Jieun Yang
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1
Wave diffraction is typically regarded as a limiting factor in the performance of acoustic noise barriers, enabling sound to bend over finite structures and reducing attenuation, particularly at low frequencies. In this work, we demonstrate that diffraction can instead be harnessed as a functional mechanism for sound suppression by designing metamaterial barriers that incorporate a vertical array of resonators along the barrier surface. The proposed structure changes the dispersion characteristics of edge-diffracted waves and acts as a boundary that transforms diffraction into surface-guided wave propagation. Our analysis reveals that the metabarrier achieves broadband sound attenuation through two distinct mechanisms: (i) the formation of strong standing wave modes due to surface-guided waves confined along the barrier face, and (ii) resonance-induced evanescence decay resulting in localized band gap formation. Together, these effects lead to a substantial enhancement in insertion loss over a broad frequency range. Furthermore, we show that performance can be tuned by implementing double-sided arrays. These findings introduce a new framework for acoustic wave control, in which diffraction is not merely mitigated but actively exploited as a design-enabling feature.
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Wave diffraction is typically regarded as a limiting factor in the performance of acoustic noise barriers, enabling sound to bend over finite structures and reducing attenuation, particularly at low frequencies. In this work, we demonstrate that diffraction can instead be harnessed as a functional mechanism for sound suppression by designing metamaterial barriers that incorporate a vertical array of resonators along the barrier surface. The proposed structure changes the dispersion characteristics of edge-diffracted waves and acts as a boundary that transforms diffraction into surface-guided wave propagation. Our analysis reveals that the metabarrier achieves broadband sound attenuation through two distinct mechanisms: (i) the formation of strong standing wave modes due to surface-guided waves confined along the barrier face, and (ii) resonance-induced evanescence decay resulting in localized band gap formation. Together, these effects lead to a substantial enhancement in insertion loss over a broad frequency range. Furthermore, we show that performance can be tuned by implementing double-sided arrays. These findings introduce a new framework for acoustic wave control, in which diffraction is not merely mitigated but actively exploited as a design-enabling feature.
Journal article
(2025)
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Baltazar Briere de La Hosseraye, Jieun Yang, Maarten Hornikx
The in situ measurement of acoustic surfaces presents a significant challenge in room acoustics, as it is often impractical to conduct laboratory measurements of already installed materials. In a former study, the in situ analysis of porous samples that react locally when supported by a solid wall demonstrated a good degree of accuracy. Nevertheless, when a porous layer is supported by a large air cavity (depth >100 mm), a situation commonly seen in suspended ceiling designs, the air cavity exhibits a non-locally reacting behavior; thus, the local reaction cannot be reliably assumed. This study introduces a method to characterize such a non-locally responding system through in situ PU probe measurements, utilizing an inverse technique to fit the parameters of the impedance model of a porous layer that is backed by an infinite air layer, based on the measured reflection coefficient. The precision of the approach was confirmed through 2D numerical simulations, indicating that the method produced reliable results for air cavities of 200 mm or deeper. The method was then experimentally validated on systems comprising several porous layers supported by air cavities of varying depths. Good agreement was obtained between the parameters measured experimentally using the proposed technique and the references, even in cases where the air cavity was less than 200 mm deep. Additionally, the proposed method demonstrated more precise characterization results compared to those achieved by fitting the parameters of an impedance model based on a standard multilayer model.
