How Does a Sonar Work?


SONAR (Sound Navigation and Ranging system) is a common method used in several industries that utilizes sound waves to detect objects underwater. Most commonly it is used in the sea industry where it is utilized to detect fishes, vessels, submarines, and any other underwater hazards.

Sonar has made it easy for us to detect underwater objects embedded deep into the ocean. The equipment sends sound waves using its high technology, the waves or impulses then hit the nearby object, and then come back to the ocean surface which is detected by the sonar.

Sonar is used in fishing or water studies because it utilizes sound waves. Sound waves travel excellently under the water as compared to light or even radio waves.

How Does Sonar Work?

Sonar works on detecting the echoes which return back from the ultrasonic waves the sonar emits. Sonar is capable of detecting the structure, movement, and density of a fish at relative angles of 180 and 360 degrees.


Sonar is equipment that relies on sound waves to detect objects underwater. Sonar serves different purposes in different industries, but it’s the major equipment in the fishing industry where it is used exclusively to find fish under the sea, objects, and also the nature of the seabed. The major difference between a sonar and a fish finder is that a sonar detects a thing around the vessel while the fish finder works when the object is under the vessel.

Japan is majorly using fish sonars on multiple fishing vessels of various sizes like bonito ships, purse seiners etc. Sonars are primarily linked with trawlers because they are usually pictured with them. Now sonars are installed on every other boat including small fishing boats and even on pleasure boats etc.

How Does Sonar Work to Detect Underwater Objects?

Sonar is regarded as the latest technology to detect objects under the ocean. A sonar sends acoustic waves in order for object detection. Almost all sonar devices work on the same principle. Sonar consists of a component called ‘“transducer.” The transducer emits acoustic waves which are reflected back from the object. It calculates the time the waves take to reflect back from the object. The precise calculation of this reflection makes the sonar capable of detecting the objects underwater.

The sonar device is a marvellous piece of equipment in the fishing industry. Because of the sonar, the fisherman and the biologists are now capable of detecting fishes and objects which are not yet known to science.

It works on two basic principles:

“Sound waves and the reflection.” The sonar produces sound pulses which are sent into the water. As soon as these pulses hit an object underwater like fish, vegetation or any solid surface, they come back to the surface after hitting that object.

The sonar detects those reflected pulses and calculates the exact time it took the reflected sound waves to go into the ocean, hit the object, and then reflect back. The calculated time determines how far or distant is the object under the sea.

Does Sonar Work Only In Water?

Like radar, lidar sonar technology is also used to detect the size, shape, and structure of the objects, Mostly, the technology is used underwater because it relies on the reflection of sound waves.

Water is an excellent reflector of sound. It’s easier to detect the reflected sound waves in the water than in the air. That is why sonar technology is most commonly used under the water for fish and object detection. The transducer of the sonar is designed and meant to send waves in the water and then record the faintly reflected waves.

However, it is very difficult to mimic the process in the air. Because the reflected sound waves would be too faded away, they will become impossible to detect by the transducer. For detecting objects in the air, there is a different instrument other than sonar.

What Does Sonar Do?

Sonar is basically an instrument that becomes your eyes in the water. It helps you detect and see things deep inside the water. It takes the aid of sound waves to help you see under the water. The word SONAR is an abbreviation for “Sound Navigation and Ranging”, and is the equipment used to map out the ocean and for exploring the objects underwater.

Sonar is the best equipment to use underwater because sound waves travel way faster in the water as compared to light and radio waves. Scientists in NOAA exclusively use SONAR for the development of nautical charts.

Not only this, SONAR is extremely helpful to locate underwater dangers beforehand. It is primarily used to map out the ocean, and the objects on the seabed like wrecks of the ships, and map out the seafloor as well.

The major uses of the sonar include:

  • Ocean Mapping
  • Depth sounding
  • Acoustic location for drivers
  • Doppler Navigation

The success of the SONAR is primarily because of the “Transducer”, and the “Efficient acoustic projectors.”

How Does Fishing Sonar Work?

Fishing sonar is primarily meant for the fishing industry and is majorly used for detecting fish under deep water bodies. It’s difficult to locate fish in the deep oceans with a bare eye, and that is why we need special equipment to do the job.

A fish finder or fishing sonar will prevent you from aimlessly pointing in the water and getting nothing, instead the equipment will provide a graphic image of “what is under the water, and how far it is.”

In this way reaching towards a fish becomes way easier than aiming blindly in the ocean. Depending upon your SONAR, you may be capable of doing multiple things. Mostly, modern sonars are equipped with GPS, compass, and marine radar to help you locate objects beneath the water.

Read How Do Fish Finders Work?

How to install a fishfinder?

The sonar sends the sound impulses in the water and waits for the echo. The sonar then detects the reflected sound waves or echo to determine the distance, shape, and structure of the object aka fish. The sound waves a sonar emits can vary from high intensity (ultrasonic) to low intensity (infrasonic).

How Does Ice Fishing Sonar Work?

People interested in ice fishing can understand how difficult it is to locate the movement of the fish underwater. By using Ice fishing sonar, the objects and fishes can be easily detected under the water.

The ice fishing sonar displays the detected object in the form of an image on the circular screen. With the equipment, you can monitor the angler fish depth and also its distance relative to fish lure.

The ice fishing sonar consists of a flasher that looks like a cone that begins at the transducer and then expands to the bottom. The circumference of the cone becomes twice relative to the depth of the water.

For example, if you are ice fishing in 20 ft water, the cone’s circumference would be 5 feet. On the other hand, if the water depth is 4p ft, then the cone would be 10 feet wide.

Now the flasher detects the fish in two ways:

  • If the fish is moving around the cone or is on the outside of the cone the display would be green and yellow flashes on the screen.
  • If the fish is directly under the cone, the display would be a bright red light on the screen.

One can place the bait directly under the cone, and the fish will automatically come towards the bait. Since the bait is directly under the cone the fish movement will ultimately be detected starting from weak flashes of yellow/green to the bright red line.

How Does Sonar Fish Finder Work?

SONAR fish finder works on the basic principles of ‘sound’. It sends the sound pulses through the water waves. As soon as these sound pulses hit any object like fish, vegetation, and even to the bottom of the ocean, they are reflected back. The sonar then detects these reflected sound waves.

The Sonar calculates how long it took for the sound pulses to go into the ocean, hit the object, and then reflect back to the transducer.


All in all, SONAR is a technology primarily used underwater to detect and estimate how far an object is underwater. SONAR is diverse equipment and the basic principles are also used in medical science as Ultrasound.

Based on the basic principles of echo and reflection SONAR efficiently utilizes the sound waves that travel under the water and hit a specific object like fish, vegetation or the seabed. The SONAR then calculates the distance as the measure of time which the waves took to travel back to SONAR.

Ricki Cooper

I have been fishing for 11 years. I believe in the famous saying "If fishing is interfering with your business, give up your business".

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