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Wyświetlanie 1-3 z 3
Tytuł:
Influence of Geometric Structure, Convection, and Eddy on Sound Propagation in Acoustic Metamaterials with Turbulent Flow
Autorzy:
Pak, Myong Chol
Kim, Kwang-Il
Pak, Hak Chol
Hong, Kwon Ryong
Powiązania:
https://bibliotekanauki.pl/articles/2141704.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
acoustic metamaterial
turbulent flow
sound transmission loss
eddy
transportation
Opis:
The problem of reducing noise in transportation is an important research field to prevent accidents and to provide a civilised environment for people. A material that has recently attracted attention in research to reduce noise is acoustic metamaterial, and most of the research projects so far have been limited to the case of static media without flow. We have studied the sound transmission properties of the acoustic metamaterials with turbulent flow to develop the acoustic metamaterials that are used in transportation. In this paper, the effects of geometrical structure, convection, and eddy on sound propagation in the acoustic metamaterials with turbulent flow are investigated, and the relationships between them are analysed. The effects of convection and eddy reduce the resonant strength of the sound transmission loss resulting from the unique geometry of the acoustic metamaterials, but move the resonant frequencies to opposite directions. In addition, when the convective effect and the eddy effect of the airflow, as well as the intrinsic interaction effect generated from the unique geometrical structure of the acoustic metamaterials cannot be ignored, they exhibit competition phenomena with each other, resulting in a widening of the resonance peak. As a result, these three effects cause the shift of the resonance frequency of the sound transmission loss and the widening of the resonance peak. The results of this study show that even in the case of turbulent flow, the metamaterials can be used for transportation by properly controlling its geometric size and shape.
Źródło:
Archives of Acoustics; 2021, 46, 4; 637-647
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of a Geometrical-Stiffening Membrane Acoustic Metamaterial with Individually Tunable Multi-Frequencies
Autorzy:
Zhao, Junjuan
Li, Xianhui
Thompson, David
Wang, Yueyue
Wang, Wenjiang
Zhu, Liying
Liu, Yunan
Powiązania:
https://bibliotekanauki.pl/articles/1953515.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
membrane acoustic metamaterial
nonlinear geometric stiffening
low frequency tuning
sound transmission
Opis:
To realize a structure which can be conveniently tuned to multiple and wideband frequency ranges, a geometrical-stiffening membrane acoustic metamaterial (MAM) with individually tunable multiple frequencies is presented. The MAM is realized by a stacked arrangement of two membrane-magnet elements, each of which has a membrane with a small piece of steel attached in the centre. It can be tuned individually by adjusting the position of its compact magnet. The normal incidence sound transmission loss of the MAM is investigated in detail by measurements in an impedance tube. The test sample results demonstrate that this structure can easily achieve a transmission loss with two peaks which can be shifted individually in a wide low-frequency range. A theoretical consideration is analysed, the analysis shows that the magnetic effect related to this distance leads to a nonlinear attractive force and, consequently, nonlinear geometrical stiffening in each membrane-magnet element, which allows the peaks to be shifted. A reasonable design can make the structure have a good application prospect for low-frequency noise insulation where there is a need to adjust the transmission loss according to the spectrum of the noise source.
Źródło:
Archives of Acoustics; 2021, 46, 1; 87-93
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Perfect absorption for modulus-near-zero acoustic metamaterial in air or underwater at low-frequency
Autorzy:
Gaafer, Fatma Nafaa
Powiązania:
https://bibliotekanauki.pl/articles/2141684.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
acoustic metamaterial
perfect absorption
Fabry-Pérot resonances
subwavelength scale
modulus-near-zero
Opis:
We theoretically propose a method to achieve an optimum absorbing material through a modulus-near-zero (MNZ) metamaterial immersed in air or water with a change in slit width part. The destructive interference has paved the way to achieve perfect absorption (PA). Depending upon theoretical analysis, an acoustic metamaterial (AMMs) that supports resonance with a monopole (140 Hz) is developed to construct a low-frequency sound-absorbing technology. The dissipative loss effect can be by attentively controlling onto slit width to achieve perfect absorption. When there are thin slit width and visco-thermal losses in the structure, it is observed that they lead to high absorption. We use finite element simulations via COMSOL Multiphysics software to theoretical measurement in impedance tube and show the influence of structural parameters in both mediums. The results are of extraordinary correspondence at low frequency to achieve optimum perfect absorption (99%). That might support AMMs to actual engineering-related applications in the process of mitigating noise, slow sound trapping, notch filtering, energy conversion, and time reversal technology.
Źródło:
Archives of Acoustics; 2022, 47, 1; 25-31
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-3 z 3

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