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 The signal, which could be from the plane's black box recorders,
brings to five the number of "pings" detected in recent days within
the search area in the Indian Ocean.
The first four signals were detected by a U.S. Navy "Towed Pinger
Locator" (TPL) aboard Australia's Ocean Shield vessel, while the
latest was reported by an aircraft picking up transmissions from a
listening device buoy laid near the ship on Wednesday.
"Whilst conducting an acoustic search this afternoon a RAAF AP-3C
Orion aircraft has detected a possible signal in the vicinity of the
Australian Defence Vessel Ocean Shield," Angus Houston, head of the
Australian agency coordinating the search, said in a statement.
The data would require further analysis overnight but it showed the
potential of being from a "man-made source", he said.
The mystery of Malaysia Airlines Flight MH370, which disappeared
more than a month ago, has sparked the most expensive search and
rescue operation in aviation history, but concrete information has
proven frustratingly illusive.
The black boxes record cockpit data and may provide answers about
what happened to the plane, which was carrying 227 passengers and 12
crew when it vanished on March 8 and flew thousands of kilometres
off its Kuala Lumpur-to-Beijing route.
But the batteries in the black boxes have already reached the end of
their 30-day expected life, making efforts to swiftly locate them on
the murky ocean floor all the more critical.
"We are still a long way to go, but things are more positive than
they were some time ago," Martin Dolan, chief commissioner of the
Australian Transport Safety Board, which is involved in the search
mission, told Reuters.
NARROWING THE SEARCH AREA
Up to 10 military aircraft, four civil aircraft and 13 ships
are involved in the search effort that has proven fruitless in
identifying any physical evidence of wreckage from the flight.
Efforts are now focused on two areas — a larger one for aircraft and
ships about 2,240 km (1,392 miles) northwest of Perth and a smaller
area about 600 km (373 miles) closer to that west Australian city.
The smaller zone is around where the Ocean Shield picked up the
acoustic signals and where dozens of acoustic sonobuoys were dropped
on Wednesday.
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Each of the sonobuoys is equipped with a listening device called a
hydrophone, which is dangled about 1,000 ft below the surface and is
capable of transmitting data to search aircraft via radio signals.
"That does provide a lot of sensors in the vicinity of the Ocean
Shield without having a ship there to produce the background noise,"
said Australian Navy Commodore Peter Leavy, operational head of the
Australian search.
But experts say the process of teasing out the signals from the
cacophony of background noise in the sea is a slow and exhausting
process. Operators must separate a ping lasting just 9.3
milliseconds — a tenth of the blink of a human eye — and repeated
every 1.08 seconds from natural ocean sounds, as well as
disturbances from search vessels.
An autonomous underwater vehicle named Bluefin-21 is also onboard
the Ocean Shield, and it could be deployed to look for wreckage on
the sea floor once the final search area has been positively
identified.
As with so many things in this unprecedented search effort, experts
say that will not be easy.
"Working near the bottom of the ocean is very challenging because
this is uncharted territory; nobody has been down there before,"
Erik van Sebille, an oceanographer at the University of New South
Wales, told Reuters.
(Editing by Lincoln Feast and Robert Birsel)
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