A recent breakthrough by researchers at ETH Zurich involves a new way of making it so that sound waves can only travel in one direction. This accomplishment is indicative of broader implications for both acoustic and electromagnetic technologies, especially for communications and radar systems. The team used a circulator; essentially a wheel shaped cavity that directs spinning air, to block sound from flowing backward without reducing forward propulsion. This ‘one way street’ effect for sound waves has previously been difficult because sound waves tend to propagate equally in both directions.
“This concept of loss-compensated non-reciprocal wave propagation is, in our view, an important result that can also be transferred to other systems,”
Noiray explained, highlighting the broader potential applications for electromagnetic waves, such as improving microwave transmission for radar systems.
Working with key collaborators including Romain Fleury, then from EPFL, the research team designed a circulator that utilises self-sustaining aero-acoustic oscillations. Reducing backward propagation while maintaining forward wave strength through these oscillations, which are usually thought of as a problem in acoustic systems such as aircraft engines, were harnessed.
“In contrast to ordinary whistles, in which sound is created by a standing wave in the cavity, in this new whistle it results from a spinning wave,”
explained Tiemo Pedergnana, a former doctoral student in Noiray’s group.
This has caught the interest of industries that heavily rely on sound and electromagnetic wave control. This discovery enhances the efficiency of wave manipulation to enable improvements in radar technology, microwave systems, and possibly future topological circuits for more sophisticated communication networks. The one way sound wave propagation method could become a fundamental tool applicable to many technology sectors with these potential applications.
The research was published in Nature Communications, showcasing the experimental success of this new method. With continued development, this breakthrough could lead to significant advances in both the acoustic and electromagnetic fields, offering a future where communication technologies are faster, more reliable, and energy-efficient.
