Acoustic black holes (ABHs) are known as efficient structural dampers. Periodic lattices are identified as an efficient way to forbidden wave propagation in targeted frequency bandgaps (BGs). The paper demonstrates the possibility to merge the ABH effect with Bragg BGs. The geometrical layout leading to this double effect consists of a plate of periodically modulated thickness by a combination of cosine functions of the spatial coordinates constituting an ABH-like cell, coated with a thin damping layer. The resulting metamaterial allows the realization of solid, stiff, and nonresonant panels over a wide frequency range, including low frequencies, without increasing the mass. First, the band structure is analyzed in the conservative case (without damping layer) using a plane wave expansion model following Kirchhoff's assumptions. The results show the existence of low-frequency BGs that can be controlled by only three geometric parameters, which are defined on the type of lattice chosen (square or hexagonal). Next, a finite size panel is designed for the hexagonal lattice. Experimental characterization of the demonstrator with and without viscoelastic coating shows very attractive broadband vibration mitigation performances due to the fact that the dissipation produced by the ABH effect does not deter filtering effects produced in the BG.
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http://dx.doi.org/10.1121/10.0025926 | DOI Listing |
Sensors (Basel)
November 2024
Hubei Key Laboratory of Optical Information and Pattern Recognition, Wuhan Institute of Technology, Wuhan 430205, China.
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November 2024
Department of Chemistry, Technical University of Denmark, Kemitorvet 206, 2800 Kongens Lyngby, Denmark.
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School of Electronic Science and Engineering, Southeast University, Nanjing 210096, China.
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View Article and Find Full Text PDFPLoS One
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Xilinhot Earthquake Monitoring Center Station, Xilinhot, Inner Mongolia Autonomous Region, China.
Analysis of the continuous ambient noise data collected by a dense network of broadband seismic stations reveals the characteristics of ambient noise in densely populated urban areas. A study conducted in central Inner Mongolia utilized ten broadband stations to investigate two distinct repetitive and intense noise signals with predominant frequencies ranging from 1-20 Hz and 0.01-1 Hz.
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