COSTELLO: A British navy ship called the HMS Echo is now in the area where that Chinese crew detected two audio signals. The Echo is equipped with a state-of-the-art sonar that can map the ocean floor. As you know, two pinger detectors picked up sound within 350 nautical miles of each other. Rene Marsh joins me now with more. Good morning, Rene.</s>RENE MARSH, CNN AVIATION & GOVERNMENT REGULATION CORRESPONDENT: Good morning, Carol. So the HMO (ph) Echo again in that general vicinity of where that Chinese patrol ship detected those pinging sounds both on Friday and Saturday. Now, the goal is to try and find that sound again and either confirm or rule out that it is from the black boxes belonging to Flight 370. Now, keep in mind, this area is different from where the Australian ship, the Ocean Shield, detected pinging sounds on two separate occasions. The first one for two hours, the second for about 13 minutes. So, let's talk more about the HMS Echo. We do know that it is designed to chart the sea floor with state-of-the-art sonar capability. I want to show you two examples of the images this ship has generated in past missions. These images from July of last year when Echo made surveys of 20 shipwrecks on the seabed near Libya. So you're looking at what it's capable of doing. But on this particular mission near that Chinese ship, we know that Echo would be using two principle pieces of technology. The first one would be passive sonar. The second one would be active sonar. So the passive sonar simply sits in the ocean and it listens. It's listening possibly for that pinging sound. And the active sonar, what that would do, would feed out energy and waits for a return response. And that would help this vessel in locating debris. Carol.</s>COSTELLO: Fascinating. Rene Marsh, many thanks. I'm back in a minute.
Two Signals Detected; British Ship Echo in Area of Reported Pings