MIT has developed a system using lasers to transmit audio signals directly to the ear, and no one else in the area can hear them. As a nice bonus, the laser won’t burn your skin or eyes should you turn your head at the wrong moment.

Figure 1: lasers used to transmit audio signals directly to the ear

Figure 1 shows that the laser system leverages what is known as the photoacoustic effect. That simply means that the absorption of light waves by a material produces sound waves.

In this case, the light is absorbed by water molecules in the air, but the researchers learned to very carefully tune the laser to control where the sound appears. It’s essentially a narrow cone of sound.

Making sound with a laser is one thing, but creating specific tones or transmitting a message is much harder. The team evaluated two methods for doing this. [1]

How it works: To send the messages, researchers from MIT relied upon the photoacoustic effect, in which water vapor in the air absorbs light and forms sound waves.

The researchers used a laser beam to transmit a sound at 60 decibels (roughly the volume of background music or conversation in a restaurant) to a target person who was standing 2.5 meters away.

A second technique modulated the power of the laser beam to encode a message, which produced a quieter but clearer result. The team used it to beam music, recorded speech, and various tones, all at conversational volume. [2]

The key differences, of course, in the modern MIT system are that the receiver material is just ambient water vapor, and that the light is a precision laser. But the underlying concept is the same.The next step for the MIT device, the researchers wrote, is to try it outdoors and at longer range. [3]

References:

1. https://www.extremetech.com/extreme/284743-mit-creates-lasers-that-whisper-in-your-ear
2. https://www.technologyreview.com/2019/01/28/239657/lasers-can-send-a-whispered-audio-message-directly-to-one-persons-ear/
3. source: https://www.livescience.com/64619-laser-sound-beam.html

Cite this article:

Sri Vasagi K (2022), Audio Message Directly Can Hear Using Lasers, Anatechmaz, pp. 321