Can you control sound direction? Imagine getting into the subway at peak time and power Listen to your favorite music without wearing headphones and without other people to hear it. It has been a team of researchers at the Faculty of Engineering of Penn State, in the United States, which has achieved this feat by developing a method capable of controlling the sound so that it can only be heard from a specific position. The new technology, described in a study published in the magazine Proceedings of the National Academy of Sciences (PNAS), the world of communication and entertainment could someday revolutionize.
What is the sound?
Let us briefly remember that Sound is a vibration That, like a wave, travels through the air. The Frequency of vibration This is what determines its tone: the low frequencies correspond to deep sounds, while the high corresponds to acute sounds. The sound is also subject to a phenomenon called diffractionby which waves tend to disperse in space as they move. And precisely for that, check of sound is extremely difficult.
How the new technology works
In the new studythe researchers managed to limit the point at which the sound by creating localized bags of sound areas, called “audible enclaves”. To do this, they used beams ultrasound Capable of self -plete, thanks to specialized materials called acoustic goals, and referred to the concept of non -linear acoustics. Ultrasound, sound waves with higher frequencies than we can hear, can penetrate through many materials and interact with objects in unique forms. “In our work, we use ultrasound as carriers of audible sound,” they explained to The conversation The authors of the study. “They can transport the sound to space silently, becoming audible only when desired.”
How to control sound
Specifically, for create an audible enclaveThe researchers used two ultrasound beams at different frequencies that, when crossing in space, generate a new sound wave at an audible frequency only in that precise area. “The key phenomenon in play is what is called the generation of difference frequencies,” add the authors, who explain that when two ultrasonic doors of slightly different frequencies, for example 40 kHz and 39.5 kHz, they overlap create a new sound wave, in this case of 0.5 kHz, which is fine audible For people. However, the sound is only heard where you cross your do, while outside the ultrasonic waves remain silent. “This means that it is possible convey Sound to a specific person or place without disturbing other people during propagation, “experts comment.
Applications
At the moment, researchers have managed to spread the sound at a distance of approximately one meter of the objective and reach a volume of about 60 decibels, equivalent to that of a conversation. And although technology must still be perfected, its potential capacity could find multiple in the future Applicationsfrom audioguías without headphones in museums to the private listening of indications in cars and the reduction of noise pollution in cities.
Article originally published in Wired Italy. Adapted by Mauricio Serfatty Godoy.
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