The U.S. Navy team operating the towed pinger locator (TPL) onboard Australian defense vessel Ocean Shield detected pinging signals, April 6.
The detected signals are consistent with sounds that would come from a black box.
The TPL heard consecutive pings at one second intervals. At the time of detection the TPL was at a depth of 300 meters, which is well above the optimal search depth where a black box would typically be detected.
Upon detection, the Ocean Shield crew turned off as much noise-producing equipment as possible to reduce the chance of false alarms, and the signal was again held for over two hours at a TPL depth of 1,400 meters. The signal stregnth increased and then faded, as would be expected with the ship moving toward then away from the signal.
After the signal was lost the team reeled the TPL back in to prepare for a course change to a reciprocal course to get a better line of bearing in the contact location.