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The in situ measurement of acoustic surfaces presents a significant challenge in room acoustics, as it is often impractical to conduct laboratory measurements of already installed materials. In a former study, the in situ analysis of porous samples that react locally when supported by a solid wall demonstrated a good degree of accuracy. Nevertheless, when a porous layer is supported by a large air cavity (depth >100 mm), a situation commonly seen in suspended ceiling designs, the air cavity exhibits a non-locally reacting behavior; thus, the local reaction cannot be reliably assumed. This study introduces a method to characterize such a non-locally responding system through in situ PU probe measurements, utilizing an inverse technique to fit the parameters of the impedance model of a porous layer that is backed by an infinite air layer, based on the measured reflection coefficient. The precision of the approach was confirmed through 2D numerical simulations, indicating that the method produced reliable results for air cavities of 200 mm or deeper. The method was then experimentally validated on systems comprising several porous layers supported by air cavities of varying depths. Good agreement was obtained between the parameters measured experimentally using the proposed technique and the references, even in cases where the air cavity was less than 200 mm deep. Additionally, the proposed method demonstrated more precise characterization results compared to those achieved by fitting the parameters of an impedance model based on a standard multilayer model.
The acoustic absorption of a porous structure within a specific frequency range can be tuned by varying its porosity along its thickness. In this work, triply periodic minimal surfaces (TPMS) are employed to generate graded porous structures, where the continuous porosity gradient is controlled by a mathematical function involving geometric parameters. A hybrid homogenization technique, combined with the transfer matrix method (TMM), is used to predict the normal incidence absorption coefficient of the graded TPMS structure. The porosity distribution along the thickness is then optimized using a global search method combined with a local gradient-based solver to maximize acoustic absorption within a target frequency range. The optimization results suggest that a combination of high- and low-porosity layers achieves broadband impedance matching conditions by shifting the so-called quarter-wavelength resonance frequencies. The design of the TPMS absorbers is validated through impedance tube measurements of 3D-printed samples.
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The acoustic absorption of a porous structure within a specific frequency range can be tuned by varying its porosity along its thickness. In this work, triply periodic minimal surfaces (TPMS) are employed to generate graded porous structures, where the continuous porosity gradient is controlled by a mathematical function involving geometric parameters. A hybrid homogenization technique, combined with the transfer matrix method (TMM), is used to predict the normal incidence absorption coefficient of the graded TPMS structure. The porosity distribution along the thickness is then optimized using a global search method combined with a local gradient-based solver to maximize acoustic absorption within a target frequency range. The optimization results suggest that a combination of high- and low-porosity layers achieves broadband impedance matching conditions by shifting the so-called quarter-wavelength resonance frequencies. The design of the TPMS absorbers is validated through impedance tube measurements of 3D-printed samples.
Journal article
(2025)
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Sara Mouman, Yao Koutsawa, Lucas Binsfeld, Levent Kirkayak, Jieun Yang, Gaetano Giunta
This work presents a comparative study on the mechanical homogenisation of Triply Periodic Minimal Surface (TPMS) lattice structures in the linear elastic regime, which have attracted significant interest for their unique ability to combine lightweight design with tailored properties. The study investigates the effective mechanical behaviour of Representative Unit Cells (RUCs) generated using the open-source Python tool Microgen. Two homogenisation strategies are considered: (i) Finite Element (FE)-based homogenisation carried out in Abaqus, and (ii) the Mechanics of Structure Genome (MSG), a unified theory for multi-scale constitutive modelling, implemented in an in-house software tool. The comparison encompasses multiple TPMS topologies, including well-studied cases used for validation, namely gyroid and diamond, as well as less-explored ones, such as PMY and F-Rhombic Dodecahedron, to provide new insights. RUCs are analysed across relative densities ranging from 10 to 50%. Equivalent linear elastic properties (Young’s moduli, shear moduli, and Poisson’s ratios) are derived and compared to assess the consistency, accuracy, and computational efficiency of the two approaches. The results show that both methods yield effective properties with less than 1% difference between them, and less than 5% deviation from experimental data reported in the literature for the effective Young’s modulus. Furthermore, the anisotropy of each TPMS topology across the range of relative densities is examined through the directional distribution of Young’s moduli. The outcomes are expected to clarify the strengths and limitations of FE versus MSG in capturing the effective behaviour of architected cellular solids, thus supporting the selection of homogenisation strategies for the design of lattice-based lightweight structures.
