Des chercheurs du MIT ont mis au point un dispositif permettant d’envoyer un son directement à l’oreille d’une personne. Reposant sur un système de laser, il est capable de transmettre précisément un signal audio, de sorte que seul le destinataire puisse l’entendre.
Et si on pouvait transmettre les sons aussi précisément que la lumière via un laser ? C’est le résultat qu’ont obtenu des chercheurs du Laboratoire Lincoln, du MIT (États-Unis).
Lumière + vapeur d’eau = son
Les scientifiques se sont en effet inspirés du fonctionnement du laser. Leur système repose sur la photoacoustique, c’est-à-dire la génération d’ondes sonores à partir d’interactions entre la lumière et la matière. En l’occurrence, c’est la vapeur d’eau contenue dans l’air qui réagit avec l’émetteur laser élaboré par les chercheurs, pour produire le signal audio.
De plus, les auteurs de l’étude ont réussi à exploiter une longueur d’onde fortement absorbée par l’eau, ce qui permet d’augmenter la puissance et la qualité du son produit. Par conséquent, leur dispositif peut fonctionner même dans un environnement relativement sec, ne nécessitant qu’une quantité restreinte de vapeur d’eau.
Un « laser sonore » précis et sûr
Le système ainsi créé permet donc de générer un flux audio et de le transmettre de façon précise jusqu’à son destinataire, et uniquement à celui-ci, même dans un environnement bruyant. Et ce, sans risque pour les yeux ni la peau.
Les tests réalisés ont prouvé son efficacité à une distance de 2,5 m, ce qui reste encore assez limité. Mais d’après les scientifiques, ce résultat n’a été obtenu qu’avec du matériel disponible dans le commerce, et cette performance pourrait donc être aisément améliorée. Ce qui offrirait la possibilité de chuchoter à l’oreille d’une personne, à plusieurs mètres de distance.
Source : BGR
Toujours présenté pour une bonne cause, en omettant les graves dérives possibles. Il n’ échappera bien évidement qu’à l’auteur de l’article, que ceci rend obsolète les diagnostiques psychiatriques concernant la schizophrénie. Tellement insignifiant qu’il est absolument inutile de le mentionner… De même, est il bien nécessaire de parler de voice to skull, la « voix de Dieu » ?
WASHINGTON — Researchers have demonstrated that a laser can transmit an audible message to a person without any type of receiver equipment. The ability to send highly targeted audio signals over the air could be used to communicate across noisy rooms or warn individuals of a dangerous situation such as an active shooter.
New Technology Uses Lasers to Transmit Audible Messages to Specific People
Photoacoustic communication approach could send warning messages through the air without requiring a receiving device
WASHINGTON — Researchers have demonstrated that a laser can transmit an audible message to a person without any type of receiver equipment. The ability to send highly targeted audio signals over the air could be used to communicate across noisy rooms or warn individuals of a dangerous situation such as an active shooter.
In The Optical Society (OSA) journal Optics Letters, researchers from the Massachusetts Institute of Technology’s Lincoln Laboratory report using two different laser-based methods to transmit various tones, music and recorded speech at a conversational volume.
“Our system can be used from some distance away to beam information directly to someone’s ear,” said research team leader Charles M. Wynn. “It is the first system that uses lasers that are fully safe for the eyes and skin to localize an audible signal to a particular person in any setting.”
Creating sound from air
The new approaches are based on the photoacoustic effect, which occurs when a material forms sound waves after absorbing light. In this case, the researchers used water vapor in the air to absorb light and create sound.
“This can work even in relatively dry conditions because there is almost always a little water in the air, especially around people,” said Wynn. “We found that we don’t need a lot of water if we use a laser wavelength that is very strongly absorbed by water. This was key because the stronger absorption leads to more sound.”
One of the new sound transmission methods grew from a technique called dynamic photoacoustic spectroscopy (DPAS), which the researchers previously developed for chemical detection. In the earlier work, they discovered that scanning, or sweeping, a laser beam at the speed of sound could improve chemical detection.
“The speed of sound is a very special speed at which to work,” said Ryan M. Sullenberger, first author of the paper. “In this new paper, we show that sweeping a laser beam at the speed of sound at a wavelength absorbed by water can be used as an efficient way to create sound.”
Laboratory tests
In the lab, the researchers showed that commercially available equipment could transmit sound to a person more than 2.5 meters away at 60 decibels using the laser sweeping technique. They believe that the system could be easily scaled up to longer distances. They also tested a traditional photoacoustic method that doesn’t require sweeping the laser and encodes the audio message by modulating the power of the laser beam.
“There are tradeoffs between the two techniques,” said Sullenberger. “The traditional photoacoustics method provides sound with higher fidelity, whereas the laser sweeping provides sound with louder audio.”
Next, the researchers plan to demonstrate the methods outdoors at longer ranges. “We hope that this will eventually become a commercial technology,” said Sullenberger. “There are a lot of exciting possibilities, and we want to develop the communication technology in ways that are useful.”
Paper: R. M. Sullenberger, S. Kaushik, C. M. Wynn. “Photoacoustic communications: delivering audible signals via absorption of light by atmospheric H2O,” Opt. Lett., 44, 3, 622-625 (2019).
DOI: https://doi.org/10.1364/OL.44.000622.
About Optics Letters
Optics Letters offers rapid dissemination of new results in all areas of optics with short, original, peer-reviewed communications. Optics Letters covers the latest research in optical science, including optical measurements, optical components and devices, atmospheric optics, biomedical optics, Fourier optics, integrated optics, optical processing, optoelectronics, lasers, nonlinear optics, optical storage and holography, optical coherence, polarization, quantum electronics, ultrafast optical phenomena, photonic crystals and fiber optics.
About The Optical Society
Founded in 1916, The Optical Society (OSA) is the leading professional organization for scientists, engineers, students and business leaders who fuel discoveries, shape real-life applications and accelerate achievements in the science of light. Through world-renowned publications, meetings and membership initiatives, OSA provides quality research, inspired interactions and dedicated resources for its extensive global network of optics and photonics experts. For more information, visit osa.org.