We design an asymmetric transmission system(ATS)with two flat acoustic metasurfaces(AMs)to yield bidirectional asymmetric acoustic focusing(BAAF).The acoustic waves could be focused on both sides of the ATS with diffe...We design an asymmetric transmission system(ATS)with two flat acoustic metasurfaces(AMs)to yield bidirectional asymmetric acoustic focusing(BAAF).The acoustic waves could be focused on both sides of the ATS with different focal lengths and intensities.To achieve high intensity energy concentration,the accelerating acoustic beams are selected to realize the BAAF.The working bandwidth of the BAAF based on our ATS could reach ～0.4 k Hz.It is found that by adjusting the distance between two flat AMs,the focal length and intensity of the bidirectional focusing could easily be modulated.Because the distance between two flat AMs is large enough,the BAAF even could be converted into a unidirectional acoustic focusing.The proposed BAAF may find applications in non-destructive evaluation,biomedical imaging and medical diagnosis.展开更多
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
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11704193,11674175,and 11704192)the "333" Project of Jiangsu Province,China(Grant No.BRA2017451)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant No.KYCX18_1185)
文摘We design an asymmetric transmission system(ATS)with two flat acoustic metasurfaces(AMs)to yield bidirectional asymmetric acoustic focusing(BAAF).The acoustic waves could be focused on both sides of the ATS with different focal lengths and intensities.To achieve high intensity energy concentration,the accelerating acoustic beams are selected to realize the BAAF.The working bandwidth of the BAAF based on our ATS could reach ～0.4 k Hz.It is found that by adjusting the distance between two flat AMs,the focal length and intensity of the bidirectional focusing could easily be modulated.Because the distance between two flat AMs is large enough,the BAAF even could be converted into a unidirectional acoustic focusing.The proposed BAAF may find applications in non-destructive evaluation,biomedical imaging and medical diagnosis.
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.
