Curtin University researchers have been examining a low-frequency underwater sound signal that could have resulted from Malaysian Airlines Flight MH370.
The signal, which was picked up by underwater sound recorders off Rottnest Island just after 1:30 am UTC on the 8th March, could have resulted from Flight MH370 crashing into the Indian Ocean but could also have originated from a natural event, such as a small earth tremor.
However, there are large uncertainties in the estimate and it appears it is not compatible with the satellite 'handshake' data transmitted from the aircraft, which is currently considered the most reliable source of information.
Scientists from Curtin's Centre for Marine Science and Technology along with colleagues from the United Nations' Comprehensive Nuclear-Test-Ban Treaty Organisation (CTBTO) and Geoscience Australia have been involved in the search for sounds that might help with search efforts.
Dr Alec Duncan, Senior Research Fellow and part of Curtin's Centre for Marine Science and Technology team, explained that a passive acoustic observatory 40 kilometres west of Rottnest Island that forms part of the Commonwealth-funded Integrated Marine Observing System (IMOS) had provided the potential lead.
"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 Duncan 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 IMOS 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 signal could also have been due to natural causes - such as a small earth tremor - but the timing 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.
"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," Dr Duncan said.
"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.
Dr Duncan said Curtin's Centre for Marine Science and Technology team would continue to work with search authorities.
"Although we have now completed our analysis of these signals, Curtin's Centre for Marine Science and Technology still has several recorders deployed that could conceivably have picked up signals relating to MH370.
"Due to various factors, we consider it very unlikely that they would have done so and have therefore not recovered them to date. We will, however, be carefully analysing their recordings when they are recovered in due course," Dr Duncan said.