Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Thin engineered material perfectly redirects and reflects sound

11.04.2018

Metamaterial device controls transmission and reflection of acoustic waves

Metamaterials researchers at Duke University have demonstrated the design and construction of a thin material that can control the redirection and reflection of sound waves with almost perfect efficiency.


This metamaterial surface has been engineered to perfectly and simultaneously control the transmission and reflection of incoming sound waves.

Credit: Junfei Li


The spacing between the rows and the amount that each individual column is filled in work together to perfectly control the transmission and reflection of a specific frequency of sound as it passes through.

Credit: Junfei Li

While many theoretical approaches to engineer such a device have been proposed, they have struggled to simultaneously control both the transmission and reflection of sound in exactly the desired manner, and none have been experimentally demonstrated.

The new design is the first to demonstrate complete, near-perfect control of sound waves and is quickly and easily fabricated using 3-D printers. The results appear online April 9 in Nature Communications.

"Controlling the transmission and reflection of sound waves this way was a theoretical concept that did not have a path to implementation -- nobody knew how to design a practical structure using these ideas," said Steve Cummer, professor of electrical and computer engineering at Duke. "We solved both of those problems. Not only did we figure out a way to design such a device, we could also make one and test it. And lo and behold, it actually works."

The new design uses a class of materials called metamaterials -- artificial materials that manipulate waves like light and sound through their structure rather than their chemistry. For example, while this particular metamaterial is made out of 3-D printed plastic, it's not the properties of the plastic that are important -- it's the shapes of the device's features that allow it to manipulate sound waves.

The metamaterial is made of a series of rows of four hollow columns. Each column is nearly one-half of an inch on a side with a narrow opening cut down the middle of one side, making it look somewhat like the world's deepest Ethernet port. While the device demonstrated in the paper is 1.6 inches tall and nearly 3.5 feet long, its height and width are irrelevant -- it could theoretically stretch on forever in either direction.

The researchers control how the device manipulates sound through the width of the channels between each row of columns and the size of the cavity inside each individual column. Some columns are wide open while others are nearly closed off.

To understand why, think of someone blowing air across the top of a glass bottle -- the pitch the bottle makes depends on the amount of liquid left inside the bottle. Similarly, each column resonates at a different frequency depending on how much of it is filled in with plastic.

As a sound wave travels through the device, each cavity resonates at its prescribed frequency. This vibration not only affects the speed of the sound wave but interacts with its neighboring cavities to tame both transmission and reflection.

"Previous devices could shape and redirect sound waves by changing the speed of different sections of the wave front, but there was always unwanted scattering," said Junfei Li, a doctoral student in Cummer's laboratory and first author of the paper. "You have to control both the phase and amplitude of both the transmission and reflection of the wave to approach perfect efficiencies."

To make matters more complicated, the vibrating columns not only interact with the sound wave, but also with their surrounding columns. Li needed to write an 'evolutionary computer optimization program,' to work through all the design permutations.

The researchers feed the program the boundary conditions needed on each side of the material to dictate how they want the outgoing and reflected waves to behave. After trying a random set of design solutions, the program mixes various combinations of the best solutions, introduces random "mutations," and then runs the numbers again. After many iterations, the program eventually "evolves" a set of design parameters that provide the desired result.

In the paper, Cummer, Li and colleagues demonstrate that one such set of solutions can redirect a sound wave coming straight at the metamaterial to a sharp 60-degree outgoing angle with an efficiency of 96 percent. Previous devices would have been lucky to achieve 60 percent efficiencies under such conditions. While this particular setup was designed to control a sound wave at 3,000 Hertz -- a very high pitch not dissimilar to getting a "ringing in your ears" -- the metamaterials could be scaled to affect almost any wavelength of sound.

The researchers and their collaborators are next planning to transfer these ideas to the manipulation of sound waves in water for applications such as sonar, although there aren't any ideas for applications in air. At least not yet.

"When talking about waves, I often fall back on the analogue of an optical lens," said Cummer. "If you tried to make really thin eyeglasses using the same approaches that these sorts of devices have been using for sound, they would stink. This demonstration now allows us to manipulate sound waves extremely accurately, like a lens for sound that would be way better than previously possible."

###

This work was supported by the Office of Naval Research (N00014-13-1-0631) and the National Science Foundation (1641084).

Learn More about Metamaterials at Duke.

CITATION: "Systematic design and experimental demonstration of bianisotropic metasurfaces for scattering-free manipulation of acoustic wavefronts." Junfei Li, Chen Shen, Ana Diaz-Rubio, Sergei A. Tretyakov and Steven A. Cummer. Nature Communications, 2018. DOI: 10.1038/s41467-018-03778-9

Media Contact

Ken Kingery
ken.kingery@duke.edu
919-660-8414

 @DukeU

http://www.duke.edu 

Ken Kingery | EurekAlert!
Further information:
http://pratt.duke.edu/about/news/sound-control
http://dx.doi.org/10.1038/s41467-018-03778-9

More articles from Power and Electrical Engineering:

nachricht Silicon as a new storage material for the batteries of the future
24.04.2018 | Christian-Albrechts-Universität zu Kiel

nachricht Improved stability of plastic light-emitting diodes
19.04.2018 | Max-Planck-Institut für Polymerforschung

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: BAM@Hannover Messe: innovative 3D printing method for space flight

At the Hannover Messe 2018, the Bundesanstalt für Materialforschung und-prüfung (BAM) will show how, in the future, astronauts could produce their own tools or spare parts in zero gravity using 3D printing. This will reduce, weight and transport costs for space missions. Visitors can experience the innovative additive manufacturing process live at the fair.

Powder-based additive manufacturing in zero gravity is the name of the project in which a component is produced by applying metallic powder layers and then...

Im Focus: Molecules Brilliantly Illuminated

Physicists at the Laboratory for Attosecond Physics, which is jointly run by Ludwig-Maximilians-Universität and the Max Planck Institute of Quantum Optics, have developed a high-power laser system that generates ultrashort pulses of light covering a large share of the mid-infrared spectrum. The researchers envisage a wide range of applications for the technology – in the early diagnosis of cancer, for instance.

Molecules are the building blocks of life. Like all other organisms, we are made of them. They control our biorhythm, and they can also reflect our state of...

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Quantum Technology for Advanced Imaging – QUILT

24.04.2018 | Information Technology

AWI researchers measure a record concentration of microplastic in arctic sea ice

24.04.2018 | Earth Sciences

Complete skin regeneration system of fish unraveled

24.04.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>