More than four weeks after the disappearance of Malaysia Airlines Flight MH 370, officials are hopeful that faint "pings" heard by a Chinese and an Australian ship could be related to the vanished jetliner.
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As search crews and ships with sophisticated listening devices descend on the two locations, experts say finding the black boxes before they stop "pinging" could be the best chance for finding the wreckage and unraveling what happened on the missing plane.
However, in spite of the reports, experts remain extremely cautious about connecting the faint sounds to the elusive data recorders. The recorders -- or black boxes -- are equipped with an automatic "pinging" device to help search crews locate them; the battery is guaranteed to last 30 days, but could possibly fade over time.
Flight MH 370 disappeared on March 8, en route from Kuala Lumpur to Beijing, China, with 239 people on board.
Australian Air Chief Marshal Angus Houston urged caution about assuming the sounds could be linked to the vanished plane.
"This is an important and encouraging lead, but one which I urge you to treat carefully," Houston, who is coordinating the search, told reporters.
A Chinese ship, the Haixun 01 first detected a signal on Saturday for 90 seconds. An Australian ship with more sophisticated listening devices also detected an "acoustic event" in a different area, 300 nautical miles away.
Houston added that the sounds were "fleeting, fleeting acoustic events," and not the sustained pinging sound that is characteristic of the black boxes.
David Mearns, a search and recovery expert and founder of Blue Water Recoveries, said that it's unlikely that the two ships both heard the ping of the black boxes.
"It's impossible for them to have heard both black boxes. It's too far," Mearns said of the distance between the two ships.
Mearns said it is possible that either or both of the ships have a "false positive." But if one of the ships finds sustained pinging sounds, Mearns said the first step would be to try and confirm the location of the data recorder, which emit a ping every second at a frequency of 37.5 kilohertz.
Officials would likely triangulate by turning ships in a clover position to figure out where the data recorder and the wreckage are located, he said.
"You move away from it and it gets [fainter] it's like the game hot or cold," Mearns said.
Once the signal is triangulated, the ships could start the underwater part of the search and deploy deep ocean sonar to look for the plane.
However, Mearns said he was skeptical that either ship has located the device, because the sounds emitted were described as "fleeting." The black boxes would normally ping about once a second, and once the pings are identified they should be able to be reacquired by listening devices in the area, he said.
Mearns said no other oceanographic equipment would emit noises at the same frequency as the recorders, but that it's still possible to get false positives.
"It's the ocean; it can make a noise," he said.
Mearns, who worked on the recovery of Air France Flight 447, which crashed into the Atlantic Ocean in 2009, said in that investigation they also believed they had found the black boxes through "pings." However, the "pings" later turned out to be false positives that were believed to have come from whales. It took two years for investigators to find the data recorders in that crash.
If both of these pings are found to be false positives, search crews will be back at square one.
Since the recorders are only guaranteed to emit pings for 30 days, Mearns said it will be extremely difficult to find them now. While they may work longer than guaranteed, Mearns said that means they might last a few extra days not extra weeks.
"If they're still talking about a big, big search area and don't feel confident about those pings, chances are they're going to have go back to square one," Mearns said. "'Do we keep searching?' That's decision that they'll have to make."
The Associated Press contributed to this report.