ETH Zurich researchers have recently achieved a significant breakthrough in the field of sound wave propagation. Traditionally, sound waves have been known to travel in both forward and backward directions, leading to unwanted reflections in technical applications. However, this new method developed by the researchers could potentially revolutionize the way we control the direction of sound waves.
Led by Professor Nicolas Noiray, the team at ETH Zurich collaborated with Romain Fleury at EPFL to develop a method that prevents sound waves from traveling backward without compromising their propagation in the forward direction. This innovative approach is based on the concept of self-oscillations, where a dynamical system repeats its behavior periodically. This method opens up new possibilities for controlling the direction of sound waves in various applications.
The key to this breakthrough lies in the use of a circulator, a device that allows sound waves to pass only in one direction without any losses. The circulator consists of a disk-shaped cavity through which swirling air is blown, creating a whistling sound in the cavity. Unlike traditional whistles, where sound is produced by a standing wave, the new circulator generates sound from a spinning wave. This unique design enables the circulator to synchronize with incoming waves, allowing them to gain energy and propagate in the desired direction.
After years of theoretical modeling and experimentation, the researchers at ETH Zurich successfully demonstrated the effectiveness of their loss-compensation approach. By sending a sound wave with a frequency of around 800 Hertz through the circulator, they were able to show that the wave could only exit in the forward direction, without any backward propagation. In fact, the sound wave emerged from the circulator even stronger than the original input, showcasing the potential of this new technology.
Professor Noiray envisions this breakthrough as a stepping stone towards manipulating waves in various systems. This concept of loss-compensated non-reciprocal wave propagation could have far-reaching implications for other fields, such as electromagnetic waves. By applying this approach to metamaterials, for example, researchers could improve the guidance of microwaves in radar systems and create topological circuits for future communications systems.
The groundbreaking research conducted by the team at ETH Zurich represents a significant advancement in the field of sound wave propagation. By harnessing the power of self-oscillations and circulators, they have paved the way for a new era of wave manipulation and control. This innovative approach not only opens up new possibilities for technical applications but also promises to revolutionize the way we think about wave propagation in general.
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