
EPFL researchers have found a way to make materials that are normally opaque to sound waves completely transparent. Their system involves placing acoustic relays at strategic locations so that sound waves can propagate at a constant amplitude – regardless of what may lie in their path. This method could eventually be used to make it possible to hide objects like submarines.
Most naturally occurring materials have a disordered atomic structure that interferes with the propagation of both sound and electromagnetic waves. When the waves come into contact with these materials, they bounce around and disperse – and their energy dissipates according to a highly complex interference pattern, diminishing in intensity. That means it’s virtually impossible to transmit data or energy intact across wave-scattering media and fully leverage the potential of wave technology.
For an example, you need look no further than your smartphone – the geolocation function works less well inside buildings where radiofrequency waves scatter in all directions. Other potential applications include biomedical imaging and geological surveying, where it’s important to be able to send waves across highly disordered media.
A team of researchers from two labs at EPFL’s School of Engineering, working in association with TU Wien and the University of Crete, has developed a system that allows sound waves to travel across such media with no distortion. It uses tiny speakers as acoustic relays to offset the wave scattering, and has been successfully tested on a real acoustic system. Their work has just been published in Nature Physics.
Using speakers to eliminate obstacles
In the researchers’ system, the tiny speakers can be controlled to amplify, attenuate or shift the phase of the sound waves. That lets them offset the diffusion that results when the waves hit obstacles, and thereby reproduce the original sound exactly on the other side of the disordered medium.
How does it work? “We realized that our acoustic relays had to be able to change the waves’ amplitudes and phases at strategic locations, to either magnify or attenuate them,” says Romain Fleury, head of EPFL’s Laboratory of Wave Engineering (LWE) and a co-author of the study.
The researchers tested their system by building a 3,5 meters long air-filled tube and placing various kinds of obstacles such as walls, porous materials and chicanes into it, in order to create a highly disordered medium through which no sound waves could pass. They then placed their tiny speakers between the obstacles and set up electronic controls to adjust the speakers’ acoustic properties. “We’ve been working on using controlled speakers as active sound absorbers for years, so it made sense to use them for this new application too,” says Hervé Lissek, head of the acoustics research group at EPFL’s Signal Processing Laboratory 2 (LTS2) and a co-author of the study. “Until now, we only needed to attenuate sound waves. But here we had to develop a new control mechanism so we could also amplify them, like how we can already amplify optical waves with lasers,” adds Etienne Rivet, another co-author at EPFL who wrote a thesis on the subject. Their new method – the only one of its kind in acoustics – uses programmable circuits to control several speakers simultaneously and in real time.
Making objects invisible
The researchers’ method for active acoustic control is similar to that used in noise cancelling headphones and could potentially be used for sounds containing common ambient frequencies. It could also be used to eliminate the waves that bounce off objects like submarines, making them undetectable by sonar. Moreover, the theory underlying their work is universal and could have parallel applications in optics or radiofrequencies, to make objects invisible or to take images through opaque materials.
The Latest on: Acoustic invisibility cloak
[google_news title=”” keyword=”acoustic invisibility cloak” num_posts=”10″ blurb_length=”0″ show_thumb=”left”]
via Google News
The Latest on: Acoustic invisibility cloak
- Why quolls have spots, and other ways animals use camouflage to surviveon June 23, 2024 at 9:54 am
Specifically, the texture of the wings of the silk moth (Attacus atlas) act like an acoustic invisibility cloak. Unlike other insect wings, which are covered in scales that reflect sound ...
- Scientists have developed a super-thin, skin-like invisibility cloakon December 4, 2022 at 10:39 pm
Step aside, Harry Potter. There's a new invisibility cloak in town, and while it's still far from being practical, it may one day help you evade detection - no magic necessary. That's the news out ...
- How To Make An 'Invisibility Cloak' At Home For Under $100on November 25, 2022 at 3:56 pm
Watch this device, called the Rochester cloak, in action below, "cloaking" the researchers hand: To first understand how to perform your own disappearing act, here's a basic lesson in lenses.
- Could Star Trek's Invisibility Cloak Become a Reality?on September 15, 2021 at 1:07 pm
Could Star Trek's Invisibility Cloak Become a Reality? On Star Trek, the Romulans possess a cloaking device that renders its ship, the Bird-of-Prey, invisible. Now, years later, a group of ...
- Active Camouflage Material Shows Promise At Hiding From Infrared Or Visual Detectionon January 7, 2021 at 3:21 am
An invisibility cloak may seem like science fiction, but despite that, many scientists and engineers have put much time into developing the concept, pushing it closer to reality. A device which ...
- Metamaterials and Metasurfaces: Engineered Structures Revolutionizing Light and Matter Interactionson August 18, 2020 at 1:09 pm
For example, a metamaterial invisibility cloak would bend the paths of light waves around ... "Printable nanocomposite overcomes the manufacturing limitations of metalenses"). Acoustic metamaterials ...
- Can Harry Potter’s invisibility cloak be made in real life? Scientists at UC Berkeley are hopefulon January 6, 2020 at 7:00 am
Scientists might be a step closer to developing that Harry Potter-style invisibility cloak of your dreams. In 2015, researchers at the University of California, Berkeley, in the US, created a thin ...
- Poundland is now selling invisibility cloaks for Halloweenon October 10, 2019 at 8:28 am
From today six Poundland stores will be offering customers a world-first as part of the retailer’s extensive Halloween range – an invisibility cloak. But, if you want one you'll have to ...
- Acoustic invisibility cloaks and pricked-up earson September 15, 2019 at 12:50 am
Our sensory systems are our access to the world. In an evolutionary arms race, bats and insects interact as predator and prey based on exclusively acoustic information. Using microphone systems in the ...
via Bing News