The two signals were about 1,800 metres apart.
The ADV Ocean Shield detection Sunday came shortly after a Chinese patrol vessel, the Haixun One Zero, reported detecting two pulse signals Friday night, and then again Saturday at a frequency consistent with black box technology.
Malaysia Airlines flight MH370 vanished mysteriously about an hour after taking off for Beijing from Kuala Lumpur shortly after midnight March 8.
The Boeing 777-200ER was scheduled to land in Beijing the same day.
The 227 passengers on board included five Indians, 154 Chinese and 38 Malaysians.
