Search teams are running against time as the batteries of the black box flight recorders have a life of about 30 days, meaning they will shut down in the next two days.
The black box can provide audio record of what happened on March 8 before the Beijing-bound Malaysia Airlines jet with 239 people, including five Indians, crashed in the southern Indian Ocean.
Sounds also travel long distances underwater, Houston said, making it difficult to ascertain their sources.
If detectors were near a pinger, it would also pick up the signal for a more sustained period.
Houston also said that search authorities were informed today that Ocean Shield, an Australian naval vessel equipped with sophisticated listening equipment, has detected “an acoustic noise” in another area of the ocean.
The search co-ordinator insisted the latest developments should be treated as unverified “until such time as we can provide an unequivocal determination”.
“We are working in a very big ocean and within a very large search area, and so far since the aircraft went missing we have had very few leads which allow us to narrow the search area,” he said.
HMS Echo, a British navy ship equipped with advanced detection gear, is on its way to the area where the Chinese ship picked up the signals, Houston said.
It is likely to arrive tonight. Australian planes are also headed to the area.
Ocean Shield, which has a high-tech pinger locator borrowed from the US Navy, will continue to pursue the sound it heard. If that lead turns cold, it will move to the other detection area, a journey that will take at least a day, Houston said.
