Broadband absorption of low-frequency sound waves via a deep subwavelength structure is of great and ongoing interest in research and engineering.Here,we numerically and experimentally present a design of a broadband ...Broadband absorption of low-frequency sound waves via a deep subwavelength structure is of great and ongoing interest in research and engineering.Here,we numerically and experimentally present a design of a broadband lowfrequency absorber based on an acoustic metaporous composite(AMC).The AMC absorber is constructed by embedding a single metamaterial resonator into a porous layer.The finite element simulations show that a high absorption(absorptance A>0.8)can be achieved within a broad frequency range(from 290 Hz to 1074 Hz),while the thickness of AMC is 1/13of the corresponding wavelength at 290 Hz.The broadband and high-efficiency performances of the absorber are attributed to the coupling between the two resonant absorptions and the trapped mode.The numerical simulations and experimental results are obtained to be in good agreement with each other.Moreover,the high broadband absorption can be maintained under random incident acoustic waves.The proposed absorber provides potential applications in low-frequency noise reduction especially when limited space is demanded.展开更多
Transformation acoustics(TA)has emerged as a powerful tool for designing several intriguing conceptual devices,which can manipulate acoustic waves in a flexible manner,yet their applications are limited in Hermitian m...Transformation acoustics(TA)has emerged as a powerful tool for designing several intriguing conceptual devices,which can manipulate acoustic waves in a flexible manner,yet their applications are limited in Hermitian materials.In this work,we propose the theory of complex-coordinate transformation acoustics(CCTA)and verify the effectiveness in realizing acoustic non-Hermitian metamaterials.Especially,we apply this theory for the first time to the design of acoustic parity-time(PT)and antisymmetric parity-time(APT)metamaterials and demonstrate two distinctive examples.First,we use this method to obtain the exceptional points(EPs)of the PT/APT system and observe the spontaneous phase transition of the scattering matrix in the transformation parameter space.Second,by selecting the Jacobian matrix's constitutive parameters,the PT/APT-symmetric system can also be configured to approach the zero and pole of the scattering matrix,behaving as an acoustic coherent perfect absorber and equivalent laser.We envision our proposed CCTAbased paradigm to open the way for exploring the non-Hermitian physics and finding application in the design of acoustic functional devices such as absorbers and amplifiers whose material parameters are hard to realize by using the conventional transformation method.展开更多
A highly efficient absorbing boundary condition suitable for use in the finitedtherence time-domain (FDTD) modelling of acoustic fields is presented in this paper. The new method seeks a least square esthoate of a tra...A highly efficient absorbing boundary condition suitable for use in the finitedtherence time-domain (FDTD) modelling of acoustic fields is presented in this paper. The new method seeks a least square esthoate of a transfer matrix for field components near truncating boundaries by matrir pseud-inversion. The proposed absorbing boundary is considerably more effective than most ekisting ones. The method is also computationally econondcal and robust.The performance of the new method is shown by numerical experiments on a point-source radiation problem, a wedge dimaction problem, and a scattering problem in which a plane wave is scattered by a circular cylinder.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.12174197,11874222,and 12027808)。
文摘Broadband absorption of low-frequency sound waves via a deep subwavelength structure is of great and ongoing interest in research and engineering.Here,we numerically and experimentally present a design of a broadband lowfrequency absorber based on an acoustic metaporous composite(AMC).The AMC absorber is constructed by embedding a single metamaterial resonator into a porous layer.The finite element simulations show that a high absorption(absorptance A>0.8)can be achieved within a broad frequency range(from 290 Hz to 1074 Hz),while the thickness of AMC is 1/13of the corresponding wavelength at 290 Hz.The broadband and high-efficiency performances of the absorber are attributed to the coupling between the two resonant absorptions and the trapped mode.The numerical simulations and experimental results are obtained to be in good agreement with each other.Moreover,the high broadband absorption can be maintained under random incident acoustic waves.The proposed absorber provides potential applications in low-frequency noise reduction especially when limited space is demanded.
基金the National Key Research and Development Program of China(Grant No.2022YFA1404402)the National Natural Science Foundation of China(Grant Nos.12174190,11634006,12074286,and 81127901)+1 种基金the High-Performance Computing Center of Collaborative Innovation Center of Advanced Microstructuresthe the Priority Academic Program Development of Jiangsu Higher Education Institutions。
文摘Transformation acoustics(TA)has emerged as a powerful tool for designing several intriguing conceptual devices,which can manipulate acoustic waves in a flexible manner,yet their applications are limited in Hermitian materials.In this work,we propose the theory of complex-coordinate transformation acoustics(CCTA)and verify the effectiveness in realizing acoustic non-Hermitian metamaterials.Especially,we apply this theory for the first time to the design of acoustic parity-time(PT)and antisymmetric parity-time(APT)metamaterials and demonstrate two distinctive examples.First,we use this method to obtain the exceptional points(EPs)of the PT/APT system and observe the spontaneous phase transition of the scattering matrix in the transformation parameter space.Second,by selecting the Jacobian matrix's constitutive parameters,the PT/APT-symmetric system can also be configured to approach the zero and pole of the scattering matrix,behaving as an acoustic coherent perfect absorber and equivalent laser.We envision our proposed CCTAbased paradigm to open the way for exploring the non-Hermitian physics and finding application in the design of acoustic functional devices such as absorbers and amplifiers whose material parameters are hard to realize by using the conventional transformation method.
文摘A highly efficient absorbing boundary condition suitable for use in the finitedtherence time-domain (FDTD) modelling of acoustic fields is presented in this paper. The new method seeks a least square esthoate of a transfer matrix for field components near truncating boundaries by matrir pseud-inversion. The proposed absorbing boundary is considerably more effective than most ekisting ones. The method is also computationally econondcal and robust.The performance of the new method is shown by numerical experiments on a point-source radiation problem, a wedge dimaction problem, and a scattering problem in which a plane wave is scattered by a circular cylinder.
