Don’t you hate it when you walk 5 or 10 meters underwater and you lose the signal completely? Now, researchers at the University of Washington are addressing this nagging limitation of modern technology by creating an underwater communications app that uses acoustic signals to send messages to other underwater friends. This may sound silly, but one million can use the technology for leisure and professional diving.
The problem of underwater communication is simple. Radio waves are absorbed by water, and no signal sent or received by our mobile phones can be lost completely beyond a few inches. This is one of the reasons why submersibles, for example, need tethers: to transfer data back and forth to the surface.
On the other hand, sound waves can travel easily through water and are used by countless aquatic species to communicate. But humans can’t, because the way we make sound only works in the air. As a result, divers have used hand gestures and other gestures to communicate with each other for as long as people can remember.
Professional divers have dozens of words for signals, from“Insufficient air” to“Your right is in danger” and any other signal you can imagine during a dive. But you have to learn these signals and see them in action when you use them; you can bet that at least some divers wish they could type a message like they do on a wave.
That’s the idea behind AquaApp, a software experiment at the University of Washington’s Mobile Intelligence Laboratory, led by doctoral student Tuoochao Chen and prolific Professor Shyam Gollakota.
The system uses an improved form of“Chirping,” or uses the phone’s speakers to create high-frequency audio signals to communicate data rather than radio. This has happened before, but not (as far as I know) in such a simple, self-correcting way that any smartphone can use.
“With AquaApp, we demonstrated underwater messaging using the widely used speakers and microphones on smartphones and watches. Besides downloading an app on their phone, the only thing people need is a waterproof phone case that matches their diving depth,” Chen said in a University of Washington press release.
It’s not as simple as converting a signal into an audio signal. As the position, relative speed, and surroundings of two people change, so do the conditions under which they are launched and received.
“For example, fluctuations in signal intensity can be exacerbated by reflections from the surface, the ground and the coastline,” said Chen’s co-lead author and graduate student Chen Yi, “And nearby human, wave and object-induced motion can interfere with data transmission.”. We have to adapt to these and other factors in real time to make sure AquaApp works in real-world conditions.”
The app constantly recalibrates itself with a handshake signal that the phone can easily hear and then report its features. So if the sender’s tone is received, but the volume is low, and the high end is attenuated, the receiver sends the message, and the sender can modify its transmission to use a narrower band, more power, and so on.
In their field experiments in lakes and“Strong-wave bays”(probably Shilshole) , they found that they could reliably exchange data over 100 meters-certainly, at low bit rates, but enough to include a set of pre-programmed signals corresponding to the old gestures. While some people (myself included) may regret the loss of an elegant, very human solution to a long-standing problem, the simple fact is, this could make dangerous diving work safer, or allow recreational divers to communicate more than just“Help” and instructions.
That is to say, diving is a pastime and occupation steeped in history and tradition, such digital communication is unlikely to replace gestures-analog, self-powered alternatives are exactly what you want as backups when things happen.