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This work presents a comparative study on the mechanical homogenisation of Triply Periodic Minimal Surface (TPMS) lattice structures in the linear elastic regime, which have attracted significant interest for their unique ability to combine lightweight design with tailored properties. The study investigates the effective mechanical behaviour of Representative Unit Cells (RUCs) generated using the open-source Python tool Microgen. Two homogenisation strategies are considered: (i) Finite Element (FE)-based homogenisation carried out in Abaqus, and (ii) the Mechanics of Structure Genome (MSG), a unified theory for multi-scale constitutive modelling, implemented in an in-house software tool. The comparison encompasses multiple TPMS topologies, including well-studied cases used for validation, namely gyroid and diamond, as well as less-explored ones, such as PMY and F-Rhombic Dodecahedron, to provide new insights. RUCs are analysed across relative densities ranging from 10 to 50%. Equivalent linear elastic properties (Young’s moduli, shear moduli, and Poisson’s ratios) are derived and compared to assess the consistency, accuracy, and computational efficiency of the two approaches. The results show that both methods yield effective properties with less than 1% difference between them, and less than 5% deviation from experimental data reported in the literature for the effective Young’s modulus. Furthermore, the anisotropy of each TPMS topology across the range of relative densities is examined through the directional distribution of Young’s moduli. The outcomes are expected to clarify the strengths and limitations of FE versus MSG in capturing the effective behaviour of architected cellular solids, thus supporting the selection of homogenisation strategies for the design of lattice-based lightweight structures.
This study presents numerical solutions for two vibroacoustic problems using the time-domain nodal discontinuous Galerkin (DG) method. The first problem is the impact sound radiation from a rectangular slab into a cuboid room, and the second is the sound transmission between two cuboid rooms with direct and flanking contributions. The structures are modelled as a three-dimensional solid governed by the linear elasticity equations, and sound propagation in the rooms is governed by the linear acoustic equations. In the impact sound radiation case, the normalised sound pressure is evaluated and compared to the one obtained by the modal expansion method. In the sound transmission case, pressure transfer functions between different positions are calculated and compared to those obtained by the finite element method (FEM). The upwind numerical fluxes in DG for both governing equations, as well as the coupling conditions, are presented. There is excellent agreement between the solutions obtained by the nodal DG and those obtained by the modal expansion method/FEM. Although minor discrepancies exist in the resonance frequencies and magnitude, the overall trend shows good agreement.
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This study presents numerical solutions for two vibroacoustic problems using the time-domain nodal discontinuous Galerkin (DG) method. The first problem is the impact sound radiation from a rectangular slab into a cuboid room, and the second is the sound transmission between two cuboid rooms with direct and flanking contributions. The structures are modelled as a three-dimensional solid governed by the linear elasticity equations, and sound propagation in the rooms is governed by the linear acoustic equations. In the impact sound radiation case, the normalised sound pressure is evaluated and compared to the one obtained by the modal expansion method. In the sound transmission case, pressure transfer functions between different positions are calculated and compared to those obtained by the finite element method (FEM). The upwind numerical fluxes in DG for both governing equations, as well as the coupling conditions, are presented. There is excellent agreement between the solutions obtained by the nodal DG and those obtained by the modal expansion method/FEM. Although minor discrepancies exist in the resonance frequencies and magnitude, the overall trend shows good agreement.
Journal article
(2024)
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Indra Sihar, Jieun Yang, Maarten Hornikx
In this work, the vibrations of a structure excited by an impact source are modelled using the time domain nodal discontinuous Galerkin (DG) method, which solves linear elasticity equations. A scaled lightweight wooden floor (LWF) structure which consists of components that differ in their mechanical properties is taken as a case study. The Rankine-Hugoniot jump conditions for piece-wise constant material properties are used to obtain accurate numerical fluxes in the DG method, and their detailed derivation is the main contribution of this work. Free boundary conditions are applied on the surface of the structures, and constant viscous damping force is added to the model to have vibrational energy losses. To validate the numerical results, the mobility of the structure is calculated and compared with experimental data. The agreement is good regarding the natural frequencies, with a maximum absolute difference of less than 11 Hz in the frequency range below 200 Hz. The adopted damping approach is shown to be insufficient to represent a broad frequency range.
