of the world's leading experts on elephant communication. >> katy payne: i love animals, right? i went to the zoo. >> simon: the elephant cage? >> payne: the elephant cage, and i began to realize that i was feeling a throbbing in my ears and in the air that i couldn't really explain. and i said, "you know, do you suppose that elephants are making sounds that are below the pitches that i can hear?" and we recorded for a month and, lo and behold, we found that elephants had a great many sounds that people didn't know about. >> simon: she gave us examples of sound that we can hear. ( elephant sounds ) >> payne: a sound which i interpret generally as "everything's in order." >> simon: "everything's okay with the world." >> payne: "everything's okay." >> simon: but then, how do you discover the meaning of these sounds? >> payne: you just watch and watch and watch, and record and record and record, and keep the two together. >> simon: which brings us back to andrea. once or twice a year, she visits cornell with her latest recordings. and you're giving the material with which they work