First one "ping", then another.<br/> <br />A Chinese ship searching for missing Malayasi Airlines Flight 370 detected a second fleeting "ping" on Sunday.<br/> <br />Both sounds came from near where investigators think the plane went down on March 8 in the Indian Ocean.<br/> <br />Also on Sunday, the Australian defense ship Ocean Field detected a separate acoustic signal.<br/> <br />But that one came from a different part of the vast search area, some 300 nautical miles away.<br/> <br />Both vessels are trying to verify if the sounds came from the missing plane's black box recorder.<br/> <br />The Chinese say the two pings had the same unique frequency reserved specifically for black box recorders.<br/> <br />But they caution, too, that time to locate the plane's black box is running out.<br/> <br />(SOUNDBITE) (Mandarin) SURVEY CAPTAIN FROM THE SHANGHAI MARITIME CENTRE OF SURVEYING AND MAPPING, ZHANG LIANG, SAYING:<br/> <br />"These few days are crucial for locating the black box. The main problem is the battery of the underwater
