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How does sonar measure the distance between a ship and the seafloor?

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Cruise ship captain in uniform studies navigational charts with a compass on a table in the ship's bridge. — navigation Officers on a passenger ship using charts for navigation.

Sonar, which stands for "sound navigation ranging," measures the distance between a ship and the seafloor by using acoustic pulses. This process, often performed by an echo sounder, relies on the principle of timing the travel of sound waves through water.12

The measurement process works as follows:
* Transmission: A transducer converts electrical energy into an acoustic pressure wave, which is directed toward the seafloor.23
* Reflection: When the sound wave hits the seafloor, it reflects back toward the ship as an echo.23
* Reception: The same transducer (or a separate receiver) detects the returning echo and converts it back into an electrical signal.12
* Calculation: The system measures the total elapsed time between the emission of the pulse and the return of the echo. Because the speed of sound in seawater is known (averaging about 1,500 meters per second), the distance to the seafloor is calculated by multiplying one-half of the elapsed time by the speed of sound.34