Rainbows can be made from sounds – and we’ve created the best ones yet
Two research teams have independently created devices within which sound waves could be separated by frequency, creating the most complete sound rainbows yet
Researchers have successfully captured and imaged full rainbows made of sound for the first time, marking a significant breakthrough in the field. By harnessing techniques similar to those used for sorting light by frequency, scientists have now developed methods to sort sound waves based on their frequency as well. This achievement opens up possibilities for creating new sound-based devices for information processing and energy harvesting.
To create these elastic rainbows, researchers trapped quantum excitations called phonons—vibrations within materials—into groups by frequency. They then manipulated each group to stay in different locations within a device. The teams drew inspiration from how the motion of electrons in thin materials can be constrained by electromagnetic fields, and engineered their devices with microscopic patterns, such as tiny triangular pillars.
When phonons moved through these patterns, their speed and direction of motion changed, effectively steering the vibrations.
The researchers observed that once the phonons formed a rainbow in this manner, it could be used to route incoming elastic waves, much like guiding light through a rainbow of colors. One team imaged their rainbow by illuminating it with a laser and recording the subsequent vibrations using ultrasonic sound beyond human hearing.
These experiments demonstrate that elastic rainbows can be practically made and manipulated, offering convincing proof of their potential applications. The connection to electron physics may even enable exploration of quantum effects and phenomena from Albert Einstein's special relativity in new materials settings. Potential applications include the creation of vibration filters, ultrasonic routers, sensitive mechanical sensors, and devices that harvest energy from elastic waves.
However, the existing devices would need to be made smaller and the amount of vibrational energy trapped within the rainbow would need to be increased for these applications to become more practical. Researchers are already working on these improvements, with promising results in sight.
Written by urgent.news from New Scientist's reporting — not their text. Machine-written — it may contain errors, so check the original before relying on it.
