Signals coming from remote location underscore difficulty of recovering flight wreckage

While Chinese and Australian ships scouring the southern Indian Ocean have detected signals almost certainly emitted by the flight recorders of the missing Malaysia Airlines plane, there is still the question of how to locate debris even if the signals are confirmed to be from flight MH370's black box.

While news confirming the final location would be greeted with joy after a month of fruitless search, the big fear is that the wreckage of the plane is still in the middle of nowhere, reported the Wall Street Journal.

The signals were heard 570 nautical miles northwest of Exmouth, a remote Australian town 789 miles north of Perth. The town was set up in the late 1960s to house the families of US Navy personnel at the Naval Communication Station Harold E. Holt, reported WSJ.

The origin of the name is a strong reminder of the difficulty that awaits the second phase of the operation: Holt was an Australian prime minister who disappeared at sea while swimming off Victoria.

The paper said another detection of the signal would finally put the the 17-foot Bluefin-21 underwater drone into action. The sophisticated US-supplied drone could not be used earlier as there was no refined search area.

The task of defining a smaller search area has been left to the Ocean Shield, among many other ships. The Australian navy ship has been towing a ping locator, a yellow, stingray-shaped device known as the TPL-25 able to resist the pressure of thousands of feet of water and hear the faintest sound under the sea.

Once that is done, the Bluefin-21 could reveal the resting place of flight 370 and many of its 239 passengers and crew.

Since last Friday, both the Ocean Shield and China's Haixun 01 reported detecting signals four times with the longest one lasting an hour and 20 minutes, as announced yesterday by the head of the Joint Agency Coordination Centre in Perth, Angus Houston.

While Houston was excited about the latest development, describing it as the "most promising lead" so far, he was equally cautious as there could be many other sounds moving through water – known as acoustic energy – which are greatly affected by temperature, pressure and salinity.

"And that has the effect of attenuating, bending – sometimes through 90 degrees – sound waves. So it is quite possible and very hard to predict – it's quite possible for sound to travel great distances laterally but be very difficult to hear near the surface of the ocean, for instance," Peter Leavy, who heads the military task force conducting the search, told CNN. – April 8, 2014.