An Australian search official... retired Air Chief Marshal Angus Houston, said... "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," ... [MH370 Black Box Rumors Unfounded: Search Leader]
The DailyMail article of April 10 sheds a little better light perhaps than NBC’s headline, on why Abbot may have sounded more enthusiastic than Houston. Note the comment by Capt.Matthews:
“Despite what Mr Houston described as ‘further encouraging findings’ he said that the underwater vehicle ‘Blue Fin 21’... would not be launched until the search area could be narrowed.
‘I believe we are searching in the right area, but....I’m not prepared to confirm anything until such time as somebody lays eyes on the wreckage.’
However, U.S. Navy Captain Mark Matthews said the detections indicate the device emitting the pings is somewhere within about a 12-mile radius. “
http://www.dailymail.co.uk/news/article-2602134/Aviation-expert-claims-black-box-MH370-located-search-crews.html
The "signal" referred to here is the fifth ping detected by an aircraft flying overhead -- not the previous 4 pings that they believe were from the black boxes:
Search leaders had said Thursday that a new possible signal had been located underwater by an Australian navy aircraft. Houston said early Friday that signal was unlikely to be from the missing Boeing 777.
Prime Minister Tony Abbott said in a speech Friday in Shanghai that searchers were confident that they knew the relative position of the black boxes, Reuters reported.
But Abbott cautioned that "confidence in the approximate position of the black box is not the same as recovering wreckage from almost 4½ kilometers beneath the sea or finally determining all that happened on the flight."