It so happened that on the morning Malaysian Airlines flight MH370 went missing, March 8, a team of Australian oceanographers had an array of super-sensitive undersea microphones deployed along the western and northern coasts of the continent. In June, the research team, led by Curtin University's Alec Duncan, discovered that their mountains of acoustic data hid a tantalizing anomaly.
It was a peculiar sound, a distinct crash amid the low rumble of the deep sea. The team traced its source to the Indian Ocean, placing it somewhere on a long straight line extending northwest from Perth Canyon, the undersea Grand Canyon being explored by the hydroacoustic researchers, all the way to the Arabian Sea. The crash was non-specific, possible just a seismic rumbling, but it was also a rare shred of possibility for a hunt that's really had none since MH370 vanished that night in March.
The Australian team was able to confirm their finding with help from another organization interested in undersea acoustic anomalies, the Comprehensive Nuclear-Test-Ban Treaty Organization, which operates a global network of seismic detectors and other instruments designed to hunt illegal underwater nuke testing. Unlike the Curtin team's equipment, the "CTBTO's stations have two sets of three hydrophones separated by several kilometres, which—like a pair of human ears—allow listeners to get a fix on a sound's direction to within 0.5 degrees," according to a post at nature.com.
The anomalous signal first discovered in June now appears to be a false lead, according to an update in Nature. With help from additional data collected at a different sensor, it now seems much more likely that the crashing sound was geologic in origin. The signal probably originated somewhere along the Carlberg Ridge, which extends from near the Horn of Africa northeast almost to India. Rather than an airliner impacting the ocean surface, the sound was more likely "caused by an earthquake, underwater landslide, or volcanic eruption," Duncan told nature.com last week, effectively confirming the signal as a dead-end.
The MH370 search continues. A recent reexamination of satellite data has narrowed the search area down from 600,000 square kilometers to 60,000, according to the Economist, while intensive seabed mapping efforts of southern Indian Ocean have enabled the more effective use of "towfish," multi-beam sonar devices that get drug along deep, deep underwater behind surface vessels. To give some indication of the challenge ahead, this small but powerful fleet of search equipment has already been contracted out for a full year.