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 -- and they want to make this point -- just because they think they heard this sound from one of their pingers down toings it doesn't mean that the plane or pinger is right there. it radiates so widely. it could be far, far away. so they will have to narrow down the search area these search teams to try to fine it. >> i appreciate the demonstration. i want to bring back david gallow. and former department department of transportation inspector. you believe these pings are from black boxes. is there too much evidence for it to be anything else? >> absolutely. without a question in my mind they are. especially since we've gotten it from source we have. the china didn't seem very