Active Sonar vs. Passive Sonar: Key Differences Explained

The Sonar system leverages sound waves to detect and locate objects underwater. It’s a valuable tool for identifying submerged objects and measuring their distance. Both active and passive sonar systems are widely used for underwater navigation, surveillance, and detection.

While active sonar emits sound waves to detect objects and measure distances, passive sonar relies on listening to sounds from external sources (equipment, propellers, marine life) without revealing its own position.

Understanding the differences between active and passive sonar, along with their advantages and disadvantages, is crucial for selecting the right technology for specific underwater applications.

Active Sonar

Here are the key features of an Active Sonar system:

• It consists of both a transmitter and a receiver.
• Active sonar transmits sound waves towards an object and receives the reflected waves.
• Active sonar sounds are emitted in pulse forms, and it listens for the echo after transmission.
• The reflected waves are used to detect the object and measure its distance.
• As active sonar transmits sound waves in the sea, it’s considered to be potentially harmful to marine life.
• Active sonar can detect vessels that are quiet and difficult to detect with passive sonar.
• Active sonar can detect marine mammals in shipping lanes or in high sound pressure zones.

Advantages of Active Sonar

• Provides accurate distance, speed, and position information.
• Can detect both moving and stationary objects.
• Effective in murky waters where visual detection is challenging.

Disadvantages of Active Sonar

• Can reveal the user’s position (e.g., a submarine) to others.
• Limited range compared to passive sonar in some environments.
• Can interfere with marine life due to emitted sound waves.

Passive Sonar

Here are the key features of a Passive Sonar system:

• It consists of a receiver only.
• It does not transmit sound waves but receives sound waves emitted by sea animals as they communicate, as well as other vibrations.
• Passive Sonar is used for detection of noise made by others (engines, propellers, animals, etc.).
• Passive Sonar often uses a large sonic database. Sonar operators classify signals using computers and stored databases to identify classes of ships and take appropriate action.
• As it does not transmit waves, it is considered to be safer for sea animals compared to active sonar.

Advantages of Passive Sonar

• Stealthy, as it does not emit any sound, keeping the user’s position concealed.
• Can detect objects at greater distances compared to active sonar.
• Can pick up a wide range of frequencies, providing detailed information.

Disadvantages of Passive Sonar

• Cannot provide precise distance or size information.
• Ineffective against silent or low-noise objects.
• Requires advanced signal processing to distinguish between different sources of sound.

Active vs. Passive Sonar: A Comparison

The following table compares active and passive sonar types:

Conclusion

Active and passive sonar are two complementary technologies used in underwater detection. While active sonar provides detailed distance and object information, it sacrifices stealth. On the other hand, passive sonar is ideal for covert monitoring but lacks the ability to measure distance accurately. Understanding these differences is essential for choosing the right sonar system based on operational needs.