Researchers transfer the concept of an optical invisibility cloak to sound waves

Dec 20, 2011

Progress of metamaterials in nanotechnologies has made the invisibility cloak, a subject of mythology and science fiction, become reality: Light waves can be guided around an object to be hidden, in such a way that this object appears to be non-existent.

This concept applied to electromagnetic may also be transferred to other types of waves, such as . Researchers from Karlsruhe Institute of Technology (KIT) have now succeeded in demonstrating for the first time an invisibility cloak for elastic waves. Such waves also occur in strings of a guitar or drum membranes.

It is as if Harry Potter had a cloak that also makes him unhearable. "Maybe a place of peace and quiet in the Christmas season," say the KIT researchers, who succeeded in transferring the concepts underlying the optical to in a plate.

"The key to controlling waves is to specifically influence their local speed as a function of the 'running direction' of the wave," says Dr. Nicolas Stenger from the Institute of Applied Physics (AP). In his experiment, he used a smartly microstructured material composed of two polymers: A soft and a hard plastic in a thin plate. The vibrations of this plate are in the range of acoustic frequencies, that is some 100 Hz, and can be observed directly from above. The scientists found that the sound waves are guided around a circular area in the millimeter-thin plate in such a way that vibrations can neither enter nor leave this area. "Contrary to other known noise protection measures, the sound waves are neither absorbed nor reflected," says Professor Martin Wegener from the Institute of Applied Physics and coordinator of the DFG Center for Functional Nanostructures (CFN) at KIT. "It is as if nothing was there." Both physicists and Professor Martin Wilhelm from the KIT Institute for Chemical Technology and Polymer Chemistry have now published their results in the journal Physical Review Letters.

The scientists explain their idea by the following story: A city, in the shape of a circle, suffers from noisy car traffic through its center. Finally, the mayor has the idea to introduce a speed limit for cars that drive directly towards the city: The closer the cars come to the city area, the slower they have to drive. At the same time, the mayor orders to build circular roads around the city, on which the cars are allowed to drive at higher speeds. The cars can approach the city, drive around it, and leave it in the same direction in the end. The time required corresponds to the time needed without the city. From outside, it appears as if the city was not there.

Explore further: Finding faster-than-light particles by weighing them

add to favorites email to friend print save as pdf

Related Stories

Karlsruhe invisibility cloak: Disappearing visibly

May 18, 2011

"Seeing something invisible with your own eyes is an exciting experience," say Joachim Fischer and Tolga Ergin. For about one year, both physicists and members of the team of Professor Martin Wegener at KIT's ...

Acoustic cloaking device echoes advances in optical cloaking

Aug 15, 2011

Optical cloaking devices that enable light to gracefully slip around a solid object were once strictly in the realm of science fiction. Today they have emerged as an exciting area of study, at least on microscopic scales. ...

New invisibility cloak hides objects from human view

Jul 27, 2011

For the first time, scientists have devised an invisibility cloak material that hides objects from detection using light that is visible to humans. The new device is a leap forward in cloaking materials, according to a report ...

Tsunami Invisibility Cloak

Sep 26, 2008

Rather than building stronger ocean-based structures to withstand tsunamis, it might be easier to simply make the structures disappear.

Recommended for you

Finding faster-than-light particles by weighing them

Dec 26, 2014

In a new paper accepted by the journal Astroparticle Physics, Robert Ehrlich, a recently retired physicist from George Mason University, claims that the neutrino is very likely a tachyon or faster-than-light par ...

Controlling core switching in Pac-man disks

Dec 24, 2014

Magnetic vortices in thin films can encode information in the perpendicular magnetization pointing up or down relative to the vortex core. These binary states could be useful for non-volatile data storage ...

Atoms queue up for quantum computer networks

Dec 24, 2014

In order to develop future quantum computer networks, it is necessary to hold a known number of atoms and read them without them disappearing. To do this, researchers from the Niels Bohr Institute have developed ...

New video supports radiation dosimetry audits

Dec 23, 2014

The National Physical Laboratory (NPL), working with the National Radiotherapy Trials Quality Assurance Group, has produced a video guideĀ to support physicists participating in radiation dosimetry audits.

Acoustic tweezers manipulate cell-to-cell contact

Dec 22, 2014

Sound waves can precisely position groups of cells for study without the danger of changing or damaging the cells, according to a team of Penn State researchers who are using surface acoustic waves to manipulate ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

Dichotomy
1.3 / 5 (3) Dec 20, 2011
incidentally, anyone inside this cloaked area is unable to see (or hear as the case may be) what is going on outside the cloaked area since our senses are passive receptors of these very signals/wavelengths.

I can only imagine how things went when the Klingons (aka secret government agencies you can't get rid of) turned on their cloaking device for the first time and wondered where everything around them went!

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.