What is the difference between active and passive sonar?

What is the difference between active and passive sonar?

• A. Passive sonar listens for noises; active sonar emits pings and analyzes echoes
• B. Active sonar listens for noises; passive sonar emits pings
• C. Both listen for noises and emit pings
• D. Neither uses pings in detection

Answer: (B)

Active sonar sends out a sound pulse and then listens for the echoes to determine what’s in the water. The time it takes for the ping to travel to a target and back tells you how far away it is, and changes in frequency (Doppler shift) can reveal relative motion. This mode is powerful for range finding and mapping the underwater environment, but it also broadcasts sound that can reveal your own presence to others.

Passive sonar, on the other hand, does not emit any sound. It solely listens to noises produced by other vessels, marine life, or natural water sounds. It can indicate that something is there and, with directional sensing, narrow down where it’s coming from, but it cannot directly measure distance without additional measurements or techniques.

So the best description is that active sonar emits pings and analyzes echoes, while passive sonar only listens.