One of the problems with gestures and tablets is that they are not always clearly visible from a distance — or in murky water — and the diver sending the initial message must make sure the recipient is already looking in their direction .
Unfortunately, radio communication is not an option, as radio waves don’t travel well underwater. While there are acoustic voice communication systems, they require expensive transceivers for both divers.
In search of a simpler and more affordable alternative, a team at the University of Washington has developed a smart shell that can be underwater.cell phoneapplication used on . Called AquaApp, it allows users to choose from 240 preset messages that correspond to the gestures used by divers.
To keep things simple, information conveying the 20 most commonly used signals is prominently displayed for quick access. In addition, the information can be grouped into eight subject categories, such as information related to environmental factors or equipment status.
Once a message is selected, the phone’s speaker sends it through the water as a series of acoustic pulses. These pulses are detected by the recipient’s phone’s microphone, and the app translates them into visual information on the screen. The app also reminds the recipient of the fact that the message has been received.
Thanks to a special network protocol, up to 60 divers can communicate with each other at one location at the same time. Based on field tests in various outdoor environments, the app is said to work well at a distance of 30 meters and transmit/receive SOS beacons from a distance of 100 meters.
There are complex factors to consider, including acoustic reflections from the seafloor, surfaces or underwater objects, background noise from sources such as boat engines, variations in the speakers and microphones of different cell phones, and the physical orientation of divers to each other.
For this reason, each time a “conversation” begins, the first phone emits a brief audible signal called a prelude. An app on the second phone analyzes the signal and uses it to determine the best way to send actual information under current conditions, such as the best bit rate and sound frequency. This information is transmitted back to the first mobile phone, which then sends the corresponding information.
Professor Shyam Gollakota said: “AquaApp brings underwater communication to the masses, and today’s underwater network is similar to ARPANET, the predecessor of the Internet in the 1970s, when only a few people had access to the Internet. Democratize to change that and make it as easy as downloading software on your smartphone.”
He led the research with doctoral students Tuoochao Chen and Justin Chan.