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Sonar Definition

What is SONAR?

The SONAR stands for Sound Navigation and Ranging. Here, Navigation signifies the process to detect the route or the direction towards the destination. Here, Navigation implies the method to detect the object under the water. Navigation can also be defined as submarine navigation. The Ranging signifies the distance between the device and the object. It means that SONAR is a device used to detect the objects under the water by sending sound waves or echo. Sound waves are preferred because it travels faster in water than any other medium (light waves or radar waves). Let's have a look at its definition.


SONAR or Sound Navigation and Ranging are a system or technology used to detect the objects under water by sending the sound waves that is further reflected by the objects.


  • SONAR was initially developed during World War I to detect icebergs and submarines.
  • Around the 1930s, the SONAR was used to detect the pool of fishes.
  • By the end of World War II, SONAR was used to detect and hunt whales in the oceans.
  • Many improvements were made, and the scientist started to use it in the oceanographic research.
  • The study of sound propagation under the ocean or sea saw a rapid development around World War II.
  • The term SONAR was proposed around 1942.
  • The study of life in oceans with the help of acoustic was implemented in the 20th
  • It was preferred in the biological as well as non-biological study. The non-biological study is the research of military operations, navigation, etc.
  • The active acoustic ranging devices were used to find the ocean depth and marine organisms.
  • SONAR was also used to detect and identify the invertebrates and fishes.
  • New technology and sensitive equipment were used in the SONAR with the development of the latest technology.


The Sound Navigation and Ranging system (SONAR) uses ultrasonic sound waves of high frequency to detect the object or organism underwater.

Working Process of SONAR

SONAR sends sound waves under the water in oceans. We can also say that it sends pulses of sound waves under the water. The phenomenon of reflected waves from the object is shown below:

Sonar Definition

The concept of SONAR is based on a similar phenomenon as shown above.

When these sound waves hit any object, such as whales, fish, submarines, etc., it reflects the source. Thus, the sound waves emitted by the source (SONAR) can be called a transmitter. It also acts as a receiver as it receives the sound waves reflected from the object. SONAR calculated the time difference between the sending and receiving of sound waves. With the help of time, the distance is calculated between the SONAR and the detected object.

The speed of sound is already known. Hence, SONAR can easily calculate the distance with the help of time between

Types of SONAR

SONAR uses either a transducer or acoustic waves to detect the objects underwater.

The process of detection of the objects is similar to the radar system. SONAR is categorized into two types, namely Active SONAR and passive SONAR.

Let's discuss the above types of SONARs in detail.

Active SONAR

The active Sound Navigation Ranging system uses transducers as the source for emitting sound waves. The transducers emit acoustic sound waves in the form of signals or pulses.

These waves pass under the water. As soon as the wave reaches the object, it reflects. The reflected wave from the object reaches the transducer. The speed of sound waves pulses is fixed. SONAR measures the time between the sending and receiving of sound waves. It helps in calculating the distance between the SONAR and the object. In similar ways, the depth of oceans, etc., can be easily calculated with the help of SONAR.

It is shown below:

Sonar Definition

Passive SONAR

Passive SONAR does not emit its own sound waves like Active SONAR. Thus, passive SONAR is commonly used for scientific research and military applications. Such applications do want their signal or waves to be found by others. Passive SONAR listens to the acoustic signals transmitted by the external sources.

Sonar Definition

The passive SONAR detects the upcoming sound waves from the object under water in the oceans. It can only measure the range if it is used in combination with the other passive listening devices.

SONAR Concept

The concept of Sound Navigation and Ranging systems arises from bat or whales. The bats emit echolocation sound waves at night. It helps them to catch the prey. The echoes transmitted by the bats reflect after striking the object (particularly insects). The reflected echoes help bats to determine the distance of the insect. Such a process is also known as bio-SONAR.

Sound waves have less attenuation in the water. Sound waves are also considered mechanical waves, which do not lose any energy inside the water.

Advantages of SONAR

The advantages of the Sound Navigation and Ranging system are listed below:

  • High accuracy
  • Faster speed
  • Less attenuation in water
  • Inexpensive
  • It is used for various water activities and oceanographic research.

Disadvantages of SONAR

The disadvantages of the Sound Navigation and Ranging system are listed below:

  • The sound waves emitted by the SONAR can interfere with the marine organism, threatening their lives.
  • High-frequency waves are required to overcome the losses under the water. Such high-frequency waves act as a threat to living creatures under the water.

Applications of SONAR

The applications of Sound Navigation and Ranging system are listed below:

  • Detection of water organisms.
  • Detection of underwater icebergs.
  • Detection of an underwater threat, if any.
  • Detection of submarines.
  • Detection of cancer cells in medical imaging is also performed using the method known as a sonogram.
  • Detection of enemy vessels in the military.
  • Detecting damages in the large pipelines carrying oil and gas.
  • Detection of the depth of the sea and oceans.
  • To determines the speed of the object present underwater.

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