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How does sonar work?

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Quick answer

Sonar works by sending sound pulses through water and listening for the echoes that bounce off objects. By timing the echoes it measures distance and maps the seafloor, submarines, or fish — because sound travels well through water where light and radio don't.

Step by step

  1. A transducer emits a pulse of sound into the water.
  2. The sound reflects off the seabed, ships, or fish.
  3. The echo's return time reveals how far away the object is.
  4. Sound carries far in water, unlike light or radio waves.
  5. Active sonar sends pulses; passive sonar just listens for sounds.

People also ask

Why use sound underwater instead of light or radar?
Water quickly absorbs light and radio waves, but sound travels for kilometers, so sonar is the practical way to 'see' underwater.
How does sonar measure depth?
It times how long a sound pulse takes to bounce off the seafloor and return; knowing sound's speed in water converts that into depth.
What's the difference between active and passive sonar?
Active sonar emits its own pulses and listens for echoes; passive sonar stays silent and only listens for sounds others make.