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In this work, the vibrations of a structure excited by an impact source are modelled using the time domain nodal discontinuous Galerkin (DG) method, which solves linear elasticity equations. A scaled lightweight wooden floor (LWF) structure which consists of components that differ in their mechanical properties is taken as a case study. The Rankine-Hugoniot jump conditions for piece-wise constant material properties are used to obtain accurate numerical fluxes in the DG method, and their detailed derivation is the main contribution of this work. Free boundary conditions are applied on the surface of the structures, and constant viscous damping force is added to the model to have vibrational energy losses. To validate the numerical results, the mobility of the structure is calculated and compared with experimental data. The agreement is good regarding the natural frequencies, with a maximum absolute difference of less than 11 Hz in the frequency range below 200 Hz. The adopted damping approach is shown to be insufficient to represent a broad frequency range.
Journal article
(2024)
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Baltazar Briere de La Hosseraye, Jieun Yang, Maarten Hornikx
The in situ characterization of materials is a crucial challenge in room acoustics, as laboratories measurement cannot always be applied in consultancy practices. In particular, there is a lack of method to characterize in situ systems with perforated facings, which are commonly encountered systems in room acoustics. In this paper, the in situ characterization of a rigidly-backed porous material behind a rigid perforated facing by means of pressure–velocity measurements is presented. The method includes an inverse impedance model fitting based on measurement in a limited frequency range. The applicability of this method was studied by measuring a variety of perforated facings, whether in front of an air cavity or backed by a porous layer, and comparing the obtained impedance model parameters to reference values. Good agreement was observed between the retrieved parameters and the references, with the errors in all retrieved parameters moving mass, facing thickness, cavity depth, porous layer thickness and porous layer flow resistivity not exceeding 15%.
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The in situ characterization of materials is a crucial challenge in room acoustics, as laboratories measurement cannot always be applied in consultancy practices. In particular, there is a lack of method to characterize in situ systems with perforated facings, which are commonly encountered systems in room acoustics. In this paper, the in situ characterization of a rigidly-backed porous material behind a rigid perforated facing by means of pressure–velocity measurements is presented. The method includes an inverse impedance model fitting based on measurement in a limited frequency range. The applicability of this method was studied by measuring a variety of perforated facings, whether in front of an air cavity or backed by a porous layer, and comparing the obtained impedance model parameters to reference values. Good agreement was observed between the retrieved parameters and the references, with the errors in all retrieved parameters moving mass, facing thickness, cavity depth, porous layer thickness and porous layer flow resistivity not exceeding 15%.
Conference paper
(2023)
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X. Guan, J. Yang, Elke Deckers, Maarten Hornikx
Triply periodic minimal surfaces (TPMS), a class of periodic implicit surface with zero mean curvature, are emerging as an excellent solution to create graded porous structures. The grading of a porous layer can enhance and broaden the acoustic absorption in a target frequency range. The porosity gradient within the TPMS structure can be precisely controlled by a mathematical function, straightforwardly allowing for optimization towards the desired absorption. As the first step of the optimization procedure, we present a computational approach to determine acoustic absorption properties of functionally graded TPMS porous structures: the transport parameters of a rigid-frame homogeneous TPMS porous absorber are found by the finite element simulations of three static problems, then the absorption coefficient of the TPMS porous structure with graded porosity along the thickness is calculated with the transfer matrix method. The presented approach is validated by direct numerical simula- tions of the same porous structure.
