Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Not Only Invisible, but Also Inaudible

KIT Researchers Transfer the Concept of an Optical Invisibility Cloak to Sound Waves

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.

“Circling“ around the silent center: Design (top) and intermediate step of production (bottom) of the elastic invisibility cloak. (Graphics: AP, KIT)

This concept applied to electromagnetic light waves may also be transferred to other types of waves, such as sound waves. 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 invisibility cloak to acoustic waves 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.

Karlsruhe Institute of Technology (KIT) is a public corporation according to the legislation of the state of Baden-Württemberg. It fulfills the mission of a university and the mission of a national research center of the Helmholtz Association. KIT focuses on a knowledge triangle that links the tasks of research, teaching, and innovation.

For further information, please contact:
Margarete Lehné
Presse, Kommunikation und Marketing
Phone: +49 721 608-48121
Fax: +49 721 608-45681
margarete lehneUie9∂kit edu

Monika Landgraf | EurekAlert!
Further information:

More articles from Materials Sciences:

nachricht How nanoscience will improve our health and lives in the coming years
27.10.2016 | University of California - Los Angeles

nachricht 3-D-printed structures shrink when heated
26.10.2016 | Massachusetts Institute of Technology

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Novel light sources made of 2D materials

Physicists from the University of Würzburg have designed a light source that emits photon pairs. Two-photon sources are particularly well suited for tap-proof data encryption. The experiment's key ingredients: a semiconductor crystal and some sticky tape.

So-called monolayers are at the heart of the research activities. These "super materials" (as the prestigious science magazine "Nature" puts it) have been...

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Prototype device for measuring graphene-based electromagnetic radiation created

28.10.2016 | Power and Electrical Engineering

Gamma ray camera offers new view on ultra-high energy electrons in plasma

28.10.2016 | Physics and Astronomy

When fat cells change their colour

28.10.2016 | Life Sciences

More VideoLinks >>>