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Curtin researchers in search for acoustic evidence of MH370
MEDIA RELEASE Wednesday 4 June 2014

 

Curtin University researchers have used underwater sound recordings to come up with a possible estimate for where MH370 might have crashed into the Indian Ocean.

 

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 8 th 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 Alex 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 CapeLeeuwin.

“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.

High-resolution diagrams and a map detailing the estimated uncertainty region are
available to download through Curtin Media Images on Flickr .

Source: Curtin University

 

Maps from Curtin's Media Center
     
  Map yellow polygon shows uncertainty region for source location

Map showing estimated uncertainty region (yellow polygon) for the source of the signals shown in Fig. 1. Magenta points and text show the locations of the various recording stations. RCS is the CMST recorder west of Rottnest Island, HA01 is CTBTO station off Cape Leeuwin, and HA08S is the southern CTBTO BIOT/Chagos Archipelago array. The fix was calculated using data received at RCS and HA01. The signal was not received at HA08S which could be due to it being blocked by shallow water to the north or northwest of this station or poor coupling of the signal into the Deep Sound Channel due to an unfavourable seabed slope.

   
  HA01 spectrograms showing 01_34_50 arrival

This plot shows how the frequency content of the underwater sound arriving at the three HA01 hydrophones varies with time. The arrow shows the arrival time of the peak energy of the signal we have been analysing. A mathematical process called correlation can be used to measure small differences between the times of arrival of the signal at the three hydrophones, from which the direction of the source can be calculated. The relatively high noise levels below 25 Hz are probably from shipping.

   
  Signals received at Rottnest recorder and Cape Leeuwin

Acoustic signals recorded by the CMST sound recorder west of Rottnest Island (top) and by one of the hydrophones of the CTBTO's HA01 hydroacoustic station off Cape Leeuwin (bottom). Arrows show the arrival time at each station of the peak energy of the signal.

   
  IMOS Acoustic Observatory Off Rottnest Island
   
  CMST Acoustic Recorders

Programmed autonomous underwater acoustic receivers capable of underwater sound for many months

     


Q&A

S.Sadasivan 5 June 2014 at 9:30 am

Intriguing ! Excellent caution on findings !
Is it possible that the sound of aircraft still airborne with engine on (perhaps losing altitude as fuel is running out in the final moments of flight ) is also buried in the underwater recordings ?

Can raw digital time signals be made available ?

Wonderful work !

Best wishes
S.Sadasivan

  • Alec Duncan 5 June 2014 at 4:58 pm

    That is an excellent question. The huge differences between the properties of air and water mean that very little airborne sound makes it into the water and vice-versa. However, if a sound is loud enough in the air it can be detected underwater. For example submarine sonars can pick up the sound of the loud turboprop engines used on many maritime patrol aircraft if the aircraft is close enough to the submarine and flying low enough. If MH370 had flown within a few kilometres of an underwater receiving system at low altitude it would probably have been heard, however this is very unlikely to have happened.

    Alec


 
The Sound from CTBTO Hydrophone of Interest to Search for Missing Flight MH 370

 


This spectrogram represents the signal that was recorded by the CTBTO's hydrophones at the Cape Leeuwin station in Western Australia at 1:34:48 UTC on 8 March 2014. Researchers are examining the sound in connection to the missing Malaysian Airlines flight MH370. The spectrogram shows the signal broken up into time and frequency. The white line is a filtered version of the sound showing an unusual signal in the middle (heard at seven seconds into the recording). The recording is speeded up by a factor of 16 to make it audible to the human ear.

"Every day we detect dozens of signals at Cape Leeuwin and most of them are from earthquakes around the Indian Ocean and ice-breaking events in Antarctica. The signal of interest came from a direction that we don't normally see so it's certainly not an everyday occurrence. Relating it to the airliner is difficult, however, especially given the large uncertainty in where and when any impact may have happened." CTBTO hydroacoustic expert, Dr Mark Prior said.

 

The Hydroacoustic Network and how it works

The CTBTO uses hydroacoustic stations to monitor for underwater nuclear tests. Click for interactive map

Read more

 

CTBTO News
 

 

Above info integrated on interactive map

Related:
UN body reports signal trace from Malaysia Airlines flight  

 

 

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