The ocean has always been a noisy place. Before humans began intensive use of the ocean, sound in the ocean resulted from physical processes such as the breaking of waves, wind blowing across the surface, lightning strikes, ice cracking, and undersea earthquakes. Adding to this were biological sources of sound, from the sound of snapping shrimp and fish such as croakers, to the high-frequency vocalizations of toothed whales (e.g., dolphins, killer whales, and sperm whales) and low-frequency calls of baleen whales such as blue and humpback whales.
In the past several hundred years, human activities have altered the sound field in the ocean. Large-scale whaling and fishing of noise-producing species reduced sources of biological sound to the ocean. As industrial activities moved into the ocean, such as motorized ships, oil expoloration and extraction, and pile driving, this added new human-generated sound to the ocean. Sonar, developed and perfected in World War II, made it possible to locate submarines in the ocean by reflecting sound off them. Some oceanographers used sound to study various aspects of the ocean.
Sound has increased in the ocean over time, leading to an interest by many scientists in studying how this might be affect organisms in the ocean. Many individual scientists and small research groups have studied ocean sound and its effects on organisms for the past 60 years, but there has never been a large-scale international project of coordinated research. The scientific community believes that it is important to bring together scientists who study sound in the ocean and those who study its effects in the context of such a study. Thus was born the International Quiet Ocean Experiment.