That would be an area roughly the size of Texas.

Mark Prior, an acoustics expert at the test ban organization headquarters, said that the sound might be consistent with an ocean impact or with some kind of a sealed, air-filled container that sank into the depths until the exterior water pressure caused it to crumple.

Mr. Prior said that the sound might have been reflected off a seamount, or underwater mountain, before it traveled to the two receivers. So the receivers’ data might be indicating the distance and direction of the seamount, not the origin of the noise.

The Australian government has funded the research at Curtin University, and additional experts in Canberra, the country’s capital, have also collaborated. The Australian authorities have been skeptical so far about ordering a new search thousands of miles away based on the noise.

Martin Dolan, the chief commissioner of the Australian Transport Safety Bureau, said last week that search operations would continue to focus on the narrow arc defined by the Inmarsat calculations.

Dr. Duncan and his team operate an undersea device off the coast of Perth that is mainly used to monitor the low-frequency cries of blue whales, the world’s largest mammals and one of its most endangered species. The team’s receiver, or hydrophone, records noises on an undersea data device, which is hauled up to the ocean surface every six months and its contents downloaded.

The team sailed out for an extra visit to pull up the recorder and recover the data after the search for Flight 370 shifted to the Indian Ocean. The noise was faint but detectable, prompting Dr. Duncan to request and obtain the test ban treaty organization’s data for March 8 from its receiver off Cape Leeuwin, 220 miles to the south.

The organization did not initially detect any noise, Mr. Prior said, because it was using a high threshold for confirming a noise, based on its experience with underwater explosions. The organization has since rechecked the records of its other operating hydrophone in the Indian Ocean, near Diego Garcia, but the noise was not detected there. Its undersea receivers continuously relay data by cable to shore, where it is uploaded by satellite to Vienna.