Learning from Dolphins How to Warn People about Tsunamis
Tsunami waves dozens of feet high when they reach shore may only be tens of centimeters high as they travel through the deep ocean. In order to reliably detect them and warn people before they reach land, sensitive pressure sensors must be located underneath passing waves in waters as deep as 6000 meters. The data must then be transmitted up to a buoy at the ocean's surface, where it is relayed to a satellite for distribution to an early warning center. Transmitting data through miles of water has proven difficult, however: sound waves, while unique in being able to travel long distances through water, reverberate and destructively interfere with one another as they travel, compromising the accuracy of information. Unless, that is, you are a dolphin. Dolphins are able to recognize the calls of specific individuals ("signature whistles") up to 25 kilometers away, demonstrating their ability to communicate and process sound information accurately despite the challenging medium of water. By employing several frequencies in each transmission, dolphins have found a way to cope with the sound scattering behavior of their high frequency, rapid transmissions, and still get their message reliably heard. Emulating dolphins' unique frequency-modulating acoustics, a company called EvoLogics has developed a high-performance underwater modem for data transmission, which is currently employed in the tsunami early warning system throughout the Indian Ocean.