Chinese state news agency Xinhua reported it had not yet been determined whether the signal was related to the missing plane, citing the China Maritime Search and Rescue Centre.
Xinhua said a black box detector deployed by the ship, Haixun 01, picked up a signal at 37.5 kilohertz (cycles per second), the same frequency emitted by flight data recorders.
Chinese ship reports hearing 'pulse signal'
Patrol vessel Haixun 01 reported hearing a "pulse signal" with the same frequency emitted by flight data recorders as it searched for MH370 in the Indian Ocean.
Malaysia's civil aviation chief, Azharuddin Abdul Rahman, confirmed that the frequency emitted by Flight 370's black boxes were 37.5 kilohertz and said authorities were verifying the report.
There are many clicks, buzzes and other sounds in the ocean from animals, but the 37.5 kilohertz pulse was selected for underwater locator beacons on black boxes because there is nothing else in the sea that would naturally make that sound, said William Waldock, an expert on search and rescue who teaches accident investigation at Embry-Riddle Aeronautical University in Prescott, Arizona.
"They picked that (frequency) so there wouldn't be false alarms from other things in the ocean," he said.
Waldock cautioned that "it's possible it could be an aberrant signal" from a nuclear submarine if there was one in the vicinity.
If the sounds can be verified, it would reduce the search area to about 10 square kilometres, Waldock said.
Unmanned robot subs with sidescan sonar would then be sent into the water to try to locate the wreckage, he said.
John Goglia, a former US National Transportation Safety Board member, called the report "exciting," but cautioned that "there is an awful lot of noise in the ocean."
"One ship, one ping doesn't make a success story," he said. "It will have to be explored. I guarantee you there are other resources being moved into the area to see if it can be verified."
The overall current search area is a 217,000-square-kilomete zone in the southern Indian Ocean, about 1700 kilometres northwest of Perth.