The Swiss voice in the world since 1935
Top stories
Stay in touch with Switzerland

Using sound waves to make large objects invisible

Hervé Lissek, head of the acoustics research group at EPFL’s Signal Processing Laboratory
Alain Herzog (EPFL)

A team of researchers has discovered an acoustic technique to make objects invisible using sound waves. Their system of acoustic relays could potentially be used to hide large objects like submarines. 

The scientists from Lausanne’s Federal Institute of Technology (EPFL), in association with the Technical University of Vienna and the University of Crete, devised a system of acoustic relays placed at strategic locations that enabled sound waves to propagate at constant amplitude regardless of what was in their path.

Typically, waves bounce and disperse when they meet any object. This causes the energy waves to scatter and become less intense as they move away from the object. It also makes transmitting data or energy using wave-scattering media almost impossible.

The new system allows sound waves to travel across such media without any 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 PhysicsExternal link.

“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,” Romain Fleury, head of EPFL’s Laboratory of Wave Engineering, said in a statementExternal link.

They tested their system in a 3.5-metre-long air-filled tube and inside placed various obstacles, such as walls, porous materials and chicanes. They then placed their tiny speakers between the obstacles and set up electronic controls to adjust the speakers’ acoustic properties. 

“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,” added EPFL co-author Etienne Rivet.

Their new method uses programmable circuits to control several speakers simultaneously and in real time. It 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.

Popular Stories

Most Discussed

News

Cyberattacks on Swiss companies increase by 9 per cent

More

Cyberattacks on Swiss companies increase by 9%

This content was published on Swiss companies are increasingly being targeted by cyber criminals. In the past quarter, every single company in this country was the target of a cyber attack an average of 1097 times a week.

Read more: Cyberattacks on Swiss companies increase by 9%
21 minutes of power interruption per end customer in 2024

More

Swiss households faced 21 minutes of power outages in 2024

This content was published on End customers experienced an average of 21 minutes of electricity interruption in 2024. This resulted in 0.34 power outages per capita. The duration of electricity interruptions increased by three minutes compared to the previous year.

Read more: Swiss households faced 21 minutes of power outages in 2024
SMEs struggle to find staff, 'employees have more power'

More

Swiss SMEs struggling to find employees

This content was published on Swiss small and medium-sized enterprises (SMEs) are struggling to find staff, a problem made more acute by the increased bargaining power of employees and increased absenteeism.

Read more: Swiss SMEs struggling to find employees
Demonstrators attack Israeli mission in Geneva

More

Activists deface Israel’s UN mission in Geneva

This content was published on Late on Thursday in Geneva, pro-Palestinian demonstrators attacked the Permanent Mission of Israel to the United Nations in the international organisations district. They poured red paint over the entrance to the building.

Read more: Activists deface Israel’s UN mission in Geneva

In compliance with the JTI standards

More: SWI swissinfo.ch certified by the Journalism Trust Initiative

You can find an overview of ongoing debates with our journalists here . Please join us!

If you want to start a conversation about a topic raised in this article or want to report factual errors, email us at english@swissinfo.ch.

SWI swissinfo.ch - a branch of Swiss Broadcasting Corporation SRG SSR

SWI swissinfo.ch - a branch of Swiss Broadcasting Corporation SRG SSR