Hearing someone in a crowded room can be almost impossible due to the propagation of the sound waves, but what if we can design audio with the same precision we can project?
MIT researchers have developed a system that can do just that, creating a streamlined audio stream that can be shot at the ears of a person in the same way a laser pointer launches a beam of light. It is accurate, safe and can transmit music and even speech to the target without being heard by others.
"Our system can be used remotely to broadcast information directly to the ear of someone," said Charles Wynn of Lincoln's Laboratory of Massachusetts Institute of Technology. "This is the first system that uses lasers that are completely safe for the eyes and skin to locate a beep to a person in any environment."
The system relies on photoacoustics, which is a sound wave resulting from the interaction between light and matter. The team developed a laser system that interacts with water vapor in the air to generate sound along a narrow path between the transmitter and the receiver's ears.
"It can work even in relatively dry conditions, because almost always there is little water in the air, especially around people," Wynn said. "We have found that we do not need a lot of water if we use a laser wavelength that is very strongly absorbed by the water. This was the key because stronger absorption leads to more sound. "
In testing, the system works well at a distance of 2.5 meters, using only equipment that is already commercially available, but researchers say it can easily be made even more powerful.
The ability to send targeted audio over long distances will obviously have its advantages, especially in emergency situations where background noise can block the ability of a person to hear important information. The team hopes to continue to deal with its system and explore potential applications in the near future.