scholarly journals The required acoustic parameters simplification of invisibility cloaks and concentrators using the impedance-tunable coordinate transformation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jun Cao ◽  
Fenghua Qi ◽  
Senlin Yan
Keyword(s):  
Coordinate Transformation ◽  
Two Dimensional ◽  
Acoustic Metamaterials ◽  
Acoustic Parameters ◽  
Acoustic Design ◽  
Impedance Distribution ◽  
Invisibility Cloaks ◽  
Impedance Functions ◽  
Transformation Acoustics ◽  
Tunable Impedance

AbstractTransformation acoustics, as an unconventional theory, provides a powerful tool to design various kinds of acoustic devices with excellent functionalities. However, the required ideal parameters, which are prescribed by the method, are both complex and hard to implement-even using acoustic metamaterials. Furthermore, simplified parameter materials are generally favored in transformation-acoustic design due to its easier realization with artificial structures. In this letter, we propose a coordinate transformation methodology for achieving simplified parameters by tuning the impedance distribution in the geometric limit, where the transformation media parameters can be derived by setting tunable impedance functions in the original space and a combination of suitable linear or nonlinear coordinate transformation. Based on this approach, both two-dimensional acoustic cloak and concentrators are designed with different sets of simplified parameters. Numerical simulations indicate good performance of these devices with minimized scattering at higher frequencies. The proposed method provides more opportunities to realize the designed acoustic devices experimentally, and can also be used for other transformation-acoustic designs including 3D cases.

Acoustic Metamaterial Design Method Based on Green Coordinate Transformation

2020 ◽  
Vol 976 ◽  
pp. 15-24
Author(s):  
Xin Xie ◽  
Xiao Ming Wang ◽  
Yu Lin Mei
Keyword(s):  
Coordinate Transformation ◽  
Design Method ◽  
Three Dimensional ◽  
Transformation Method ◽  
Propagation Path ◽  
Acoustic Metamaterials ◽  
Acoustic Wave Propagation ◽  
Acoustic Metamaterial ◽  
Coordinate Transformation Method ◽  
Transformation Acoustics

Acoustic metamaterials have great application prospects in eliminating vibration and noise, but they are difficult to manufacture due to their anisotropy. This paper utilizes the Green coordinate transformation method to design acoustic metamaterials by combining with the transformation acoustics theory. Because the Green coordinate transformation is the pseudo-conformal mapping in three-dimensional coordinates, the anisotropy of designed metamaterials can be weakened. And also, the genetic algorithm is employed to optimize the anisotropy of metamaterials and reduce the designed metamaterial parameter difference further. Finally, the membrane-imbedded-type metamaterial is applied to realize the design and to illustrate the effectiveness of the proposed method by manipulating the acoustic wave propagation path.

Quasi-two-dimensional acoustic metamaterials

2014 ◽  
Author(s):  
D. Torrent ◽  
R. Graciá-Salgado ◽  
V. M. García-Chocano ◽  
F. Cervera ◽  
J. Sánchez-Dehesa
Keyword(s):  
Two Dimensional ◽  
Acoustic Metamaterials

Sound-transparent anisotropic media for backscattering-immune wave manipulation

2022 ◽  
Author(s):  
Wei-Wei Kan ◽  
Qiu-Yu Li ◽  
Lei Pan
Keyword(s):  
Acoustic Signal ◽  
Acoustic Signals ◽  
Acoustic Medium ◽  
Subwavelength Structures ◽  
Beam Splitting ◽  
Acoustic Parameters ◽  
Straight Path ◽  
Specific Order ◽  
Anisotropic Layers ◽  
Transformation Acoustics

Abstract The scattering behavior of the anisotropic acoustic medium is analyzed to reveal the possibility of routing acoustic signals through the anisotropic layers with no backscattering loss. The sound-transparent effect of such medium is achieved by independently modulating the anisotropic effective acoustic parameters in a specific order, and experimentally observed in a bending waveguide by arranging the subwavelength structures in the bending part according to transformation acoustics. With the properly designed filling structures, the original distorted acoustic field in the bending waveguide is restored as if the wave travels along a straight path. The transmitted acoustic signal is maintained nearly the same as the incident modulated Gaussian pulse. The proposed schemes and the supporting results could be instructive for further acoustic manipulations such as wave steering, cloaking and beam splitting.

scholarly journals Effect of Stage Volume Ratio on Audience Acoustics in Concert Halls

