated through metal sintering offers novel mechanical, thermal and acoustic properties. Previously, polymer foams were used as a means of absorbing acoustic energy. However, the structural applications of these foams are inherently limited. The metal sintering approach provides a cost-effective means for the mass-production of open-cell foams from a range of materials, including high-temperature steel alloys. The low Reynolds number fluid properties of sintered steel alloy (FeCrAlY) foams were investigated in a previous study. The static flow resistance of the foams was modeled based on a cylinder and a sphere arranged in a periodic lattice at general incidence to the flow, with the resulting predictions correlating well to measurements. The application of the flow resistance in an acoustic model is the primary focus of the present study. The predictions for the static flow resistance of the sintered foams are first used in a theoretical model to determine the characteristic impedances, as well as the propagation constants of the foams. Subsequently, the predicted acoustic performance of the foams is compared to experimental results. Finally, the design space for a simple acoustic absorber incorporating sintered foams is examined, with the effects of absorber size, foam selection, and foam spacing explored. metal foam, sound absorption, modeling, experiment, acoustic design

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“…͑4͒ shall be solved by using the proper boundary condition on the fibers. In the literature [1][2][3][4][5][6][7][8][9][10][11][12] one assumes that the temperature rise on the fibers is zero. But this is not accurate for light commercial glass wool, because the heat capacity of the glass fibers per volume is not infinitely great compared to the heat capacity of the air.…”

Section: General Theorymentioning

confidence: 99%

“…The established way of predicting the acoustical properties of fiber materials is by use of the theory of porous materials, which has been described by many authors. [1][2][3][4][5][6][7][8][9][10][11][12] In this theory, one assumes that the material consists of a matrix with circular pores of small radius. The compressibility of the air in the pores can be computed if one knows the radius of the pores, but for fibrous material it is not obvious how one finds the radius of the pores from the diameters of the fibers and their mean distances.…”

Section: Introductionmentioning

confidence: 99%

Compressibility of air in fibrous materials

Tarnow

1996

The Journal of the Acoustical Society of America

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The dynamic compressibility of air in fibrous materials has been computed for two assumed configurations of fibers which are close to the geometry of real fiber materials. Models with parallel cylinders placed in a regular square lattice and placed randomly are treated. For these models the compressibility is computed approximately from the diameter and mean distances between cylinders. This requires calculation of the air temperature, which is calculated for cylinders in a regular lattice by the Wigner-Seitz cell approximation. In the case of random placement, the calculation is done by a summation over thermal waves from all fibers, and by a self-consistent procedure. Figures of the compressibility in the frequency range 10-100 000 Hz, are given for diameter of the cylinders of 6.8 m, and mean distances between them from 50 to 110 m, which corresponds to glass wool with a density of 40 to 16 kg/m 3 . When the theoretical values for random placement were compared with measurements, it turned out that the random model could not describe the experimental data. However, they could be described accurately by assuming that the fibers have a tendency to form pairs.

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The acoustical structure of highly porous open-cell foams

Cited by 22 publications

References 0 publications

A semi-phenomenological model to predict the acoustic behavior of fully and partially reticulated polyurethane foams

A semi-phenomenological model to predict the acoustic behavior of fully and partially reticulated polyurethane foams

Acoustic properties of sintered FeCrAlY foams with open cells (II): Sound attenuation

Compressibility of air in fibrous materials

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