Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New metamaterial manipulates sound to improve acoustic imaging

17.12.2015

Researchers from North Carolina State University and Duke University have developed a metamaterial made of paper and aluminum that can manipulate acoustic waves to more than double the resolution of acoustic imaging, focus acoustic waves, and control the angles at which sound passes through the metamaterial. Acoustic imaging tools are used in both medical diagnostics and in testing the structural integrity of everything from airplanes to bridges.

"This metamaterial is something that we've known is theoretically possible, but no one had actually made it before," says Yun Jing, an assistant professor of mechanical and aerospace engineering at NC State and corresponding author of a paper describing the work.


The metamaterial, shown here, is made of paper and aluminum -- but its structure allows it to manipulate acoustic waves to more than double the resolution of acoustic imaging, focus acoustic waves, and control the angles at which sound passes through the metamaterial. Acoustic imaging tools are used in both medical diagnostics and in testing the structural integrity of everything from airplanes to bridges.

Credit: Chen Shen, North Carolina State University

Metamaterials are simply materials that have been engineered to exhibit properties that are not found in nature. In this case, the structural design of the metamaterial gives it qualities that make it a "hyperbolic" metamaterial. This means that it interacts with acoustic waves in two different ways.

From one direction, the metamaterial exhibits a positive density and interacts with acoustic waves normally - just like air. But from a perpendicular direction, the metamaterial exhibits a negative density in terms of how it interacts with sound. This effectively makes acoustic waves bend at angles that are the exact opposite of what basic physics would tell you to expect.

The practical effect of this is that the metamaterial has some very useful applications.

For one thing, the metamaterial can be used to improve acoustic imaging. Traditionally, acoustic imaging could not achieve image resolution that was smaller than half of a sound's wavelength. For example, an acoustic wave of 100 kilohertz (kHz), traveling through air, has a wavelength of 3.4 millimeters (mm) - so it couldn't achieve image resolution smaller than 1.7 mm.

"But our metamaterial improves on that," says Chen Shen, a Ph.D. student at NC State and lead author of the paper. "By placing the metamaterial between the imaging device and the object being imaged, we were able to more than double the resolution of the acoustic imaging - from one-half the sound's wavelength to greater than one-fifth."

The metamaterial can also focus acoustic waves, which makes it a flexible tool.

"Medical personnel and structural engineers sometimes need to focus sound for imaging or therapeutic purposes," Jing says. "Our metamaterial can do that, or it can be used to improve resolution. There are few tools out there that can do both."

Lastly, the metamaterial gives researchers more control over the angle at which acoustic waves can pass through it.

"For example, the metamaterial could be designed to block sound from most angles, leaving only a small opening for sound to pass through, which might be useful for microphones," Shen says. "Or you could leave it wide open - it's extremely flexible."

Right now, the prototype metamaterial is approximately 30 centimeters square, and is effective for sounds between 1 and 2.5 kHz.

"Our next steps are to make the structure much smaller, and to make it operate at higher frequencies," Jing says.

###

The paper, "Broadband Acoustic Hyperbolic Metamaterial," was published online Dec. 16 in the journal Physical Review Letters. The paper was co-authored by Ni Sui of NC State and Yangbo Xie, Wenqi Wang and Steven Cummer of Duke.

Media Contact

Matt Shipman
matt_shipman@ncsu.edu
919-515-6386

 @NCStateNews

http://www.ncsu.edu 

Matt Shipman | EurekAlert!

More articles from Materials Sciences:

nachricht Strange but true: Turning a material upside down can sometimes make it softer
20.10.2017 | Universitat Autonoma de Barcelona

nachricht Metallic nanoparticles will help to determine the percentage of volatile compounds
20.10.2017 | Lomonosov Moscow State University

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>