Metamaterials for transformation acoustics applications

2012 ◽  
Vol 131 (4) ◽  
pp. 3325-3325
Author(s):  
Steven Cummer ◽  
Bogdan Popa
Keyword(s):  
Transformation Acoustics

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.

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.

scholarly journals On the Use of the Analogue Transformation Acoustics in Aeroacoustics

2017 ◽  
Vol 2017 ◽  
pp. 1-16 ◽  
Author(s):  
Umberto Iemma ◽  
Giorgio Palma
Keyword(s):  
Velocity Field ◽  
Fluid Dynamic ◽  
Conformal Mappings ◽  
Governing Equations ◽  
Realistic Potential ◽  
Moving Media ◽  
Analytical Tools ◽  
The Relationship ◽  
Dynamic Conservation ◽  
Transformation Acoustics

The objective of the paper is the assessment of the Analogue Transformation Acoustics (ATA) in the design of acoustic metamaterial for aeronautical applications. The work focuses on the consistency of the background flow resulting from the application of the ATA with the equations governing the potential aerodynamics. Indeed, in case of acoustic perturbations propagating within moving media, the convective terms in the governing equations are responsible for the failure of formal invariance under the action of conformal mappings. The ATA approach overcomes this limitation, introducing the possibility of handling the convective form of the wave equation in a straightforward and elegant way. It is based on the concept of analogue space-time and fully relies on the analytical tools of Lorentzian differential geometry. The present paper analyses the relationship between the analogue velocity field with a realistic potential flow. The method is validated through numerical simulations using two widely assessed acoustic cloaking problems. The preliminary results obtained show that the use of numerical, quasi-conformal mappings can lead to transformed streamlines negligibly deviating from those of the potential velocity field satisfying the fluid-dynamic conservation laws, but with incompatible intensity of the local velocity.

scholarly journals Bending a periodically layered structure for transformation acoustics

2011 ◽  
Vol 98 (24) ◽  
pp. 241914 ◽  
Author(s):  
Zixian Liang ◽  
Jensen Li
Keyword(s):  
Layered Structure ◽  
Transformation Acoustics

scholarly journals Hyperelastic cloaking theory: transformation elasticity with pre-stressed solids

2012 ◽  
Vol 468 (2146) ◽  
pp. 2881-2903 ◽  
Author(s):  
A. N. Norris ◽  
W. J. Parnell
Keyword(s):  
Strain Energy ◽  
Wave Motion ◽  
Deformation Gradient ◽  
Strain Energy Function ◽  
Formal Equivalence ◽  
Isotropic Elasticity ◽  
Symmetry Constraints ◽  
Constitutive Parameters ◽  
Wave Properties ◽  
Transformation Acoustics

Transformation elasticity, by analogy with transformation acoustics and optics, converts material domains without altering wave properties, thereby enabling cloaking and related effects. By noting the similarity between transformation elasticity and the theory of incremental motion superimposed on finite pre-strain, it is shown that the constitutive parameters of transformation elasticity correspond to the density and moduli of small-on-large theory. The formal equivalence indicates that transformation elasticity can be achieved by selecting a particular finite (hyperelastic) strain energy function, which for isotropic elasticity is semilinear strain energy. The associated elastic transformation is restricted by the requirement of statically equilibrated pre-stress. This constraint can be cast as tr F = constant, where F is the deformation gradient, subject to symmetry constraints, and its consequences are explored both analytically and through numerical examples of cloaking of anti-plane and in-plane wave motion.

Research on Layered Design of Ring-Shaped Acoustic Cloaking Using Bimode Metamaterial

2014 ◽  
Vol 687-691 ◽  
pp. 4399-4404
Author(s):  
Qian Jin Xiao ◽  
Lei Wang ◽  
Tao Wu ◽  
Zhi Gao Zhao
Keyword(s):  
Design Method ◽  
Micro Milling ◽  
Physical Parameters ◽  
Microstructure Design ◽  
Research Results ◽  
Processing Capability ◽  
Microstructure Model ◽  
Layered Design ◽  
The Relationship ◽  
Transformation Acoustics

The microstructure design of acoustic cloaking is the key to realizing physical parameters required, and it is also closely correlated with realization of such projects as processing capability. The paper investigates the layered design of ring-shaped acoustic cloaking based on BM. According to the principle of transformation acoustics and the theory of PM cloaking, physical parameters of the acoustic cloaking are offered. Further, the relationship between the parameters of each layer of BM microstructure and the physical parameters of acoustic cloaking made of BM is determined. And the layered design of the acoustic cloaking are discussed. At last, the microstructure model of the acoustic cloaking is designed, and the ultra-precise micro-milling center is adopted for trial produce, to make a sample of the acoustic cloaking. The research results provide a kind of layered design method for ring-shaped acoustic cloaking, and indicat that the acoustic cloaking is realizable in engineering.

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