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Triply periodic minimal surfaces (TPMS), a class of periodic implicit surface with zero mean curvature, are emerging as an excellent solution to create graded porous structures. The grading of a porous layer can enhance and broaden the acoustic absorption in a target frequency range. The porosity gradient within the TPMS structure can be precisely controlled by a mathematical function, straightforwardly allowing for optimization towards the desired absorption. As the first step of the optimization procedure, we present a computational approach to determine acoustic absorption properties of functionally graded TPMS porous structures: the transport parameters of a rigid-frame homogeneous TPMS porous absorber are found by the finite element simulations of three static problems, then the absorption coefficient of the TPMS porous structure with graded porosity along the thickness is calculated with the transfer matrix method. The presented approach is validated by direct numerical simula- tions of the same porous structure.
Conference paper
(2022)
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Lingge Tan, Jieun Yang, Jian Kang, Hongpeng Xu
Diffusive surfaces can be optimally designed for both acoustic and aesthetic purposes. Adapting to the parametric demands of interface design, fractals are widely applied as a fusion of mathematical calculation and artistic design. The Sierpinski triangle is a self-similar structure with a more impressive appearance than conventional acoustic diffusers. However, the acoustic performance of Sierpinski fractal patterns has not been considered. This paper proposes a design of an acoustic diffuser based on the construction rules of the Sierpinski triangle to broaden the effective frequency range. The diffuser is made of triangular blocks of different sizes attached to a plane surface. A series of case studies are examined through numerical simulations based on the boundary element method (BEM) to investigate the effects of the number of iterations, the randomness of block arrangements, and the inclination of block tops. The diffusion performance of a conventional quadratic residue diffuser (QRD) is compared to confirm the advantage of the designed diffuser for broadening the effective frequency range. Furthermore, a workflow of the design and evaluation processes is presented to fabricate samples that could be used to tune the design parameters according to their in-field application demands.
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Diffusive surfaces can be optimally designed for both acoustic and aesthetic purposes. Adapting to the parametric demands of interface design, fractals are widely applied as a fusion of mathematical calculation and artistic design. The Sierpinski triangle is a self-similar structure with a more impressive appearance than conventional acoustic diffusers. However, the acoustic performance of Sierpinski fractal patterns has not been considered. This paper proposes a design of an acoustic diffuser based on the construction rules of the Sierpinski triangle to broaden the effective frequency range. The diffuser is made of triangular blocks of different sizes attached to a plane surface. A series of case studies are examined through numerical simulations based on the boundary element method (BEM) to investigate the effects of the number of iterations, the randomness of block arrangements, and the inclination of block tops. The diffusion performance of a conventional quadratic residue diffuser (QRD) is compared to confirm the advantage of the designed diffuser for broadening the effective frequency range. Furthermore, a workflow of the design and evaluation processes is presented to fabricate samples that could be used to tune the design parameters according to their in-field application demands.
Conference paper
(2022)
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Baltazar Briere de La Hosseraye, Jieun Yang, Maarten Hornikx
Journal article
(2022)
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Baltazar Briere de La Hosseraye, Maarten Hornikx, Jieun Yang
Reliable data on acoustical properties of materials are crucial for the design of a desired acoustic environment as well as to obtain accurate results from acoustic simulations. Although the acoustical properties of materials can be obtained via laboratory measurements, situations where in situ measurements are needed are often encountered. However, in situ measurement methods presented so far are limited by their poor portability or inaccuracies in the low-frequency range. In this work, we propose a characterization method that combines an in situ pressure-velocity (PU) measurement with a model fitting procedure using the Delany-Bazley-Miki impedance model for porous materials. The method uses an optimization routine to find the best match of measured and modelled reflection coefficient values within a given frequency range for the optimization parameters: flow resistivity, panel thickness, and probe-sample distance. The optimal parameter values allow, in turn, calculating the porous panel’s reflection coefficients for a broad frequency range including frequencies below the lower bounds of the optimization frequency range. The sensitivity of the method to panel width, lower bound of fitting frequency range, and to excluding parasitic reflections by time windowing is studied. The study shows that the proposed method provides characterization results in good agreement with reference data for panels of dimensions larger than 1800 mm and that the method is robust for reduction of one dimension of the panel down to 300 mm. It also shows that the model fitting accuracy is best when the frequency range of analysis is restricted to 1000–5000 Hz.
