Numerical investigation of active porous composites with enhanced acoustic absorption

Zieliński, Tomasz G.

doi:10.1016/j.jsv.2011.05.029

Cited by 22 publications

(15 citation statements)

References 34 publications

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“…at 0.9 kHz and 1.8 kHz) acoustic resonances resulting from the motion of elastic skeleton of the soft PU foam are visible; at higher frequencies the skeleton behaviour tends to be rigid even for the soft PU foam. This is a typical situation for soft PU foams: the low-frequency resonances and anti-resonances of elastic skeleton significantly influence sound propagation and absorption; the flexibility of elastic skeleton may also be utilized in order to improve the acoustic absorption in semi-active (Zielinski, Rak, 2010) or active way (Zielinski, 2008;2010;2011). The sound absorption properties of PU foams may also be improved passively by changing the skeleton density and stiffness -this can be attained by adding some inclusions in the foam matrix, for example, rice hull (Wang et al, 2013), or tea-leaf-fibres (Ekici, 2012).…”

Section: Discussion Of the Resultsmentioning

confidence: 99%

Acoustic Absorption of a New Class of Alumina Foams with Various High-Porosity Levels

Zieliński¹,

Potoczek²,

Śliwa³

et al. 2013

Archives of Acoustics

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Recently, a new class of ceramic foams with porosity levels up to 90% has been developed as a result of the association of the gelcasting process and aeration of the ceramic suspension. This paper presents and discusses original results advertising sound absorbing capabilities of such foams. The authors manufactured three types of alumina foams in order to investigate three porosity levels, namely: 72, 88, and 90%. The microstructure of foams was examined and typical dimensions and average sizes of cells (pores) and cell-linking windows were found for each porosity case. Then, the acoustic absorption coefficient was measured in a wide frequency range for several samples of various thickness cut out from the foams. The results were discussed and compared with the acoustic absorption of typical polyurethane foams proving that the alumina foams with high porosity of 88-90% have excellent sound absorbing properties competitive with the quality of sound absorbing PU foams of higher porosity.

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Section: Discussion Of the Resultsmentioning

confidence: 99%

Acoustic Absorption of a New Class of Alumina Foams with Various High-Porosity Levels

Zieliński¹,

Potoczek²,

Śliwa³

et al. 2013

Archives of Acoustics

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“…II A. Whatever the case, when the surface acoustic impedance of a two-layered (17) or single-layer medium (18) is known, the complex-valued reflection coefficient R and the real-valued acoustic absorption coefficient A can be calculated 12,16 as…”

Section: Modeling the Acoustic Impedance And Absorption Of Porousmentioning

confidence: 99%

“…The poroelastic model for sound absorbing media must be used when the vibrations of the solid frame cannot be neglected, for example, in the case of soft porous media or in active systems involving porous materials. [14][15][16] The essential parameters of the Johnson-Allard (JCA, JCAL, or JCAPL) and Biot-Allard models which result from the micro-geometry of the solid frame are in fact some sort of macroscopic, average geometric characteristics of the porous medium derived on the basis of homogenization theory. Although, they can be measured directly (see, for example, Refs.…”

Section: Introductionmentioning

confidence: 99%

Normalized inverse characterization of sound absorbing rigid porous media

Zieliński

2015

The Journal of the Acoustical Society of America

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This paper presents a methodology for the inverse characterization of sound absorbing rigid porous media, based on standard measurements of the surface acoustic impedance of a porous sample. The model parameters need to be normalized to have a robust identification procedure which fits the model-predicted impedance curves with the measured ones. Such a normalization provides a substitute set of dimensionless (normalized) parameters unambiguously related to the original model parameters. Moreover, two scaling frequencies are introduced, however, they are not additional parameters and for different, yet reasonable, assumptions of their values, the identification procedure should eventually lead to the same solution. The proposed identification technique uses measured and computed impedance curves for a porous sample not only in the standard configuration, that is, set to the rigid termination piston in an impedance tube, but also with air gaps of known thicknesses between the sample and the piston. Therefore, all necessary analytical formulas for sound propagation in double-layered media are provided. The methodology is illustrated by one numerical test and by two examples based on the experimental measurements of the acoustic impedance and absorption of porous ceramic samples of different thicknesses and a sample of polyurethane foam.

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“…Basing on the results of surface acoustic impedance the acoustic absorption coefficient AðxÞ was computed using the following formulas: 21,40 A…”

Section: Surface Acoustic Impedance and Absorption For Rigid Foam mentioning

confidence: 99%

Generation of random microstructures and prediction of sound velocity and absorption for open foams with spherical pores

Zieliński¹

2015

The Journal of the Acoustical Society of America

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This paper proposes and discusses an approach for the design and quality inspection of the morphology dedicated for sound absorbing foams, using a relatively simple technique for a random generation of periodic microstructures representative for open-cell foams with spherical pores. The design is controlled by a few parameters, namely, the total open porosity and the average pore size, as well as the standard deviation of pore size. These design parameters are set up exactly and independently, however, the setting of the standard deviation of pore sizes requires some number of pores in the representative volume element (RVE); this number is a procedure parameter. Another pore structure parameter which may be indirectly affected is the average size of windows linking the pores, however, it is in fact weakly controlled by the maximal pore-penetration factor, and moreover, it depends on the porosity and pore size. The proposed methodology for testing microstructure-designs of sound absorbing porous media applies the multi-scale modeling where some important transport parameters-responsible for sound propagation in a porous medium-are calculated from microstructure using the generated RVE, in order to estimate the sound velocity and absorption of such a designed material.

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Numerical investigation of active porous composites with enhanced acoustic absorption

Cited by 22 publications

References 34 publications

Acoustic Absorption of a New Class of Alumina Foams with Various High-Porosity Levels

Acoustic Absorption of a New Class of Alumina Foams with Various High-Porosity Levels

Normalized inverse characterization of sound absorbing rigid porous media

Generation of random microstructures and prediction of sound velocity and absorption for open foams with spherical pores

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