2020 ◽  
Vol 12 (4) ◽  
pp. 1370 ◽  
Author(s):  
Jin Yong Jeon ◽  
Rosa Seo ◽  
Hyun In Jo
Keyword(s):  
Computer Simulation ◽  
Simple Model ◽  
Volume Ratio ◽  
Acoustic Parameter ◽  
Acoustic Parameters ◽  
Design Factor ◽  
Acoustic Design ◽  
Critical Design ◽  
Study Results ◽  
Concert Halls

This report proposes the stage volume ratio (Vo/V) as an acoustic design factor for concert halls and presents an investigation of the dependence of the acoustic parameters of an auditorium on the stage volume through computer simulation. Firstly, the ratio of the stage volume to the total volume of a concert hall was defined as Vo/V through case studies of existing concert halls. It was verified using a simple model that the stage acoustic parameter STEarly and audience acoustic parameters G and C80 decreased, whereas, the reverberation time and early decay time increased with increasing Vo/V. Secondly, a computer simulation was performed for nine existing concert halls, while changing Vo/V from −20% to 30%. The room acoustic parameters exhibited the same patterns as suggested by the simple model. Vo/V significantly affected the bass ratio and bass index. A comparison of the effects of Vo/V and the sound absorption coefficient in nine concert halls revealed that Vo/V contributed approximately 15% to the reverberation and affected the bass characteristics more substantially. Thus, Vo/V is a critical design factor when determining the warmth of the audience acoustics. The study results could be used as a basis for acoustic design in the future.

Arbitrary shaped acoustic omnidirectional absorber based on transformation theory

2020 ◽  
Vol 34 (11) ◽  
pp. 2050111
Author(s):  
Weikai Xu ◽  
Yingchun Tang ◽  
Meng Zhang ◽  
Wuchao Qi ◽  
Wei Wang
Keyword(s):  
Numerical Simulations ◽  
Elastic Waves ◽  
Sound Absorption ◽  
Acoustic Absorption ◽  
Two Dimensional ◽  
Acoustic Path ◽  
Transformation Theory ◽  
Material Parameters ◽  
Arbitrary Geometries ◽  
Transformation Acoustics

In this study, an arbitrary shaped acoustic omnidirectional absorber (AOA) is achieved for absorbing incoming acoustic/elastic waves in the ambient environment. Using the transformation acoustics theory, we present a theoretical framework for two-dimensional acoustic path guidance around arbitrary shapes for which the material parameters in the transformed space can be obtained analytically. Results indicate that the transformed space is distorted rather than compressed; numerical simulations confirm that these absorbers exhibit a remarkably large absorption and that the proposed method can control acoustic absorption for arbitrary geometries of interest. This method can potentially be applied to sound absorption and noise control.

Design of an acoustic bending waveguide with acoustic metamaterials via transformation acoustics

2012 ◽  
Vol 109 (3) ◽  
pp. 523-533 ◽  
Author(s):  
Liang-Yu Wu ◽  
Tzeh-Yi Chiang ◽  
Chia-Nien Tsai ◽  
Mei-Ling Wu ◽  
Lien-Wen Chen
Keyword(s):  
Acoustic Metamaterials ◽  
Transformation Acoustics

scholarly journals Two-Dimensional Composite Acoustic Metamaterials of Rectangular Unit Cell from Pentamode to Band Gap

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1457
Author(s):  
Qi Li ◽  
Ke Wu ◽  
Mingquan Zhang
Keyword(s):  
Wave Propagation ◽  
Acoustic Wave ◽  
Band Gap ◽  
Unit Cell ◽  
The Other ◽  
Two Dimensional ◽  
Acoustic Metamaterials ◽  
Acoustic Wave Propagation ◽  
Theoretical Support ◽  
Unit Cells

Pentamode metamaterials have been receiving an increasing amount of interest due to their water-like properties. In this paper, a two-dimensional composite pentamode metamaterial of rectangular unit cell is proposed. The unit cells can be classified into two groups, one with uniform arms and the other with non-uniform arms. Phononic band structures of the unit cells were calculated to derive their properties. The unit cells can be pentamode metamaterials that permit acoustic wave travelling or have a total band gap that impedes acoustic wave propagation by varying the structures. The influences of geometric parameters and materials of the composed elements on the effective velocities and anisotropy were analyzed. The metamaterials can be used for acoustic wave control under water. Simulations of materials with different unit cells were conducted to verify the calculated properties of the unit cells. The research provides theoretical support for applications of the pentamode metamaterials.

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