Ocean Sound Waves May Reveal Location Of Incoming Objects

2017-11-02T09:06:22+00:00 November 2, 2017|
Acoustic-gravity waves are sound waves that are typically produced by high-impact sources such as underwater explosions or surface impacts. Usama Kadri and his colleagues carried out experiments to see whether objects hitting a water’s surface produced a characteristic pattern in acoustic-gravity waves. (Credit: Jose-Luis Olivares/ MIT)

(Click to enlarge) Acoustic-gravity waves are sound waves that are typically produced by high-impact sources such as underwater explosions or surface impacts. Usama Kadri and his colleagues carried out experiments to see whether objects hitting a water’s surface produced a characteristic pattern in acoustic-gravity waves. (Credit: Jose-Luis Olivares/ MIT)

New acoustic analysis could pinpoint impacts by meteorites or possibly plane debris. The ocean can seem like an acoustically disorienting place, with muffled sounds from near and far blending together in a murky sea of noise. Now an MIT mathematician has found a way to cut through this aquatic cacaphony, to identify underwater sound waves generated by objects impacting the ocean’s surface, such as debris from meteorites or aircraft. The results are published this week in the online journal Scientific Reports.

(From MIT News/ by Jennifer Chu) — Lead author Usama Kadri, a research affiliate in MIT’s Department of Mathematics, is applying the team’s acoustic analysis in hopes of locating Malaysia Airlines flight 370, an international passenger plane that disappeared over the southern Indian Ocean on March 8, 2014.

Since the aircraft’s disappearance, authorities have confirmed and recovered a few of the plane’s parts. However, the bulk of the aircraft has yet to be identified, as has any reasonable explanation for its demise.

Kadri believes that if the plane indeed crashed into the ocean, it would have generated underwater sound waves, called acoustic-gravity waves, with a very specific pattern. Such waves travel across large distances before dissipating and therefore would have been recorded by hydrophones around the world. If such patterns can be discerned amid the ocean’s background noise, Kadri says acoustic-gravity waves can be traced back to the location of the original crash.

In this new paper, Kadri and his colleagues have identified a characteristic pattern of acoustic-gravity waves produced by impacting objects, as opposed to other sources such as earthquakes or underwater explosions. They have looked for this pattern in data collected by underwater microphones near Australia on March 8, 2014, within the time window when the plane disappeared.

The team picked out two weak signals likely produced on that date by two ocean-impacting objects. The researchers determined, however, that the locations of these impacts were too far away from the course that the plane is believed to have taken. Instead, the impacts may have been produced by small meteorites falling into the sea. Kadri says that if the entire plane had crashed into the ocean, it would have produced a much stronger, clearer signal.

“The fact that there was no strong signature might suggest that at least some parts were detached from the airplane before impacting,” Kadri says. “With better data filtering, we may be able to revisit the Malaysia Airlines mystery and to try to identify other possible signals.”

The paper’s co-authors include researchers from Cardiff University, where Kadri also serves as a lecturer, and Memorial University of Newfoundland.

At the speed of sound

Acoustic-gravity waves are sound waves that are typically produced by high-impact sources such as underwater explosions or surface impacts. These waves can travel hundreds…

Read the full story here: http://news.mit.edu/2017/ocean-sound-waves-may-reveal-location-incoming-objects-1026