(CNN) -- In a sea of uncertainty, two bits of good news emerged Wednesday.

Searchers picked up fresh signals that officials hope are locator beacons from the data recorders of the missing Malaysia Airlines Flight 370.

The Australian ship Ocean Shield had first picked up the underwater pulses Saturday. But then, for the next three days, nothing.

On Tuesday, the ship once again reacquired the signals. That's four signals in the same broad area: two on Saturday; two on Tuesday. All of the signals are within 17 miles of one another.

"I believe we are searching in the right area, but we need to visually identify wreckage before we can confirm with certainty that this is the final resting place of MH370," said Air Chief Marshal Angus Houston, who's coordinating the Australian operation.

The second piece of good news? Authorities analyzed the signals picked up Saturday and determined they weren't natural occurrences, but likely came from specific electronic equipment. Some marine life make similar sounds.

"They believe the signals to be consistent with the specification and description of a flight data recorder," Houston said. "I'm now optimistic. We'll find the aircraft or what's left of the aircraft in the not too distant future."

澳大利亚海盾号8日下午和晚上又监测到两次疑似信号，频率为33.3千赫兹。第一次监测时长为5分多钟，第二次监测时长为7分钟。海盾号第一次监测到信号的时间在5日下午4点多，第二次是当晚9点多，第三、四次分别是在8日下午4点27分和晚上10点17分。8日发现的信号能帮助澳方更好地缩小搜寻范围。澳大利亚专家团队正对海盾号侦测到的信号进行分析，对于失联客机上乘客的家属来说，这是一个非常重要的线索。海盾号今天继续展开搜索，并用声呐设备进行侦测，澳方将使用声波定位仪进行进一步的搜索，水下航行器也将开始工作。失联客机黑匣子信号一般只能在30天内发出，但现在已33天了，黑匣子电量减弱，需加紧搜索。因此澳方需要尽量获得更多信息，进一步确定位置。