It was during a zoo visit in 1984 that Payne discovered low-frequency communication among land animals. Standing near the elephant cages, she felt a throbbing in the air—she compares it to "being in a car with the windows rolled up wrong"—and recalled her experience singing in a choir near a large pipe organ, where she could barely hear the sound in the lower registers but "the pressure was huge."
She suspected that the elephants were communicating with low-frequency vocalizations, and investigation proved that the animals were indeed rumbling at between 5 and 30 hertz. Subsequent field research revealed that infrasound plays a significant role in coordinating complex elephant societies over great distances. In the evening on the Namibian savanna, with a sound-reflecting temperature inversion overhead, a loud elephant call may fill an area as large as 300 square kilometers.
