4 min read
0 comments
New technology bends sound and allows only your ears to pick up audio from a crowd. Discover how this system works and its possible applications in everyday life
Imagine listening to a song or podcast in public without needing headphones — and without anyone else hearing you. Or participating in a private conversation in a crowded room without the sound carrying out into the surroundings. A new technology sound, developed by researchers at Penn State University, has just shown that this is possible.
Researchers have developed technology that can create audible enclaves — localized pockets of sound that are isolated from their surroundings. This means that sound becomes audible only at a specific point, without spreading out into space.
With this technique, it is possible to send audio directly to a location or person, without others around hearing it. The discovery could transform how we interact with sound in public and private spaces.
- The James Webb Space Telescope has identified a spiral galaxy similar to the Milky Way
- WhatsApp will stop working on these devices from May 5th
- Scientists have created olo, a never-before-seen blue-green color: understand how lasers stimulated the retina and the controversies surrounding the experiment!
- Sunlight and sugarcane waste drive hydrogen production at four times the commercial standard
How sound behaves
Sound is produced by vibrations that propagate through the air in the form of waves. When an object moves back and forth, it compresses and decompresses air molecules, forming these sound waves.
The frequency of these vibrations determines the pitch of the sound. Low frequencies produce low-pitched sounds, such as a bass drum. High frequencies produce high-pitched sounds, such as a whistle.
Controlling the direction of these sound waves has always been a challenge. This is due to diffraction, a phenomenon that causes waves to spread out as they move. Diffraction is strongest in low-frequency sounds, which makes it even more difficult to confine the sound to a specific area.
Some technologies have been proposed to solve this problem. One example is parametric array loudspeakers, which create targeted beams of sound. However, even these systems still produce sound along the entire path that the beam travels. The sound ends up being heard by people outside the intended target.
The Science Behind Audible Enclaves
The Penn State team took a different approach. They used self-curving ultrasound beams combined with the principle of nonlinear acoustics. Ultrasound consists of waves with frequencies above 20 kHz, which are not audible to humans. These waves are commonly used in medical examinations and industrial applications.
The innovation was to use ultrasound as a carrier for audible sound. This prevented audio from being transported through space silently, making it audible only at the desired point.
The process works like this: normally, sound waves add up in a linear fashion, creating a larger wave. But when these waves are intense or sufficient, they can interact in a non-linear fashion and generate new frequencies.
The team applied two ultrasound beams with different frequencies — which in themselves are silent — but which, when they cross, generate a new audible sound wave exactly at that point of intersection.
Additionally, the researchers developed beams that bend themselves. Using acoustic metasurfaces—materials capable of manipulating the behavior of waves—they can bend the beams to navigate around obstacles and find their way to the exact location they want.
The influence responsible for this is called difference frequency generation. For example, when combining 40 kHz and 39,5 kHz beams, the 0,5 kHz difference generates a new wave that is within the audible range. This sound is only heard where the two beams intersect. At all other points, it remains imperceptible.
Possible Applications
The ability to direct this to a specific point has many applications. In museums, visitors could listen to different audio tracks without using headphones. In libraries, students could listen to lectures without disturbing others. In cars, passengers could listen to music while the driver received directions from the GPS.
Environments such as offices or military sites could also benefit. The technology would allow conversations to take place in localized areas. Another possibility would be to create quiet areas in busy places, keeping noise levels low and improving concentration.
Despite the potential, there are still challenges. Interference caused by the nonlinear interaction of waves can affect sound quality. In addition, the process requires high-intensity ultrasound fields, which require a lot of energy.
Still, the breakthrough represents a major shift in the way sound is controlled. By allowing audio to be precisely shaped in space, the technology offers a new way to create personalized and efficient experiences. The research pushes the boundaries of what is possible in the field of acoustics.
The Penn State team believes that with further development, audible enclaves could be used on a larger scale, redefining how we listen, interact and share in our daily lives.
With information from Singularity Hub.
