by What if you could hear music or a podcast without headphones or earphones and without disturbing someone in your area? Or do you have a private conversation in public without hearing other people?
Our newly published research provides a way to create audible enclaves – localized sound bags that are isolated from their surroundings. In other words, we have developed a technology that could create a sound exactly where it has to be.
The ability to send sound that can only be heard at a certain location could change entertainment, communication and spatial audio experiences.
What is sound?
Sound is a vibration that travels through air as a wave. These waves are generated when an object moves back and forth and air molecules compressed and decompressed.
The frequency of these vibrations determines the pitch. Low frequencies correspond to deep sounds like a bass drum; High frequencies correspond to sharp sounds like a pipe.
Control of the sound is difficult because a phenomenon called bend is called the tendency of sound waves to spread during travel. Due to its longer wavelengths, this effect is particularly strong for low -frequency noises, which makes it almost impossible to limit the sound to a certain area.
Certain audio technologies, such as B. parametric array speakers can create focused sound rays that aim in a certain direction. However, these technologies will continue to emit sound that can be audible on its entire path when it flows through the room.
The science of audible enclaves
We found a new way to send a certain listener to a specific listener: through self -bending ultrasound rays and a concept called non -linear acoustics.
Ultrasound refers to sound waves with frequencies above the human hearing area or over 20 kHz. These waves travel through the air like normal sound waves, but are inaudible for humans. Since ultrasound can penetrate through many materials and interact in a unique way with objects, it is often used for medical imaging and many industrial applications.
In our work we used ultrasound as a carrier for audible sound. It can be quietly transported through the room – only audible if it is desired. How did we do that?
Usually sound waves connect linearly, which means that they only add up to a larger wave. However, if sound waves are intense enough, you can interact non -linear and generate new frequencies that were previously not available.
This is the key to our technology: We use two ultrasound rays to different frequencies that are completely quiet in themselves. However, if you cross in space, non -linear effects create a new sound wave with a audible frequency that can only be heard in this special area.
It is crucial that we have designed ultrasound rays that can bend themselves. Usually sound waves travel in straight lines unless they are blocked or reflected on something. By using acoustic metasurfaces – special materials that manipulate sound waves – we can bend ultrasound bars on travel. Similar to an optical lens, slight changes, acoustic metasurfaces change the shape of the path of the sound waves. By precisely checking the phase of the ultrasound waves, we create curved sound paths that can go through obstacles and hit a specific destination.
The most important phenomenon in the game is what is called differential frequency generation. When two ultrasound beams overlap with slightly different frequencies such as 40 kHz and 39.5 kHz, they create a new sound wave with the difference between their frequencies – in this case 0.5 kHz or 500 Hz, which is in the human hearing area. Sound can only be heard where the rays cross. The ultrasound waves are silent outside of this intersection.
This means that you can deliver audio to a certain place or a specific person without disturbing other people up to date.
Promotion of sound control
The possibility of creating audio enclaves has many potential applications.
Audio enclaves could enable personalized audio in public spaces. For example, museums without headphones could provide different audio guides, and libraries could enable students to study with audio lessons without disturbing others.
In a car, the passengers were able to listen to music without distracting the driver from hearing navigation instructions. Offices and military environments could also benefit from localized language zones for confidential discussions. Audio enclaves could also be adjusted to cancel the sound in certain areas and create silent zones in order to improve the focus in jobs or to reduce noise pollution in cities.
This will not be on the shelf in the near future. For example, there are challenges for our technology. Nonlinear distortion can affect the sound quality. And electricity efficiency is another problem: the conversion of ultrasound into the audible sound requires high -intensity fields that can generate energy -intensive.
Despite these hurdles, audio enclaves present a fundamental shift in sound control. By redefining how sound interacts with the room, we open up new opportunities for immersive, efficient and personalized audio experiences.
This article will be released from the conversation, a non -profit, independent news organization that brings you facts and trustworthy analyzes to help you understand our complex world. It was written by: Jiaxin Zhong, Penn State and yun jing, Penn State
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Yun jing receives a financing of NSF.
Jiaxin Zhong does not work for a company or an organization that benefits from this article and have not published any relevant affiliations about their academic appointment.
