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Difference Between Active SONAR And Passive Sonar : Explained

Last updated on November 24th, 2023 at 08:39 am

What is Sonar ?

Sonar Stands for Sound Navigation And Ranging. It is a technique used mostly to explore and map the ocean bed and detect objects under the ocean. There are two types of sonar and each has its own advantages and disadvantages. The types are,

  • Active Sonar
  • Passive Sonar

Why is Sonar used in water?

The sonar is widely used in ships and submarines to map the ocean bed or to detect objects underwater. The reason why sonar is widely used under water is that radar which uses electromagnetic waves tends to be absorbed and weakened beyond useful range in water medium. Whereas in contrast sound waves tend to travel effectively in water and die off quickly in air.

Active Sonar

Active Sonar means the sonar device has a transmitter and a receiver. It uses a technique of transmitting sound waves usually in varying frequencies from infrasonic ( very low frequency sound waves ) to ultrasonic ( very low frequency sound waves ) and receiving the wave bouncing off of an object and the time difference is used to calculate the distance between the object.

Distance = Time x Speed of Sound in medium / 2
Active Sonar

Passive Sonar

Unlike Active Sonar, Passive sonar does not have a transmitter. The passive sonar just has a receiver and detects the sound waves getting generated from the object itself. Since it doesn’t have a transmitter, identifying the distance between the objects can be hard. Inorder to identify the distance between the source multiple passive sonars can be used in conjunctions and using triangulation to find the distance.


Active Vs Passive Sonar

Sonar TypeActive SonarPassive Sonar
OperationEmits sound waves and listens for echoesListens for sound waves produced by other sources
SourceThe sonar system itself emits sound wavesRelies on sound waves generated by other objects or sources
Signal StrengthSignal is typically strong and controlledSignal strength depends on the source and distance
RangeCan cover longer distancesEffective in shorter ranges
Object DetectionCan detect both moving and stationary objectsPrimarily detects moving objects
InterferenceLess affected by background noiseMore susceptible to background noise
Applications– Submarine and ship navigation– Submarine detection and tracking
– Fisheries and marine research– Anti-submarine warfare
– Underwater mapping and surveying– Environmental monitoring

Sonar uses in Robots

Sonar is used in conjunction with Lidar (Light Detection And Ranging) sensor in mobile robots because the lidar gets penetrated into the glass medium which can create a blindspot and make robots generate a path through the glass. To avoid this, active sonars are used to detect those obstacles.

The Sonar is also used in cars in rear for parking assistance and braking when detected an obstacle behind.


In conclusion, sonar, or Sound Navigation And Ranging, is a valuable technology for exploring and mapping the underwater world. Its ability to propagate sound waves effectively in water allows for the detection of objects, mapping of the ocean bed, and navigation in marine environments.

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