Experimental investigation of underwater locally multi-resonant metamaterials under high hydrostatic pressure for low frequency sound absorption

Gu, Yinghong; Zhong, Haibin; Bao, Bin; Wang, Q.; Wu, Jiu Hui

doi:10.1016/j.apacoust.2020.107605

Cited by 47 publications

(19 citation statements)

References 38 publications

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“…One reason for this state of affairs is the difficulty of experimental measurements, owing to the large wavelength involved and the required large impedance mismatch of the solid material for a water impedance tube (11,12). As a result, considerable studies on underwater absorption are only limited to theoretical analyses and numerical calculations (13)(14)(15)(16)(17)(18)(19)(20)(21)(22), whose idealized assumptions may not hold in practical scenarios, while almost all the existing experimental works (23)(24)(25)(26)(27)(28)(29)(30), measured in the water impedance tube, are based on small samples, which may not reflect the true performance in complex environments (31). There is simply a lack of research works based on large-scale samples, measured in water pools.…”

Section: Introductionmentioning

confidence: 99%

Underwater metamaterial absorber with impedance-matched composite

Gao

Tinel

et al. 2022

Sci. Adv.

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By using a structured tungsten-polyurethane composite that is impedance matched to water while simultaneously having a much slower longitudinal sound speed, we have theoretically designed and experimentally realized an underwater acoustic absorber exhibiting high absorption from 4 to 20 kHz, measured in a 5.6 m by 3.6 m water pool with the time-domain approach. The broadband functionality is achieved by optimally engineering the distribution of the Fabry-Perot resonances, based on an integration scheme, to attain impedance matching over a broad frequency range. The average thickness of the integrated absorber, 8.9 mm, is in the deep subwavelength regime (~λ/42 at 4 kHz) and close to the causal minimum thickness of 8.2 mm that is evaluated from the simulated absorption spectrum. The structured composite represents a new type of acoustic metamaterials that has high acoustic energy density and promises broad underwater applications.

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Section: Introductionmentioning

confidence: 99%

Underwater metamaterial absorber with impedance-matched composite

Gao

Tinel

et al. 2022

Sci. Adv.

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“…[23][24][25][26][27] Additionally, with the development of underwater sonar detection and recognition technology, 28 in consideration of the low-frequency sound absorption characteristics of LRAM, LRAM is increasingly used in the design and research of the anechoic coating for underwater vehicles. [29][30][31][32][33][34] However, the shortage of the sound absorber with the local resonance mechanism is that the absorption effect is only strong in the resonance peak frequency and in narrow range near it, and the sound absorption is weak at the non-resonant peak, especially in high frequency bands. 35,36 To the authors' knowledge, there are few related studies on impedance gradient structures and the locally resonance coupling calculation and their combined effect on acoustic performance of underwater anechoic coatings so far.…”

Section: Introductionmentioning

confidence: 99%

A hybrid acoustic structure for low-frequency and broadband underwater sound absorption

Jia

Jin

Shi

et al. 2022

Journal of Low Frequency Noise, Vibration and Active Control

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The underwater anechoic coating with local resonant units is an effective method to achieve low-frequency sound absorption. However, the structure obtained in this way is not satisfactory in the sound absorption effect of mid-high frequency bands. Capitalizing on the impedance gradient characteristics of functionally graded materials (FGMs) can improve the impedance matching between the structure and the medium, and enhance the dissipation of sound waves inside the structure. Based on these, we propose an underwater acoustic structure, which can improve and obtain low-frequency and broadband sound absorption performance by embedding local resonators into FGMs. To reveal the sound-absorbing mechanism and further optimize the low-frequency absorption performance of the structure, we conduct quantitative analyses on the parameters of FGMs, the materials and forms of resonators. The results indicate that by appropriately adjusting the studied parameters, different low-frequency sound-absorbing peak can be obtained and the absorption effects are also further improved.

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“…For enhanced low-frequency sound absorption, metallic structures with different topologies were introduced into rubber to form spring-mass resonant metamaterials. [35][36][37][38] In addition, quasi-Helmholtz resonance metamaterials constructed by incorporating rubber into the Helmholtz structure were exploited for lowfrequency underwater sound absorption. [39][40][41] Generally speaking, however, the resonant anechoic structures proposed hitherto by existing studies show a narrow frequency bandwidth of sound absorption, thus restricting their practical applications.…”

Section: Introductionmentioning

confidence: 99%

Grating‐like anechoic layer for broadband underwater sound absorption

Duan

et al. 2022

Int Journal of Mech Sys Dyn

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To address the challenging task of effective sound absorption in the low and broad frequency band for underwater structures, we propose a novel grating-like anechoic layer by filling rubber blocks and an air backing layer into metallic grating. The metallic gratings are incorporated into the anechoic layer as a skeleton for enhanced viscoelastic dissipation by promoting shear deformation between rubber and metal plates. The introduction of an air backing layer releases the bottom constraint of the rubber, thus intensifying its deformation under acoustic excitation. Based on the homogenization method and the transfer matrix method, a theoretical model is developed to evaluate the sound absorption performance of the proposed anechoic layer, which is validated against finite element simulation results. It is demonstrated that a sound absorption coefficient of the grating-like anechoic layer of 0.8 can be achieved in the frequency range of 1294-10 000 Hz. Given the importance of sound absorption at varying frequencies, the weighted average method is subsequently used to comprehensively evaluate the performance of the anechoic layer. Then, with structural density taken into consideration, an integrated index is proposed to further evaluate the acoustic properties of the proposed anechoic layer. Finally, the backing conditions and the boundary conditions of finite-size structures are discussed. The results provide helpful theoretical guidance for designing novel acoustic metamaterials with broadband low-frequency underwater sound absorption.

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Experimental investigation of underwater locally multi-resonant metamaterials under high hydrostatic pressure for low frequency sound absorption

Cited by 47 publications

References 38 publications

Underwater metamaterial absorber with impedance-matched composite

Underwater metamaterial absorber with impedance-matched composite

A hybrid acoustic structure for low-frequency and broadband underwater sound absorption

Grating‐like anechoic layer for broadband underwater sound absorption

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