Australian PM Tony Abbott thinks this is it.

Speaking to reporters during a state visit to Shanghai, the Australian leader said he was "confident" the sounds his search teams had picked up were coming from the plane's black boxes — and he also reminded us time was running out.

"It's been very much narrowed down because we've now had a series of detections, some for quite a long period of time," Abbott said, kicking off a round of speculation that authorities had found the plane.

"Nevertheless, we're getting to the stage where the signal from what we are very confident is the black box is starting to fade," Abbott added. "We are hoping to get as much information as we can before the signal finally expires."

However, the PM made his remarks at the same time as Australia's Chief Coordinator of the Joint Agency Coordination Centre, Air Chief Marshal Angus Houston, emailed reporters to say there had been no major breakthrough in the search for MH370.

“The Australian Joint Acoustic Analysis Centre has analysed the acoustic data and confirmed that the signal reported in the vicinity of the Australian Defence Vessel Ocean Shield is unlikely to be related to the aircraft black boxes,” Air Chief Marshal Angus Houston (Ret’d) said.

“On the information I have available to me, there has been no major breakthrough in the search for MH370,” Houston added.

Air Chief Houston said Ocean Shield would continue its "focused sweeps" with the towed pinger locator and that it was vital to glean "as much information as possible while the batteries on the underwater locator beacons may still be active."

Search teams have yet to deploy an Autonomous Underwater Vehicle, awaiting advice from experts on board the ship. That decision is days away, he said.

The conflicting remarks show the high hopes Australian PM Tony Abbott has that search teams will find the black box before its batteries die — if they haven't already expired.

Black boxes are built to last for 30 days, and as of Friday April 11 it's been 33 days since Malaysia Airlines Flight 370 vanished after taking off from Kuala Lumpur International Airport.

Image: AMSA

Search teams in the southern Indian Ocean said on Thursday they had detected yet another signal that authorities hope is coming from the black boxes on Malaysia Airlines Flight 370. That made five distinct signals in just a few days, which helped narrow the search area even more for teams who have been combing the seas for more than a month.

"The acoustic data will require further analysis overnight but shows potential of being from a man-made source," Australia's Air Chief Marshal Angus Houston said earlier Thursday, hours before downplaying the news of any breakthroughs.

Thursday's search area was smaller than previous days — about 22,400 square miles, or roughly the size of West Virginia — as teams believe they're getting closer to the site of MH370's final resting place.

Amanda Wills contributed to this report.