feet under water but only works for eight hours. schl onobuoys were not designed for this kind of mission. the ones that i m familiar with generally have very poor response to frequencies as high as 37 kilohertz. they are more for detecting mechanical signals from submarines, 1 kilohert or lower. reporter: the search continues to intensify. the british ship hms echo is now focusing where the pings have been detected. but crews continue to listen for even more pings to shrink the search zone. a smaller zone is necessary. the underwater vehicle can only search 40 square miles a day. that means the roughly 500-square mile area over a span