Researchers at Perth's Curtin University are examining a low-frequency underwater sound signal that could have resulted from Malaysian Airlines Flight MH370 crashing into the Indian Ocean.
The signal was picked up by underwater sound recorders off Rottnest Island just after 1.30am (UTC) on March 8 - consistent with the disappearance of MH370 - but may have also originated from a natural event, such as a small earth tremor.
The signal has since been correlated with another underwater listening station, run by the United Nations' Comprehensive Nuclear-Test Ban Treaty Organisations, off Cape Leeuwin.
"Soon after the aircraft disappeared, scientists at CTBTO analysed data from their underwater listening stations south-west of Cape Leeuwin and in the northern Indian Ocean. They did not turn up anything of interest," Dr Alec Duncan, of Curtin, said.
"But when the MH370 search area was moved to the southern Indian Ocean, scientists from Curtin's Centre for Marine Science and Technology decided to recover the IMOS acoustic recorders located west of Rottnest Island. "
Data from one of the [Rottnest] recorders showed a clear acoustic signal at a time that was reasonably consistent with other information relating to the disappearance of MH370.
"The crash of a large aircraft in the ocean would be a high energy event and expected to generate intense underwater sounds." Dr Duncan said the timing of the signal made it of interest in the search for MH370.
"It has since been matched with a signal picked up by CTBTO's station south-west of Cape Leeuwin," Dr Duncan said. "A very careful re-check of data from that station showed a signal, almost buried in the background noise but consistent with what was recorded on the IMOS recorder off Rottnest."
The CTBTO station receives a lot of sound from the Southern Ocean and Antarctic coastline, which is why the signal showed up more noticeably on the Rottnest recorder.
"Using the three hydrophones from the Cape Leeuwin station, it was possible to get a precise bearing that showed the signal came from the north-west.
"Comparing the arrival time of the signal at the IMOS recorder with the time of its arrival at the Cape Leeuwin station, it was possible for Curtin's Centre for Marine Science and Technology team to come up with an approximate distance to the source of the sound along this north-west bearing."
But Dr Duncan conceded there were large uncertainties in the estimate and that it was "not compatible" with satellite "handshake" data transmitted from the aircraft, currently considered the most reliable source of information.
- Sydney Morning Herald