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Manipulating acoustic wavefront by inhomogeneous impedance and steerable extraordinary reflection.

Zhao J, Li B, Chen Z, Qiu CW - Sci Rep (2013)

Bottom Line: We unveil the connection between the acoustic impedance along a flat surface and the reflected acoustic wavefront, in order to empower a wide wariety of novel applications in acoustic community.Our designed flat surface can generate double reflections: the ordinary reflection and the extraordinary one whose wavefront is manipulated by the proposed impedance-governed generalized Snell's law of reflection (IGSL).The realization of the complex discontinuity of the impedance surface has been proposed using Helmholtz resonators.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576, Republic of Singapore [2] Department of Physics and Centre for Computational Science and Engineering, National University of Singapore, Singapore 117546, Republic of Singapore and.

ABSTRACT
We unveil the connection between the acoustic impedance along a flat surface and the reflected acoustic wavefront, in order to empower a wide wariety of novel applications in acoustic community. Our designed flat surface can generate double reflections: the ordinary reflection and the extraordinary one whose wavefront is manipulated by the proposed impedance-governed generalized Snell's law of reflection (IGSL). IGSL is based on Green's function and integral equation, instead of Fermat's principle for optical wavefront manipulation. Remarkably, via the adjustment of the designed specific acoustic impedance, extraordinary reflection can be steered for unprecedented acoustic wavefront while that ordinary reflection can be surprisingly switched on or off. The realization of the complex discontinuity of the impedance surface has been proposed using Helmholtz resonators.

No MeSH data available.


Wavefront metamorphosis via SAI interface, with impedance discontinuity d = 0.1772.A plane acoustic wave of θ = 15 Krad/s is normally incident in water. Only reflected acoustic pressure is plotted. (a) The SAI of Eq.(7) with ψ(y) = 0.7 y2 is set along the flat surface. pre diverges into a curved wavefront. (b) The SAI of Eq.(7) with  is set. pre converges to a focal point in the two-dimensional case.
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f3: Wavefront metamorphosis via SAI interface, with impedance discontinuity d = 0.1772.A plane acoustic wave of θ = 15 Krad/s is normally incident in water. Only reflected acoustic pressure is plotted. (a) The SAI of Eq.(7) with ψ(y) = 0.7 y2 is set along the flat surface. pre diverges into a curved wavefront. (b) The SAI of Eq.(7) with is set. pre converges to a focal point in the two-dimensional case.

Mentions: To demonstrate IGSL's capability of designing novel acoustic devices, we metamorphose acoustic pressure fields everywhere through SAI manipulation as simulated in Fig. 3. This deceptive effect is obtained by manipulating plane wavefronts into wavefronts generated by a virtual reflector or focusing illumination, governed by the control of pre, i.e., IGSL. Under these scenarios, we need to consider nonlinear forms of ψ(y). New phenomena are thus expected when θre becomes spatially varying.


Manipulating acoustic wavefront by inhomogeneous impedance and steerable extraordinary reflection.

Zhao J, Li B, Chen Z, Qiu CW - Sci Rep (2013)

Wavefront metamorphosis via SAI interface, with impedance discontinuity d = 0.1772.A plane acoustic wave of θ = 15 Krad/s is normally incident in water. Only reflected acoustic pressure is plotted. (a) The SAI of Eq.(7) with ψ(y) = 0.7 y2 is set along the flat surface. pre diverges into a curved wavefront. (b) The SAI of Eq.(7) with  is set. pre converges to a focal point in the two-dimensional case.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3756330&req=5

f3: Wavefront metamorphosis via SAI interface, with impedance discontinuity d = 0.1772.A plane acoustic wave of θ = 15 Krad/s is normally incident in water. Only reflected acoustic pressure is plotted. (a) The SAI of Eq.(7) with ψ(y) = 0.7 y2 is set along the flat surface. pre diverges into a curved wavefront. (b) The SAI of Eq.(7) with is set. pre converges to a focal point in the two-dimensional case.
Mentions: To demonstrate IGSL's capability of designing novel acoustic devices, we metamorphose acoustic pressure fields everywhere through SAI manipulation as simulated in Fig. 3. This deceptive effect is obtained by manipulating plane wavefronts into wavefronts generated by a virtual reflector or focusing illumination, governed by the control of pre, i.e., IGSL. Under these scenarios, we need to consider nonlinear forms of ψ(y). New phenomena are thus expected when θre becomes spatially varying.

Bottom Line: We unveil the connection between the acoustic impedance along a flat surface and the reflected acoustic wavefront, in order to empower a wide wariety of novel applications in acoustic community.Our designed flat surface can generate double reflections: the ordinary reflection and the extraordinary one whose wavefront is manipulated by the proposed impedance-governed generalized Snell's law of reflection (IGSL).The realization of the complex discontinuity of the impedance surface has been proposed using Helmholtz resonators.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576, Republic of Singapore [2] Department of Physics and Centre for Computational Science and Engineering, National University of Singapore, Singapore 117546, Republic of Singapore and.

ABSTRACT
We unveil the connection between the acoustic impedance along a flat surface and the reflected acoustic wavefront, in order to empower a wide wariety of novel applications in acoustic community. Our designed flat surface can generate double reflections: the ordinary reflection and the extraordinary one whose wavefront is manipulated by the proposed impedance-governed generalized Snell's law of reflection (IGSL). IGSL is based on Green's function and integral equation, instead of Fermat's principle for optical wavefront manipulation. Remarkably, via the adjustment of the designed specific acoustic impedance, extraordinary reflection can be steered for unprecedented acoustic wavefront while that ordinary reflection can be surprisingly switched on or off. The realization of the complex discontinuity of the impedance surface has been proposed using Helmholtz resonators.

No MeSH data available.