sound like this with this frequency. 37.5 kilohertz was selected because it is unique from the background noise in the ocean. randy joins us now. you ve been working with these beacons all day. how much water does it need be in before it starts pinging? reporter: they can survive in depths of 20,000 feet. what we want to show you tonight is how sensitive they are. we have this tin cup here. it has a moist paper towel in it. no water in it. this is one of the pingers. we have the tester right here. i ll be quiet for a moment as we put this in and just with a moisture paper towel listen to it activate right away. [ pinging sounds ] you hear that right away. it starts to work. we also want to tell you tonight we talked to the people here who make these and said we talked a lot about the 30 day deadline for the battery to run out
it s at a lower transmission frequency than the standard 37.5. a change possibly due to environmental factors. if there s a change in pressure on the ocean floor and the age of the particular batteries, the capacitants can change. reporter: they are guarding against intermission near the ocean shield. 375 miles away, search crews haven t given up hope on the other pinging sounds reported by the chinese. two search areas but so far neither has reacquired the sound they need. australian officials say they will keep searching for that pinging sound until there is absolutely no doubt the pinger batteries have expired.
randy joins us now. you ve been working with these beacons all day. how much water does it need be in before it starts pinging? reporter: they can survive in depths of 20,000 feet. what we want to show you tonight is how sensitive they are. we have this tin cup here. it has a moist paper towel in it. no water in it. this is one of the pingers. we have the tester right here. i ll be quiet for a moment as we put this in and just with a moisture paper towel listen to it activate right away. [ pinging sounds ] you hear that right away. it starts to work. we also want to tell you tonight we talked to the people here who make these and said we talked a lot about the 30 day deadline for the battery to run out because it only lasts 30 days. they said there s a three to five day grace period so that was good news we may have a few extra days. they talked about the fact
the transmission level. meantime, they are guarding against noise interference, limiting the number of ships and aircraft near the ocean shield. 375 miles away, search crews haven t given up hope on the other pinging sounds reported by the chinese. two search areas, but so far neither has reacquired the sound they need. well, australian officials say they will keep searching for that pinging sound until there is absolutely no doubt the pinger batteries have expired. that means roughly another ten to 12 days or so. at the same time, locating debris is still critical. search crews have deployed data buoys to monitor water flow in hopes of locating that debris. of course, that will help them trace back to that point possibly where the plane went into the water. all right, rene, stand by. we re going to get back to you. let s go to the base of operations right now, the base of the operations for the search, our senior international