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    High-resolution bathymetry of extinct asphalt volcanoes off the coast of California.  The bathymetry was collected using the autonomous underwater vehicle Sentry. (Image by Dana Yoerger, Woods Hole Oceanographic Institution)

Acoustics is the science of sound; ocean acoustics attempts to describe how sound behaves in the ocean. A strong understanding of how sound behaves in different conditions beneath the surface of the water or the seafloor helps scientists answer fundamental questions about the planet, the ocean, and marine life.

Sound travels much farther than light through water —in some cases, up to thousands of miles. The speed of sound in the ocean also varies, increasing with increases in temperature, salinity, and pressure (depth). These characteristics make sound an excellent tool to study questions about the physics, chemistry, and biology of the ocean  that would be difficult or impossible to approach any other way.

Ocean acoustics can involve detecting and interpreting naturally occurring sounds such as those made by whales and fish or earthquakes, as well as man-made sounds such as those made by ships. Scientists also purposely generate sounds in order to measure ocean currents, track temperature changes over vast areas of the ocean, or measure water depth and map the seafloor. Because sound travels well through solids scientists also use it to probe the structure of sediments and rocks deep beneath the seafloor in order to study such things as the geophysical processes that generate earthquakes, volcanoes, and tsunamis.