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Reliable data on acoustical properties of materials are crucial for the design of a desired acoustic environment as well as to obtain accurate results from acoustic simulations. Although the acoustical properties of materials can be obtained via laboratory measurements, situations where in situ measurements are needed are often encountered. However, in situ measurement methods presented so far are limited by their poor portability or inaccuracies in the low-frequency range. In this work, we propose a characterization method that combines an in situ pressure-velocity (PU) measurement with a model fitting procedure using the Delany-Bazley-Miki impedance model for porous materials. The method uses an optimization routine to find the best match of measured and modelled reflection coefficient values within a given frequency range for the optimization parameters: flow resistivity, panel thickness, and probe-sample distance. The optimal parameter values allow, in turn, calculating the porous panel’s reflection coefficients for a broad frequency range including frequencies below the lower bounds of the optimization frequency range. The sensitivity of the method to panel width, lower bound of fitting frequency range, and to excluding parasitic reflections by time windowing is studied. The study shows that the proposed method provides characterization results in good agreement with reference data for panels of dimensions larger than 1800 mm and that the method is robust for reduction of one dimension of the panel down to 300 mm. It also shows that the model fitting accuracy is best when the frequency range of analysis is restricted to 1000–5000 Hz.
Journal article
(2022)
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Lingge Tan, Jieun Yang, Jian Kang, Hongpeng Xu
This paper proposes a new design of an acoustic diffuser based on the construction rules of the Sierpinski triangle in order to broaden the effective diffusion frequency range. The diffuser is made of triangular blocks of different sizes attached to a plane surface. The effects of the number of fractal iterations, the height of triangular blocks, and arrangements of the blocks on the normal-incidence diffusion coefficients in the near field are examined through numerical simulations based on the boundary element method (BEM) in the frequency range of 100 Hz – 5 kHz. Furthermore, measurement results will be presented to validate the diffusion performance presented by the numerical simulations. The diffusion performance of a conventional quadratic residue diffuser (QRD) is compared to confirm the advantage of the designed diffuser for broadening the effective frequency range. It shows that the fractal patterns with various sizes of blocks improve diffusion performance compared to the conventional QRD of the same size, especially in the mid-low frequency range below 1 kHz.
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This paper proposes a new design of an acoustic diffuser based on the construction rules of the Sierpinski triangle in order to broaden the effective diffusion frequency range. The diffuser is made of triangular blocks of different sizes attached to a plane surface. The effects of the number of fractal iterations, the height of triangular blocks, and arrangements of the blocks on the normal-incidence diffusion coefficients in the near field are examined through numerical simulations based on the boundary element method (BEM) in the frequency range of 100 Hz – 5 kHz. Furthermore, measurement results will be presented to validate the diffusion performance presented by the numerical simulations. The diffusion performance of a conventional quadratic residue diffuser (QRD) is compared to confirm the advantage of the designed diffuser for broadening the effective frequency range. It shows that the fractal patterns with various sizes of blocks improve diffusion performance compared to the conventional QRD of the same size, especially in the mid-low frequency range below 1 kHz.
Conference paper
(2021)
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Jieun Yang, Maarten Hornikx
Conference paper
(2021)
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Indra Sihar, Jieun Yang, Maarten Hornikx
Conference paper
(2021)
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Baltazar Briere de La Hosseraye, Jieun Yang, Maarten Hornikx
Journal article
(2020)
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Tomasz Zieliński, Kamil Opiela, Rafał Wróbel, Seok Kim, Shahrzad Ghaffari Mosanenzadeh, Nicholas X. Fang, Jieun Yang, Baltazar Briere de La Hosseraye, Maarten Hornikx, Edouard Salze, Marie-Annick Galland, René Boonen, Piotr Pawłowski, Augusto Carvalho de Sousa, Elke Deckers, Mathieu Gaborit, Jean-Philippe Groby, Nicolas Dauchez, Thomas Boutin, John Kennedy, Daniel Trimble, Henry Rice, Bart Van Damme, Gwenael Hannema
The purpose of this work is to check if additive manufacturing technologies are suitable for reproducing porous samples designed for sound absorption. The work is an inter-laboratory test, in which the production of samples and their acoustic measurements are carried out independently by different laboratories, sharing only the same geometry codes describing agreed periodic cellular designs. Different additive manufacturing technologies and equipment are used to make samples. Although most of the results obtained from measurements performed on samples with the same cellular design are very close, it is shown that some discrepancies are due to shape and surface imperfections, or microporosity, induced by the manufacturing process. The proposed periodic cellular designs can be easily reproduced and are suitable for further benchmarking of additive manufacturing techniques for rapid prototyping of acoustic materials and metamaterials.
