This diagram shows how a sonar system mounted on the bottom of a research vessel is used to "see" the seafloor. The transmitter sends pulses of sound energy (pings) through the water, similar to an underwater speaker. The receiver is like our eardrums. It detects return signals (echoes) that are reflected back from the seafloor or other objects in the water and/or on the seafloor, including living organisms. Depth is calculated by first knowing how fast sound travels in water (approximately 1,500 meters per second) and then measuring the time (round trip) between the transmitted ping and its returning echo. Sonar data can also be used to determine the shape and orientation of an underwater object.

Sonar: Seeing with Sound

SONAR, short for SOund NAvigation and Ranging, is a tool used to explore the ocean and locate objects underwater. Scientists use modern sonar technologies to develop nautical charts, locate underwater hazards for navigation, search for and identify objects in the water column or on the seafloor, and to map the seafloor itself. Click the link to the right to learn more about how explorers “see” the seafloor with sound in a print-friendly fact sheet provided by NOAA Ocean Exploration.

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