Don’t you hate it when, after going just five or ten meters under water, you lose the signal completely? Now this annoying limitation of modern technology is being addressed by researchers at the University of Washington, who have created an underwater communication app that uses sonic signals to relay messages to your other submerged friends. It may sound crazy, but millions of people could use this technology in both recreational and professional diving situations.
The underwater communication problem is simple: radio waves are absorbed by water, and no signal our phones send or receive can travel more than a few inches without being completely lost. That’s one of the reasons submarines and the like need a chain: to send data back and forth to the surface.
Sound waves, on the other hand, travel quite easily through water and are used by countless aquatic animals to communicate. But not humans – because the way we make sound only works well in the air. So for as long as anyone can remember, divers have communicated with each other through hand gestures and other gestures.
Professional divers have a vocabulary of dozens of cues, from “low in the air” to “danger on your right” and anything you can think of that comes up during a dive. But you have to learn them, and see them when they are used to work; you can bet some divers wish they could pronounce a message the way they do over the waves.
That’s the idea behind AquaAppa software experiment from UW’s Mobile Intelligence Lab, led by PhD student Tuochao Chen and prolific professor Shyam Gollakota.
The system uses a modified form of “chirping” or using the phone’s speaker to create high-frequency audio signals to communicate data rather than radio. This has been done before, but not (to my knowledge) in such a simple, self-correcting way that any smartphone can use.
“With AquaApp, we demonstrate underwater messaging using the speaker and microphone commonly available on smartphones and watches. Aside from downloading an app to their phone, people only need a waterproof phone case suitable for the depth of their dive.” , Chen said in a UW press release.
It is not as simple as converting a signal to an acoustic signal. The conditions for transmitting and receiving are constantly changing as the location, relative speeds and environment of two people constantly change.
“For example, fluctuations in signal strength are exacerbated by reflections from the surface, floor and shoreline,” said Chen’s co-lead author and fellow student, Justin Chan. “Movement caused by people, waves and nearby objects can disrupt data transfer. We had to adapt to these and other factors in real time to ensure that AquaApp would work under real-world conditions.”
The app constantly recalibrates itself with some sort of handshake signal that the phones can easily hear and then report its characteristics. So if the tone is received from the sender, but the volume is low and the high end is attenuated, the receiver transmits that information and the transmitter can adjust its transmission signal to use a narrower frequency band, more power, and so on.
In their on-site experiments in lakes and “a strong wave bay” (probably Shilshole), they found that they could reliably exchange data over 100 meters — at very low bit rates, sure, but more than enough to run a set. of pre-programmed signals that correspond to the gestures of the old hand. While some (myself included) have lamented the loss of an elegant and very humane solution to a long-standing problem, the simple truth is that this can make dangerous diving much safer, or that recreational divers can communicate more than “help” and directions.
That said, diving is a pastime and a profession steeped in history and tradition, and this digital communication method is very unlikely to supplant gestures – an analog, self-powered alternative is just the kind of thing you want ready as a backup. have when things go sideways.
AquaApp’s code is open source and free to use — take a look and try it for yourself on this GitHub repo.