Sound typically travels in waves in all directions from its source, but scientists have developed a device that produces sound waves moving in only one direction.

Imagine three people standing in a circle where only one person hears the speaker. Scientists from ETH Zurich and the Federal Institute of Technology in Lausanne (EPFL) have created a device that can transmit sound waves in a single direction. This innovation holds significant potential for advancing future communication technologies.

Sound waves transmitted in one direction

The device consists of a disk-shaped cavity with three equally spaced connection points. Each connection point can send and receive sound waves. However, when the device is inactive, the connection points hear sound waves equally. That is, the sound sent from one point is perceived at the same level at the other two points and reflects back to the source.

When the system is activated, the situation changes. The device, using air rotating at a specific speed and intensity, ensures that sound waves move in only one direction. For instance, sound from the first point is heard only by the second point, while the third point cannot detect it. As a result, the sound waves move exclusively in a specific direction, reaching their target without losing energy.

The key factor behind the device's success is the synchronization of sound waves with vibrations. This synchronization allows the waves to gain strength as they move in the desired direction, without weakening. Scientists describe this effect as a "rotary junction for sound." The airflow in the circular cavity amplifies the energy of the waves, enabling them to reach the target more powerfully.

This discovery may not be limited to sound waves moving in a single direction. Researchers believe the same method could be used to direct other types of waves, such as electromagnetic waves. This could open up new doors for more efficient radar and communication systems.

In some cases, directing sound waves in only one direction may be crucial. For instance, this technology could be highly beneficial in noise cancellation systems, helping to block unwanted sounds. In 2014, researchers from the University of Texas developed a similar device using an air-driven resonance ring. However, in that device, the sound waves weakened as they traveled. The ETH Zurich team has eliminated this energy loss, allowing the waves to both be directed and gain strength.