In the underwater darkness, marine mammals use their own sounds and sounds made by other marine animals to navigate while migrating, to locate each other over great distances for mating, to find food, avoid predators, and care for their young.

Ocean noise is growing from a host of military, commercial and industrial sources including dredgers that clear the seabed for ship traffic, high explosives for removing oil platforms and testing naval vessels, construction pile drivers, harassment devices for fisheries, tunnel borers, drilling platforms, oil and gas surveys, ships, and commercial and military sonar.

Intense underwater noise can harm marine life in many ways. Military sonar has been linked to dozens of mass strandings of whales around the world, and oil and gas surveys have been shown to damage fish and reduce catch rates.