Harry Potter has completed many a dangerous task using an invisibility cloak. For fans of Harry Potter and those desiring to remain invisible when doing anything their heart desires, would no doubt welcome the idea of purchasing their own invisibility cloak. While an item that renders the human form invisible is currently unavailable, scientists are inching closer to such an item, beginning with a cloaking device that masks sound waves.
First theoretically proposed in 2008, the idea has now become a reality. The item, described in Physical Review Letters, uses much of its technology from similar developments attempting to cloak light.
Using basic plastic sheets featuring a variety of holes, the cloaking device could be used to make ships impervious to sonar, concert halls more acoustically sound (pun intended) and in a variety of other sound-related situations.
Steven Cummer of Duke University,
“Fundamentally, in terms of hiding objects, it’s the same – how anything is sensed is with some kind of wave and you either hear or see the effect of it. But when it comes to building the materials, things are very different between acoustics and electromagnetics. The thing you need to engineer into the materials is very different behaviour in different directions that the wave travels through it.”
Dr. Cummer and his colleagues, through repeated tests, now are displaying an acoustic cloaking technique that works in air, for audible frequencies between one and four kilohertz.
The cloaking shell is made of sheets of plastic featuring holes throughout the sheet. The device works by using stacked sheets of plastic with regular arrays of holes through them. The exact size and placement of the holes on each sheet, and the spacing between the sheets, has a predictable effect on incoming sound waves.
With applicability for shipping, military, home comfort, the music industry and more, the cloaking device is a true marvel.
Should the sound cloaking device be made commercially available, would you consider purchasing it for instillation for your chosen use? What would you use it for?