The new technology developed by the laboratory of the MIT laboratory uses a laser light to arouse moisture in the air around the ear of the target, causing a quiet whisper to a personal message a few meters away.
"Our system can be used from a distant far-off distant area directly to one's ear," says MIT's team leader and physicist Charles M. Vin.
We probably do not need to calculate potential applications for such a device, ranging from military applications to targeted advertising.
A pretty sound ambient noise is a problem – or headphones are inadequate – a whisper with a laser language can do the job.
In case you are concerned about all the work of a "laser in the ear", developers promise it is harmless.
"It's the first system that uses lasers that are completely safe for the eyes and skin to localize the sound signal to a particular person in any setting," said Wynne.
The technology that the channels sound in a narrow field is for decades.
Most of them use speakers to intensify sound waves or channel ultrasound in a small area. While they are useful for keeping the sound relatively limited, they require the listener to be a relatively short distance from the source.
Laser-based optical technology has a potential advantage of the reduced spread of distance, with higher frequencies that allow it to deliver much further – making the team turn from speakers to lasers.
The heart of the new MIT technology is a 1.9 mm tile laser. Thanks to the principle called photocoustic effect, water vapor in the air absorbs the emission of the laser, which causes vibration of the sound frequency.
"This can work even in relatively dry conditions, because there is almost always a little water in the air, especially around humans," says Win.
"We found that we do not need a lot of water if we use a laser wavelength that is much absorbed by water. This was the key because stronger absorption results in more sound."
The team tests two methods for transmitting sound. The former simply changed the amplitude of the laser through a modulator in a continuous wave, creating vibrations that could be taken from a microphone of 2.5 meters (8 feet).
The second process has destructed the modulator and used a mirror to accelerate the laser back and forth in terms of the speed of sound in what is known as dynamic photocoustic spectroscopy, which creates louder waves by jiggling more water particles.
"There are compromises between the two techniques," says the engineer of opto-mechanical Ryan M. Salenberger.
"The traditional photocoustic method delivers sound with greater loyalty, while the laser swing delivers sound with louder sound."
A potential drawback to the laser baking method is that it operates at a very specific distance from the transmitter. It was closer and the laser beam would be too high. Everything further, and the frequency falls under sensitivity.
Even though it was only tested in a range of 60 decibels (a level of normal conversation) a few meters, researchers believe they can increase distance and volume, now they have evidence of the concept.
"We hope this will eventually become a commercial technology," says Salenberger.
What means in the future someone might potentially whisper to your ear at considerable distances … something that is a bit disturbing and exciting at the same time.
This study was published in OSA publishing.