In 1992, the navy made hydrophones,underwater microphones, available to scientists. The purpose of these hydrophones was to track Soviet subs, but the navy heard more than just ships and subs. The hydrophones picked up the sounds of everything from rain to earthquakes, including the songs of the great whales.
Acoustical oceanography is dedicated to the science of discovering the ocean by listening.
For the first time scientists could listen to the ocean depths that were filled with the songs of the whales. The animals could be heard hundreds and even thousands of miles away. Instead of observing the ocean and hoping for a whale to pop up within the mile of a research ship, scientists were now able to study whales thousands of miles away. The whales songs travel so far because of their low frequency. The melody the whales sing is a slow pattern.