PERTH, Australia — After a navy ship heard more signals from deep in the Indian Ocean, the head of the search for the missing Malaysian jetliner said Wednesday that he believes the hunt is closing in on the ‘‘final resting place’’ of Flight 370.
The Australian vessel Ocean Shield picked up two signals Tuesday, and an analysis of two other sounds detected Saturday showed they were consistent with a plane’s flight recorders, or ‘‘black boxes,’’ said Angus Houston, the Australian official coordinating the search for the Malaysian Airlines jet.
‘‘I’m now optimistic that we will find the aircraft, or what is left of the aircraft, in the not-too-distant future,’’ Houston said. ‘‘But we haven’t found it yet, because this is a very challenging business.’’
Finding the flight data and cockpit voice recorders soon is important because their locator beacons have a battery life of about a month, and Tuesday marked one month since Flight 370 vanished en route from Kuala Lumpur, Malaysia, to Beijing with 239 people aboard.
If the batteries fail before the recorders are located, finding them in such deep water — about 15,000 feet — would be difficult, if not impossible.
‘‘I believe we are searching in the right area, but we need to visually identify aircraft wreckage before we can confirm with certainty that this is the final resting place of MH370,’’ Houston said. ‘‘For the sake of the 239 families, this is absolutely imperative.’’
The hope expressed by Houston contrasted with the frustrating search for the Boeing 777, which disappeared shortly after takeoff in one of the biggest mysteries in aviation history. The plane veered off-course for an unknown reason, with officials saying that satellite data indicates it went down in the southern Indian Ocean off the coast of western Australia. The black boxes could help solve that mystery.
The signals detected 1,020 miles northwest of Perth by the Ocean Shield’s towed ping locators are the strongest indication yet that the plane crashed and is now at the bottom of the ocean in the area where the search is now focused.
A data analysis of the signals heard Saturday determined they were distinct, man-made, and pulsed consistently, Houston said.
‘‘They believe the signals to be consistent with the specification and description of a flight data recorder,’’ he said.
To assist the Ocean Shield, the Australian navy dropped buoys by parachutenear where the signals were last heard.
Royal Australian Navy Commodore Peter Leavy said each buoy will dangle a hydrophone listening device about 1,000 feet below the surface. The hope, he said, is the buoys will help better pinpoint the signals.
Houston acknowledged searchers were running out of time, noting the last two signals were weaker and briefer than the first pair heard Saturday, suggesting the batteries are failing. One lasted two hours and 20 minutes and the second lasted 13 minutes; those heard Tuesday lasted just 5½ minutes and 7 minutes.
The weakening of the signals also could indicate the device was farther away, US Navy Captain Mark Matthews said. Temperature, water pressure, or the saltiness of the sea could also be factors.
Leavy said silt on the ocean floor also could distort the sounds and may hide wreckage.
Houston said a decision had not yet been made on how long to use the towed ping locator, saying only that a decision to deploy an unmanned submarine in the search was ‘‘not far away.’’
When the ping locator’s use is exhausted, the unmanned sub will be sent to create a sonar map of a potential debris field on the seabed. The Bluefin 21 sub takes six times longer to cover the same area as the ping locator.
Matthews said the detections indicate the beacon is within about a 12-mile radius, equal to a 500-square-mile chunk of the ocean floor.
That’s like trying to find a desktop computer in a city the size of Los Angeles and would take the sub about six weeks to two months to canvass.