Don’t you hate when, after diving five or ten meters under water, you lose the signal completely? Now this vexing 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 send messages to your other submerged friends. It may sound silly, but millions of people could use this technology in both recreational and professional diving situations.
The problem with underwater communication is simple: radio waves are absorbed by water, and no signal sent or received by our phones can travel more than a few inches without being completely lost. That’s one of the reasons submersibles and the like need a tether: to pass data back and forth to the surface.
Sound waves, on the other hand, travel through water quite easily and are used by countless aquatic species to communicate. Not humans though, 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 signals and other gestures.
Professional divers will have a vocabulary of dozens of signals, from “low air” to “danger to your right” and anything else you can imagine during a dive. But you have to learn them and see them being used for them to work; you can bet at least some divers wish they could send a message like they do over the waves.
That’s the idea behind AquaApp, a software experiment from the UW Mobile Intelligence Lab, led by doctoral student Tuochao Chen and prolific professor Shyam Gollakota.
The system uses a modified form of “chirp” or uses the phone’s speaker to create high-frequency audio signals to communicate data instead of radio. This has been done before, but not (to my knowledge) in such a simple, self-correcting way that any smartphone can use it.
“With AquaApp, we demonstrate underwater messaging using the speaker and microphone widely available on smartphones and watches. Other than downloading an app on their phone, all people will need is a waterproof case rated for the depth of their dive,” Chen said in a UW news release.
It’s not as simple as converting a signal to an acoustic one. The conditions for transmitting and receiving are constantly changing when the location, relative speed, and environment of two people are constantly changing.
“For example, fluctuations in signal strength are aggravated by reflections from the surface, the ground, and the shoreline,” said Justin Chan, co-senior author and Chen’s fellow student. “Motion caused by humans, waves, and nearby objects can interfere with data transmission. We had to adapt in real time to these and other factors to ensure that AquaApp would work under real conditions.”
The app constantly recalibrates itself with a sort of handshake signal that phones can easily listen to and then report on features. So if the sender’s tone is received but the volume is low and the top end is attenuated, the receiver sends that information and the sender can modify their transmit signal to use a narrower frequency band, more power, etc.
In their in-situ experiments in lakes and “a bay with strong waves” (probably Shilshole), they found that they could reliably exchange data over 100 meters, at very low bit rates, to be sure, but more than enough to include a set of preprogrammed signals corresponding to ancient hand gestures. While some (including me) may lament the loss of an elegant and very humane solution to a long-standing problem, the simple truth is that this could make hazardous diving work much safer, or allow divers to games communicate more than “help” and instructions.
That said, diving is a hobby and profession steeped in history and tradition, and this digital communication method is highly unlikely to replace gestures – a self-powered analog alternative is exactly the kind of thing you want to have ready as a backup if things are going well. oblique.
AquaApp’s code is open source and free to use – take a look and try it out for yourself in this GitHub repository.