Making opaque materials totally transparent

This method could eventually be used to make it possible to hide objects like submarines.

© Jamani Caillet / 2018 EPFL
© Jamani Caillet / 2018 EPFL

Most of the organic materials have a cluttered nuclear structure that meddles with the engendering of both sound and electromagnetic waves. At the point when the waves come into contact with these materials, they bob around and disperse – and their energy disseminates as per a profoundly complex obstruction design, reducing in power. That implies it’s practically difficult to transmit information or energy flawless crosswise over wave-dispersing media and completely use the capability of wave innovation.

For a case, you require to look no more distant than your cell phone – the geolocation work works less well inside structures where radiofrequency waves scramble every which way. Other potential applications incorporate biomedical imaging and land reviewing, where it’s critical to have the capacity to send waves crosswise over exceedingly confused media.

From left to right Hervé Lissek, Romain Fleury and Etienne Rivet© Alain Herzog / 2018 EPFL
From left to right Hervé Lissek, Romain Fleury and Etienne Rivet© Alain Herzog / 2018 EPFL

Now, EPFL scientists have developed a system that allows sound waves to travel across such media with no distortion. It utilizes modest speakers as acoustic transfers to balance the wave disseminating and has been effectively tried on a genuine acoustic framework.

The 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.

In the system, the modest speakers can be controlled to increase, lessen or move the period of the sound waves. That gives them a chance to counterbalance the dissemination that outcomes when the waves hit impediments, and in this manner recreate the first solid precisely on the opposite side of the confused medium.

Romain Fleury, head of EPFL’s Laboratory of Wave Engineering (LWE) and a co-author of the study said, “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.”

Researchers tested their system by building a 3,5 meters in length air-filled tube and putting different sorts of obstructions, for example, dividers, permeable materials, and chicanes into it, with a specific end goal to make a profoundly disarranged medium through which no solid waves could pass. They at that point set their modest speakers between the snags and set up electronic controls to change the speakers’ acoustic properties.

Hervé Lissek, head of the acoustics research group at EPFL’s Signal Processing Laboratory 2 (LTS2) and a co-author of the study said, “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. 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.”

According to scientists, the system could be useful in eliminating the waves that bounce off objects like submarines, making them undetectable by sonar.

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