Sound in the world's oceans originates from many sources, such as storms, animals, earthquakes, commercial shipping, marine construction, military activities, oil and gas exploration and production, and even clouds of bubbles. Sound travels through water far better than does light, which is why many marine organisms rely on their hearing to find prey, to avoid predators, and to communicate.Measurements taken over the last 50 years indicate an increase in some areas in anthropogenic noise emissions into the marine environment. The main sources include vessel traffic, seismic exploration, industrial activities and construction (e.g., pile driving, drilling, tunnel boring, dredging), military and commercial sonar, acoustic deterrent devices, oceanographic experiments, and explosions for underwater construction. While high intensity, impulsive noise sources, such as seismic testing and pile driving, are thought to pose the greatest risk of acute injury (Southall et al., 2007), lower levels of continuous, chronic noise have created serious healthimpacts for marine mammals. The largest contributor of anthropogenic noise to the marine environment is conclusively commercial shipping, particularly in the low frequency range (Ross, 1993, 2005; Andrew et al., 2002; McDonald et al., 2006, 2008; Hildebrand, 2009; Chapman & Price, 2011; Frisk, 2012).
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