For journalists covering the search for Malaysian Airlines Fflight MH370 it has been a long, drawn out affair.

Daily vigils at the RAAF Base at Pearce north of here where the air search has been coordinated have produced bits and pieces from aircrews but nothing of substance.

At the beginning journalists were excited with sightings of "'objects"' seen in the murky waters of the Indian Ocean only to be told a day or so later that it was fishing junk.

The new focus now is Perth and the Joint Agency Coordination Centre (JACC).

The last couple of days have raised hopes that we may be getting closer to the site where MH370 crashed into the Indian Ocean with all 239 passengers and crew.

The daily briefings are staged managed for maximum effect.

Journalists are informed via e-mail that a press news conference will be held and are given an hour or two notices.

The venue is the media room at Dumas House — the West Australian government office building where JACC has commandeered an entire floor to coordinate the information flow.

Journalists mingle around the locked glass door talking until about 30 minutes before the pressnews conference when we are allowed into the small, windowless room where cameras are set up, sound and lighting tests done.

We are reminded to turn our mobiles on to silent. Then the wait for JACC head retired Air Chief Marshal Angus Houston and his team begins.

You get a sense that over the last couple of days the thousands of men and women manning ships and aircraft are now closing in on the site where MH370 may have crashed.

Australian Defense Force vessel Ocean Shield has now detected sounding sing that Houston says has given us "our most promising lead so far." But Houston inserts, as he often does, a note of caution.

"The information we have received over the last 24 hours must be treated with caution. We still have to locate the site of those soundings."

Houston and his team are cautious in what they say. The new leads are positive and could produce the best leads as to the crash site of MH370.

But the area where Ocean Shield is operating lies at the northern end of the search area. The water is deep 4,000 to 6,000 meters.

Locating the black box is now the priority. Monday was day 31 in the search for MH370. The battery life we are told of the black box is just 30 days although various experts say it could be 40 or 45 days.

Even so the pings or pulses that are transmitted at 37.5 kHz every second will start to fade out.

So far we have reports of sounds "consistent" "with those from a flight data and cockpit recorder. But as yet these soundings have not been positively pinpointed and the Ocean Shield towing its Pinger Locator is travelling at a laborious three3 to five5 kilometers an hour.

The next 24 to 48 hours will be critical in the search. An area has been narrowed down. To a 300 km corridor some 1,800 kms off the Western Australian coast.

While you sense an air of optimism during the briefing there is a sense that time is fast running out.

We are constantly re-minded that the search area is big and the water very deep.

We are asked not to build up the hopes or expectations of those who lost loved ones on board MH370.

And above all nothing so far has led us to a debris field scattered over the ocean floor.

No one is disputing the re-ports from Ocean Shield are the best leads so far in what has become one of the great aviation mysteries of our time.

How it got there could be contained in the black box. Finding it could take weeks, months or even years.