Farewell headphones, welcome directional sound. A group of scientists from the Penn State College of Engineering has created a technology capable of sending the sound exactly where you want, making it audible only to those who are in a specific point. The rest of the environment remains immersed in silence.
The discovery, published in the magazine Proceedings of the National Academy of Sciences (PNAS)unpublished scenarios for entertainment, private communication, tourism and urban mobility opens. Just imagine listening to a guide in a museum or road indications in the car, without disturbing anyone and without having to wear earphones.
Because the sound is so difficult to control in the open space
The sound is one vibration that propagates in the air in the form of wavesjust like light. The frequency of the waves determines its height: the slow ones generate serious tones, the rapid acute tones. But unlike light, the sound is subject to diffractiona phenomenon that takes him to spread in all directionsmaking it extremely difficult to direct it precisely.
This feature has always represented an obstacle for those who wanted to develop directional audio technologies. But today, thanks to the intervention of Advanced acoustic materials and intelligent use of ultrasoundthe situation has changed.
How the technology that creates personal sound enclaves works
At the basis of innovation there is the possibility of generating “Audible enclave”very precise areas where the sound becomes perceptible. The researchers used Ultrasonic bundles – frequencies higher than we can hear – capable of bend in space through the use of acoustic metasuperificationsmaterials specially designed to manipulate sound waves.
The mechanism takes advantage of the concept of non -linear acoustic. When two beams of ultrasound at slightly different frequencies, for example 40 kHz and 39.5 kHz, they cross, create one new sound wave at the frequency of their difference: in this case, 0.5 kHz, perfectly audible from the human ear. The sound can be listened to Only at the point where the two bundles meetwhile nothing else is perceived.
“We used ultrasound as audible sound vectors,” explain the researchers. “In this way, the sound is transported in space in silence, until they become audible at the desired moment and place”.
Potential applications: private audio, silent cities and intelligent vehicles
The experimental system is already able to transmit sounds one meter away with an intensity equal to 60 Decibelsimilar to the tone of a conversation. Although technology still requires improvements, its practical applications They are numerous and concrete.
Let’s think about museums in which each visitor can listen to his own personal guide without headphones, or a cars in which only the driver receives the vocal indications of the navigator. You could even reduce noise pollution in cities, avoiding the use of traditional speakers in public places.
The future of listening seems to be personalized, invisible and silentrevolutionizing our way of interacting with sound.
