Physics

Cloaked in Silence

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Science  12 Apr 2013:
Vol. 340, Issue 6129, pp. 121
DOI: 10.1126/science.340.6129.121-b
CREDIT: L. SANCHIS ET AL., PHYSICAL REVIEW LETTERS 110, 124301 (20 MARCH 2013) HTTP://LINK.APS.ORG/DOI/10.1103/PHYSREVLETT.110.124301 © 2013 AMERICAN PHYSICAL SOCIETY

The daily commute can be a trudge. On top of that, you often have to share, involuntarily, in the irritating noise coming out of the headphones of someone intent on going deaf prematurely. Of course, there are also the more serious safety aspects of protection from sudden and loud noise, as well as the peace and quiet provided by good sound insulation. The ideas developed over the past decade in cloaking an object from view using metamaterials and transformational optics can also be carried to other waveforms, including acoustics. Using such ideas, Sanchis et al. have designed and fabricated a three-dimensional (3D) acoustic cloak for airborne sound. Their cloak consists of a series of concentric tori that surround a sphere about 8 cm in diameter. Designed by an optimization algorithm and using a 3D printing method to fabricate the directional cloak, initial characterization shows that they can reduce the scattering cross section of the sphere for sound of 8.55 kHz by some 90%. A design modification should be possible to make the cloak omnidirectional. Perhaps it won't be too long before such a cloak can be incorporated into headphone design to stop sound leaking out.

Phys. Rev. Lett. 110, 124301 (2013).

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