Underwater, no one can hear you scream, not if they’re in a plane. The general impossibility of being able to bridge the gap from sonar to radio waves has been a problem for people looking to build underwater devices that communicate with the outside world, but new research from MIT might provide an answer.
The surface of the ocean is a hard barrier for signals to cross. Above the water, communication typically happens using radio waves, which can travel through air for hundreds of miles. Underwater, however, radio waves can only travel a few inches before petering out. Instead, underwater communication, such as between submarines, underwater robots, or divers, typically uses sound waves, which can travel through water for miles.
The problem, of course, is that it’s tough to switch between radio and acoustic at the border between water and air. In the past, scientists and engineers have attempted to solve this problem with dedicated communications buoys, or simply by bringing subs and drones to the surface to send and receive signals. But researchers from MIT have developed a better way, by using sound waves to create small, detectable vibrations at the water’s surface.
The technology is still in the early stage, but here’s how it works. A powerful speaker beneath the waves sends sound waves toward the surface. These sound waves cause the water’s surface to vibrate almost imperceptibly, with the vibrating waves only a fraction of a millimeter high. That’s much too small for humans to detect, but a very sensitive radar system can pick it out easily.
The researchers suggest that by using two different sound wave frequencies, operators could send binary 1s and 0s, and thus any signal they want. Using this technique, submarines could send signals to passing aircraft, underwater robots could send information back to their operators, and crashed airplanes or sunken ships could send out messages to rescuers.
This technology has only been tested in a pool so far, and real life conditions could make it harder in practice. But if it becomes more common, it could make exploring and living under the waves much easier.