Could the key to improving underwater communication be a technology developed for landline phones in the '60s?
At a hackathon earlier this month in San Francisco, oceanographers and scientists from NASA, the California Academy of Sciences, University of California Santa Cruz, and other institutions gathered to figure out how to improve on the current tools of choice for marine researchers: waterproof paper and pencil. The event was hosted by iDive, which is launching an underwater iPad housing this fall. The company is founded by a marine biologist, and the technology originated from a research lab in Saudi Arabia funded by the king.
The winning team of four—all with science and tech backgrounds, including a 15-year-old developer—came up with ScubaTone, an iPad app that relies on old-school technology created by AT&T in 1963 called dual-tone multifrequency signaling, or DTMF for short.
"DTMF was invented 50 years ago for telephone lines before we had rotary disks," explains Roberto De Almeida, a Brazilian oceanographer and developer at Sunnyvale, Calif.-based Marinexplore and member of ScubaTone. "DTMF is nothing more than the sounds a telephone makes when you press the different buttons, each one sending a signal composed of two different frequencies."
With eight signals, the ScubaTone prototype allows users to program 16 messages—such as "Emergency" or "I need more air"—to correspond with each sound emitted from the iPad app.
"If you're a scientist doing specific research, you're going to tailor these messages to what you're doing," he added.
The use of DTMF helps overcome one of the biggest problems with underwater communication: the sea's noise. Sound travels four times faster in water than air, so faraway sounds, such as a boat motor, can seem much closer than they actually are. Because ScubaTone listens for DTMF's 16 signals, which are on different bands and don't interfere with each other, it can cut through the noise.
With a transmitter on a boat attached to a hydrophone, an underwater microphone, crew members can also use DTMF to send messages to faraway divers. "Since the boat is not limited by the iPad battery, it can send a very strong signal," De Almeida said, noting the sounds could potentially reach thousands of meters below sea surface, which far exceeds the range of iDive's 100-foot submersible housing.
Because the Scuba hackathon took place in an office building, none of the prototypes could undergo real-world underwater testing. "In a regular room, this is quite loud," De Almeida said. Based on the iPad's specs, the team estimates ScubaTone has a theoretical range of more than 300 feet in all directions underwater, and the sounds are strong enough to overcome physical obstacles, such as rocks.
The team aims to continue developing its prototype and do underwater testing to determine its actual range.
"If you're doing research, you need to have a more elaborate form of communication," said De Almeida. "We have a working prototype and need to polish it and make it better."