can underwater audio signals solve aviation’s biggest mystery?

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Malaysian Airlines flight MH370 departed on 8 March 2014 with 239 people on board. Despite extensive search efforts, the final location of the aircraft remains unknown. It has become one of aviation’s greatest mysteries.

Our new research explores the possibility of detecting underwater acoustic signals generated by aircraft crashes, such as the estimated impact of MH370, to provide new insights into its fate.

Flight MH370 was en route from Kuala Lumpur to Beijing when it disappeared from radar screens. Official investigations indicate that it deviated from its intended route, heading southwest over the Indian Ocean. Despite multinational search efforts, including extensive underwater searches along and near the so-called “seventh arc” (the area determined by the last communication between the satellite and the plane), the main break.

Only a few pieces of debris washed ashore on islands in the Western Indian Ocean have been confirmed as part of MH370. That left the families of the passengers, the search teams and the world grappling with unanswered questions.

Acoustic analysis

Hydrophones are underwater microphones that pick up sound waves and pressure changes in the ocean. Such technology has shown promise in detecting pressure signals from various events, including aircraft crashes. These types of signals can travel thousands of kilometers, making hydrophones a valuable tool for identifying and classifying events in marine environments.

For our study, we analyzed data from the Comprehensive Nuclear-Test-Ban Organization (CTBTO) hydroacoustic stations. We focused on data from stations at Cape Leeuwin in Western Australia and Diego Garcia, an island in the Indian Ocean.

Both locations were operating around the time MH370 is believed to have gone down. These stations are located within ten minutes of signal travel time from the seventh arc. CTBTO stations have previously detected distinctive pressure signals from aircraft crashes, as well as earthquakes of varying magnitudes more than 5,000 kilometers away.

The mode of influence dictates the properties of the signal such as length, frequency range and loudness. By examining these signals, we hoped to identify any possible acoustic evidence of the MH370 crash.

Previous analysis by scientists at Curtin University and later by us confirmed a signal of an unknown source recorded at Cape Leeuwin station, towards the seventh arc. But it fell outside the time window suggested by the official search.

Our latest research focused on the official and narrow time window. The analysis identified only one relevant signal towards the seventh arc, recorded at the Cape Leeuwin station. But this signal was not found at the Diego Garcia station. This raises questions about its origins. We also examined data for signals along the initial flight path of MH370 but found no corresponding acoustic signatures.

With only a handful of past plane incidents, our findings are inconclusive. But a 200 tonne aircraft at a speed of 200 meters per second would release the kinetic energy equivalent to a small earthquake. It would be large enough to be recorded by hydrophones thousands of kilometers away.

Given the sensitivity of hydrophones, it is highly unlikely that a large aircraft impacting the ocean surface would not leave a detectable pressure signature, especially on nearby hydrophones. But unfavorable ocean conditions could dampen or mask such a signal.

Controlled explosions

To help resolve the debate about the detectability of the audio signal from MH370, a practical approach could be to conduct controlled explosions along the seventh arc, similar to those conducted for the ARA San Juan submarine.

On 15 November 2017 the ARA San Juan, operated by the Argentine Navy, went missing during an exercise mission. A few hours later CTBTO stations recorded an unusual signal. To aid the search, an air-dropped calibrated grenade was dropped two weeks later near the last known location.

The calibration grenade, also recorded by CTBTO hydroacoustic stations, was similar to the unusual signal radiated from the submarine explosion. The submarine was found a year later and all 44 crew members were lost.

A similar exercise could be carried out along the seventh arc, using explosions or air guns of energy levels equal to those believed to be associated with MH370. If the signals from such explosions showed a pressure amplitude similar to the signal of interest, it would support focusing future searches on that signal. If the signals detected at Cape Leeuwin and Diego Garcia are significantly stronger than the signal in question, further analysis of the signals from both stations would be required.

This may also lead to a re-evaluation of the data used to determine the seventh arc, considering new cases based on updated results. Additionally, variations in signal strength may provide insight into the conditions influencing variability, which may help better pinpoint areas of influence based on specific terrain and pathways.

So, while our research does not reveal the exact location of the MH370 crash, it highlights the potential of hydroacoustic technology to solve this aviation mystery. By refining our methods and conducting additional experiments, we may provide new insights into the fate of MH370 and improve our response to future maritime incidents.

The ongoing efforts to locate MH370 not only seek to bring closure to the families involved but also to enhance our ability to track and understand aviation accidents across vast oceanic areas.

This article from The Conversation is republished under a Creative Commons license. Read the original article.

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Usama Kadri does not work for, consult with, own shares in or receive funding from any company or organization that would benefit from this article, and does not she disclosed any relevant connections beyond their academic appointment.

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