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Zieliński T.G., Opiela K.C., Dauchez N.♦, Boutin T.♦, Galland M.-A.♦, Attenborough K.♦, Extremely tortuous sound absorbers with labyrinthine channels in non-porous and microporous solid skeletons,
APPLIED ACOUSTICS, ISSN: 0003-682X, DOI: 10.1016/j.apacoust.2023.109816, Vol.217, pp.109816-1-13, 2024Abstract: An assembly of additively-manufactured modules to form two-dimensional networks of labyrinthine slits results in a sound absorber with extremely high tortuosity and thereby a relatively low frequency quarter wavelength resonance. Fully analytical modelling is developed for the generic design of such composite acoustic panels, allowing rapid exploration of various specific designs. In addition to labyrinthine channels in a non-porous solid skeleton, a case is also considered where the skeleton has microporosity such that its permeability is very much lower than that due to the labyrinthine channels alone. The analytical modelling is verified by numerical calculations, as well as sound absorption measurements performed on several 3D printed samples of modular composite panels. The experimental validation required overcoming the non-trivial difficulties related to additive manufacturing and testing samples of extreme tortuosity. However, due to the two-dimensionality and modularity of the proposed design, such absorbers can possibly be produced without 3D printing by assembling simple, identical modules produced separately. The experimental results fully confirmed the theoretical predictions that significant sound absorption, almost perfect at the peak, can be achieved at relatively low frequencies using very thin panels, especially those with double porosity. Keywords: Sound absorption,Extreme tortuosity,Double porosity,Acoustic composites,Additive manufacturing Affiliations:
Zieliński T.G. | - | IPPT PAN | Opiela K.C. | - | IPPT PAN | Dauchez N. | - | Sorbonne University Alliance (FR) | Boutin T. | - | Sorbonne University Alliance (FR) | Galland M.-A. | - | École Centrale de Lyon (FR) | Attenborough K. | - | The Open University (GB) |
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Opiela K.C., Zieliński T.G., Attenborough K.♦, Limitations on validating slitted sound absorber designs through budget additive manufacturing,
Materials & Design, ISSN: 0264-1275, DOI: 10.1016/j.matdes.2022.110703, Vol.218, pp.110703-1-17, 2022Abstract: The potential usefulness of relatively simple pore microstructures such as parallel, identical, inclined slits for creating broadband sound absorption has been argued through analytical models. In principle, such microstructures could be realised through budget additive manufacturing. However, validation of the analytical predictions through normal incidence impedance tube measurements on finite layers is made difficult by the finite size of the tube. The tube walls curtail the lengths of inclined slits and, as a result, prevent penetration of sound through the layer. As well as demonstrating and modelling this effect, this paper explores two manufacturing solutions. While analytical and numerical predictions correspond well to absorption spectra measured on slits normal to the surface, discrepancies between measured and predicted sound absorption are noticed for perforated and zigzag slit configurations. For perforated microgeometries this is found to be the case with both numerical and analytical modelling based on variable length dead-end pores. Discrepancies are to be expected since the dead-end pore model does not allow for narrow pores in which viscous effects are important. For zigzag slits it is found possible to modify the permeability used in the inclined slit analytical model empirically to obtain reasonable agreement with data. Keywords: slitted sound absorber, additive manufacturing, microstructure-based modelling Affiliations:
Opiela K.C. | - | IPPT PAN | Zieliński T.G. | - | IPPT PAN | Attenborough K. | - | The Open University (GB) |
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Zieliński T.G., Venegas R.♦, Perrot C.♦, Červenka M.♦, Chevillotte F.♦, Attenborough K.♦, Benchmarks for microstructure-based modelling of sound absorbing rigid-frame porous media,
JOURNAL OF SOUND AND VIBRATION, ISSN: 0022-460X, DOI: 10.1016/j.jsv.2020.115441, Vol.483, pp.115441-1-38, 2020Abstract: This work presents benchmark examples related to the modelling of sound absorbing porous media with rigid frame based on the periodic geometry of their microstructures. To this end, rigorous mathematical derivations are recalled to provide all necessary equations, useful relations, and formulae for the so-called direct multi-scale computations, as well as for the hybrid multi-scale calculations based on the numerically determined transport parameters of porous materials. The results of such direct and hybrid multi-scale calculations are not only cross verified, but also confirmed by direct numerical simulations based on the linearised Navier-Stokes-Fourier equations. In addition, relevant theoretical and numerical issues are discussed, and some practical hints are given. Keywords: porous media, periodic microstructure, wave propagation, sound absorption Affiliations:
Zieliński T.G. | - | IPPT PAN | Venegas R. | - | MATELYS – Research Lab (FR) | Perrot C. | - | other affiliation | Červenka M. | - | Czech Technical University in Prague (CZ) | Chevillotte F. | - | MATELYS – Research Lab (FR) | Attenborough K. | - | The Open University (GB) |
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Aygün H.♦, Attenborough K.♦, Postema M.♦, A review of the state of art in applying Biot theory to acoustic propagation through the bone,
Open Access Library Journal, ISSN: 2333-9705, DOI: 10.4236/oalib.1100994, Vol.e994, pp.1-12, 2014Abstract: Understanding the propagation of acoustic waves through a liquid-perfused porous solid frame- work such as cancellous bone is an important pre-requisite to improve the diagnosis of osteoporosis by ultrasound. In order to elucidate the propagation dependence upon the material and structural properties of cancellous bone, several theoretical models have been considered to date, with Biot-based models demonstrating the greatest potential. This paper describes the fundamental basis of these models and reviews their performance. Keywords: Acoustic, Propagation, Bone, Theoretical Model Affiliations:
Aygün H. | - | Southampton Solent University (GB) | Attenborough K. | - | The Open University (GB) | Postema M. | - | other affiliation |
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Aygün H.♦, Attenborough K.♦, Postema M.♦, Lauriks W.♦, Langton Ch.M.♦, Predictions of angle dependent tortuosity and elasticity effects on sound propagation in cancellous bone,
JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, ISSN: 0001-4966, DOI: 10.1121/1.3242358, Vol.126, No.6, pp.3286-3290, 2009Abstract: The anisotropic pore structure and elasticity of cancellous bone cause wave speeds and attenuation in cancellous bone to vary with angle. Previously published predictions of the variation in wave speed with angle are reviewed. Predictions that allow tortuosity to be angle dependent but assume isotropic elasticity compare well with available data on wave speeds at large angles but less well for small angles near the normal to the trabeculae. Claims for predictions that only include angle-dependence in elasticity are found to be misleading. Audio-frequency data obtained at audio-frequencies in air-filled bone replicas are used to derive an empirical expression for the angle-and porosity-dependence of tortuosity. Predictions that allow for either angle dependent tortuosity or angle dependent elasticity or both are compared with existing data for all angles and porosities. Affiliations:
Aygün H. | - | Southampton Solent University (GB) | Attenborough K. | - | The Open University (GB) | Postema M. | - | other affiliation | Lauriks W. | - | other affiliation | Langton Ch.M. | - | other affiliation |
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