Engineers from Duke University have created a cloaking device. The cloaking device made is the world’s first three-dimensional acoustic cloak. In other words, the 3D apparatus hides sounds and creates the simulation that the cloaking device and anything underneath it do not actually exist. The sound waves act as is if nothing were there except a flat surface.
The new cloaking device was built out of several perforated sheets of plastic and excessive applications of math. Working in three dimensions, the plastic reroutes the sound waves in such a manner to make it appear not only invisible, but simply not there. Because the device was built for three dimensions, it does not matter from which direction a sound may be coming, or even where the observer is stationed. Regardless of sound direction or observation, the cloak works.
The device was created using a new field of study known as metamaterials. The field of metamaterials is based upon the studies wherein the use of repeating patterns of natural materials can achieve unusual results. To date, only two-dimensional model configurations have achieved the goal of being able to cloak sounds. This new three-dimensional acoustic cloaking apparatus is the world’s first such device.
This new broadband, three-dimensional, and more significantly, omnidirectional, apparatus creates a region of space invisible to sound. The diameter of the space affected is three wavelengths. The device, which looks much like a hole-bedecked pyramid was mainly created from perforated plastic sheets and air. The cloaking device is tasked with the job of altering the sound waves’ trajectories in order to mimic how they would reflect off a flat surface as if the device were not actually there. To that end, the speed of the sound waves needs to be altered. The sound waves are not traveling as far as they would if they were hitting the surface underneath so they are bouncing back faster when they encounter the pyramid. In order to give the impression that the apparatus, and anything underneath it, does not exist, the sound ways must be slowed down.
Invisibility cloaks are not new. In the last few years, several cloaking devices have been created. January 2012 saw researchers at the University of Texas come up with a visual cloaking device. This cloaking device creation was able to cloak objects visually irrespective of the observation point or angle. This three-dimensional plasmonic cloaking device concealed an 18-centimeter cylinder from every direction. However, the experiment only worked with microwaves, not human vision. The researchers believe that with further research and investigations, the device can be made to work in the human visual spectrum as well as with microwaves.
In the meantime, researchers now have the world’s first working model of an acoustic version of a cloaking device which will blind sound three-dimensionally. The applications could be far-reaching. For instance, the technology might have application possibilities in architectural engineering and design. Additionally, sound waves behave in the water the same way as they do in the air, which opens up another field of possible applications. It could be possible for one of the future uses of the acoustic cloaking device to be sonar avoidance.
By Dee Mueller