talking that they're hearing an echo or a ping and a ping. they're hearing a ping at one frequency and a ping at another frequency. >> which would be entirely different. >> which would say it's from two different devices compared to an echo or something bouncing off the bottom or something in the water. >> that's the other question i have for christine. what are the odds that double echo or double ping could have been as simple as a bounce off of a thermal layer or cavern or mountain or other debris? >> well, actually, we're working -- they're working in very deep water. approximately 12,000 feet. it's very dense water. sound travels faster in deeper water. that 350-mile radius between the chinese ship and the ocean shield, it's very possible they're both getting the same sound, and it could be closer farther south. it's just traveling at that distance. because according to what i've