recorder captured an important sound. >> a noise was heard in the last second of the cvr recording. >> reporter: he didn't say what the sound was. european investigators told cnn affiliate france the voice recorder indicates an explosion. experts say the sound of a bomb would stand out on the recorder. >> they have a very, very distinctive sound pattern. and that's what they'll be looking for. >> reporter: a key concern tonight that isis if it's really behind this will try to replicate it. >> the fact that this attack was a successful from the terrorist point of view would certainly encourage terrorists continue pursuing this avenue and trying to look at other opportunities possibly in other airports. keep in mind there are many airports around the world that fly to the united states. and the loyalty of local