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The purpose of this work is to check if additive manufacturing technologies are suitable for reproducing porous samples designed for sound absorption. The work is an inter-laboratory test, in which the production of samples and their acoustic measurements are carried out independently by different laboratories, sharing only the same geometry codes describing agreed periodic cellular designs. Different additive manufacturing technologies and equipment are used to make samples. Although most of the results obtained from measurements performed on samples with the same cellular design are very close, it is shown that some discrepancies are due to shape and surface imperfections, or microporosity, induced by the manufacturing process. The proposed periodic cellular designs can be easily reproduced and are suitable for further benchmarking of additive manufacturing techniques for rapid prototyping of acoustic materials and metamaterials.
Journal article
(2020)
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Huiqing Wang, Jieun Yang, Maarten Hornikx
Accurate modeling of boundary conditions is of critical importance for acoustic simulations. Recently, the time-domain nodal discontinuous Galerkin (TD-DG) method has emerged as a potential wave-based method for acoustic modeling. Although the acoustic reflection behavior of various time-domain impedance boundaries has been studied extensively, the modeling of the sound transmission across a locally-reacting layer of impedance discontinuity is far less developed. This paper presents a formulation of broadband time-domain transmission boundary conditions for locally-reacting surfaces in the framework of the TD-DG method. The formulation simulates the acoustic wave behavior at each of the boundary nodes using the plane-wave theory. Through the multi-pole model representation of the transmission coefficient, various types of transmission layers can be simulated. One-dimensional numerical examples demonstrate the capability of the proposed formulation to accurately simulate the reflection and transmission characteristics of the limp wall and the porous layer, where quantitative error behavior against analytical results is presented. Furthermore, to demonstrate the applicability, two scenarios of two-dimensional acoustic environment are considered. One is the sound transmission between two rooms partitioned by a limp panel and the other is the sound propagation through a transmissive noise barrier. Comparison of the predicted results from the proposed method against the results from the frequency-domain finite element simulations further verifies the formulation.
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Accurate modeling of boundary conditions is of critical importance for acoustic simulations. Recently, the time-domain nodal discontinuous Galerkin (TD-DG) method has emerged as a potential wave-based method for acoustic modeling. Although the acoustic reflection behavior of various time-domain impedance boundaries has been studied extensively, the modeling of the sound transmission across a locally-reacting layer of impedance discontinuity is far less developed. This paper presents a formulation of broadband time-domain transmission boundary conditions for locally-reacting surfaces in the framework of the TD-DG method. The formulation simulates the acoustic wave behavior at each of the boundary nodes using the plane-wave theory. Through the multi-pole model representation of the transmission coefficient, various types of transmission layers can be simulated. One-dimensional numerical examples demonstrate the capability of the proposed formulation to accurately simulate the reflection and transmission characteristics of the limp wall and the porous layer, where quantitative error behavior against analytical results is presented. Furthermore, to demonstrate the applicability, two scenarios of two-dimensional acoustic environment are considered. One is the sound transmission between two rooms partitioned by a limp panel and the other is the sound propagation through a transmissive noise barrier. Comparison of the predicted results from the proposed method against the results from the frequency-domain finite element simulations further verifies the formulation.
