Imagine being able to enjoy music or a podcast without the need for headphones or earbuds while not bothering those around you. Alternatively, consider having a private chat in a public place without others overhearing you.
Our recent research presents a groundbreaking method for creating audible enclaves—localized sound areas that are separated from their environment. In essence, we’ve developed technology that allows sound to be concentrated exactly where it’s needed.
The ability to direct sound to be audible only at specific locations could revolutionize entertainment, communication, and spatial audio experiences.
Understanding Sound
Sound is essentially a vibration that moves through the air in wave form. These waves occur when an object oscillates, compressing and expanding air molecules.
The pitch of these vibrations is determined by their frequency. Lower frequencies produce deeper sounds, such as those from a bass drum, while higher frequencies yield sharper sounds, like a whistle.
Controlling the direction of sound can be challenging due to a phenomenon known as diffraction, where sound waves tend to spread out as they travel. This is particularly pronounced with low-frequency sounds because of their longer wavelengths, making it almost impossible to restrict sound to a particular area.
The Concept of Audible Enclaves
We discovered a new way to direct sound to an individual listener through self-bending ultrasound beams and a method called nonlinear acoustics.
Ultrasound consists of sound waves with frequencies surpassing the human hearing threshold (above 20 kHz). While these waves travel through air like regular sound waves, they are inaudible to humans.
In our research, we utilized ultrasound as a medium for audible sound. This allows sound to travel invisibly through space, becoming audible only where intended. The mechanism involves using two distinct ultrasound beams that are silent on their own. However, when these beams cross paths, nonlinear interactions generate a new audible sound wave that is perceptible solely in that intersection.
Enhancing Sound Control
Creating audio enclaves has numerous potential applications. For instance, they could facilitate personalized audio experiences in public settings, such as providing distinct audio guides in museums without the use of headphones or enabling students in libraries to listen to educational content without disturbing others.
This technology could also allow car passengers to enjoy music while not distracting the driver with navigation instructions. Additionally, workplaces and military environments could implement localized audio zones for private discussions.
Furthermore, audio enclaves could help in canceling out noise in specific areas, producing quiet zones that foster concentration in work environments and mitigate noise pollution in urban areas.
While this technology holds immense promise, there are still challenges to address, such as nonlinear distortion affecting sound quality and power efficiency. Converting ultrasound into audible sound necessitates high-intensity fields that can be energy-demanding to produce.
Despite these challenges, audio enclaves mark a significant progress in sound management. By redefining how sound interacts within spaces, we unveil new opportunities for immersive, personalized, and efficient audio experiences.
Jiaxin Zhong, Postdoctoral Researcher in Acoustics, Penn State and Yun Jing, Professor of Acoustics, Penn State
This article is republished from The Conversation under a Creative Commons license. Read the original article.