Conference paper
(2020)
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Baltazar Briere de La Hosseraye, Maarten Hornikx, Jieun Yang
Journal article
(2018)
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Jieun Yang, Joong Seok Lee, Hyeong Rae Lee, Yeong June Kang, Yoon Young Kim
Sound transmission reduction is typically governed by the mass law, requiring thicker panels to handle lower frequencies. When open holes must be inserted in panels for heat transfer, ventilation, or other purposes, the efficient reduction of sound transmission through holey panels becomes difficult, especially in the low-frequency ranges. Here, we propose slow-wave metamaterial open panels that can dramatically lower the working frequencies of sound transmission loss. Global resonances originating from slow waves realized by multiply inserted, elaborately designed subwavelength rigid partitions between two thin holey plates contribute to sound transmission reductions at lower frequencies. Owing to the dispersive characteristics of the present metamaterial panels, local resonances that trap sound in the partitions also occur at higher frequencies, exhibiting negative effective bulk moduli and zero effective velocities. As a result, low-frequency broadened sound transmission reduction is realized efficiently in the present metamaterial panels. The theoretical model of the proposed metamaterial open panels is derived using an effective medium approach and verified by numerical and experimental investigations.
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Sound transmission reduction is typically governed by the mass law, requiring thicker panels to handle lower frequencies. When open holes must be inserted in panels for heat transfer, ventilation, or other purposes, the efficient reduction of sound transmission through holey panels becomes difficult, especially in the low-frequency ranges. Here, we propose slow-wave metamaterial open panels that can dramatically lower the working frequencies of sound transmission loss. Global resonances originating from slow waves realized by multiply inserted, elaborately designed subwavelength rigid partitions between two thin holey plates contribute to sound transmission reductions at lower frequencies. Owing to the dispersive characteristics of the present metamaterial panels, local resonances that trap sound in the partitions also occur at higher frequencies, exhibiting negative effective bulk moduli and zero effective velocities. As a result, low-frequency broadened sound transmission reduction is realized efficiently in the present metamaterial panels. The theoretical model of the proposed metamaterial open panels is derived using an effective medium approach and verified by numerical and experimental investigations.
Journal article
(2017)
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Jieun Yang, Joong Seok Lee, Yoon Young Kim
Sound absorption for a broad frequency range requires sound dissipation. The mechanics of acoustic metamaterials for non-dissipative applications has been extensively studied, but sound absorption using dissipative porous metamaterials has been less explored because of the complexity resulting from the coupling of its dissipative mechanism and metamaterial behavior. We investigated broadband sound absorption by engineering dissipative metaporous layers, which absorb sound by the mechanism of multiple slow waves, and combined local and global resonance phenomena. A set of rigid partitions of varying lengths was elaborately inserted in a hard-backed porous layer of a finite thickness. An effective medium theory was used to explain the physics involved; high performance at a low-frequency range was found to be mainly due to the formation of global resonances caused by multiple slow waves over the thickness of the metaporous layer, while enhancement at a high-frequency range was attributed to the combined effects of the global resonances and the local resonances directly related to the sizes of the inserted partitions.
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Sound absorption for a broad frequency range requires sound dissipation. The mechanics of acoustic metamaterials for non-dissipative applications has been extensively studied, but sound absorption using dissipative porous metamaterials has been less explored because of the complexity resulting from the coupling of its dissipative mechanism and metamaterial behavior. We investigated broadband sound absorption by engineering dissipative metaporous layers, which absorb sound by the mechanism of multiple slow waves, and combined local and global resonance phenomena. A set of rigid partitions of varying lengths was elaborately inserted in a hard-backed porous layer of a finite thickness. An effective medium theory was used to explain the physics involved; high performance at a low-frequency range was found to be mainly due to the formation of global resonances caused by multiple slow waves over the thickness of the metaporous layer, while enhancement at a high-frequency range was attributed to the combined effects of the global resonances and the local resonances directly related to the sizes of the inserted partitions.