How does SONAR Work?

Ever wondered how fishers and commercial boats detect fish-populated areas in the middle of a large sea? Well, probably a SONAR is the best available technology over there. But what is a SONAR? Or questions like how does SONAR work?

This article will answer all the questions. If you are a fisherman or a technology enthusiast, this writing is for you to understand a SONAR better.

So without further ado, let’s get started.

What Is SONAR?

SONAR – Sound Navigation and Ranging – is a sensor that detects things by using sound waves. Among other uses, it is significantly important in mapping the ocean. The fishing industry uses it to identify the fishing zone, the sea level structure, and the surroundings.

SONAR identifies these things by sending ultrasonic waves into the water and measuring the returned echoes. A SONAR can detect the location, density, and motion of fish schooling at every point of the way at an angle of 360° or 180°.

Besides commercial boats, nowadays, tiny fishing boats and leisure boats also use SONAR due to its provisions.

Uses of SONAR

Some of the common uses of a SONAR device are as follows:

• Fishermen use it to locate areas of fishing
• Medical reasons like imagining cancer cells – also called a sonogram
• Submarines and warships by the military to find the track on the enemy
• Underwater communications
• Measure the sea depth and more things

And many more.

What Are the Types of SONAR?

There are three types of SONAR available. They are:

• Searchlight SONAR
• Sector Scan SONAR
• Scanning SONAR

Let’s know more details about them.

Searchlight SONAR (PPI SONAR)

The flashlight SONAR shows underwater data in a 360-degree perspective all-around vessel. It’s the same as using a spotlight to look at something around your boat. Continually rotating the sensor shows data such as fish schooling and sea currents in a 360-degree panorama surrounding the vessel.

On the screen, the SONAR is generally displayed as a point in the middle, followed by echoes in an all-around circle boat. Then it transmits ultrasonic waves from the sensor to the seafloor, in which they will reflect the sensor.

As the next ultrasonic pulse is sent, the sensor’s angle shifts. When the ultrasonic waves are delivered, the sensor instantly switches to the reception mode and listens for the ultrasonic echoes that return.

Sector Scan SONAR

The scanning SONAR simultaneously produces ultrasonic waves all around the boat in 360 degrees and can identify and show a lot of similarities in real-time.

The detection speed is significantly quicker than those of others, as well as the entire environment may be sensed instantaneously. Using this, you can identify and assess the movements of fast-swimming species in the water.

Scanning SONAR

The concept is the same as with the searchlight SONAR. However, the area scanning is in 45-degree increments. Thus it is 4 to 7 times quicker.

How does SONAR Work?

A screen, transducer, transmitter, and receiver are all part of an active SONAR system. An impulse is sent straight from the transmitter and is converted into a sound wave by the sensor. The sound will rebound when the wave collides with an item.

The echoes then rebound to the transducer that converts the sound into an electrical impulse that the receiver amplifies. This information is then transmitted to the screen.

Besides, a slew of hydrophone sensors records the sound’s strength. It also keeps track of the phase.

The time delay that occurs while hearing a sound wave will refer to as phase. The sensor with the highest amplitude and the least period is closest to the point of reflection.

Remember:

The performance of SONAR devices varies depending on the ocean’s environment, which can be unexpected at times. Regular ocean investigations are essential for acoustic propagation models to guarantee correct range estimation.

One of the examples is dispersion. This phenomenon causes by tiny items present in the water, ranging in size from the bottom to the surface. The same principle applies to this water interference as it does to light scattering from fog.

Operating Principles of a SONAR

Now, to understand a SONAR better, you’ve to know the following things:

Sound Speed

The SONAR system calculates the distance traveled by the sound by combining the sound speed in the water with the time the reflection receives.

The distance calculation is as follows:

Distance = (Speed of sound in water) x(calculated sound delay upon return / 2)

The sound speed in bodies of water is about 1500 m/s. However, it also varies on the operating depth of the process, water temperature, and salinity. So the distance mostly depends on the time delay, i.e. the time between sending and receiving the signal.

Although a SONAR system cannot compute sound speed precisely, the values in the display can give you an initial idea.

Target Reflectivity

SONAR focuses on the substantial material densities, such as metals, rocks, and gas. Since their densities are not the same as the water, the absorbed sound power will be different. Thus, the echoes from silt, mud, sand, and plants will not be as forceful. The SONAR represents the power with different colors such as – bright colors present loud echoes, while dark hues will give faint echoes in most palettes.

Sound Beam Patterns

Scanning SONAR is like a flashlight in a dark room when describing how it works in terms of sound. The user can only see the light-illuminated region – the remainder will stay dark.

Similarly, acoustic beams from SONAR have a defined height and width, which is the beam pattern compared to light rays. This acoustic beam uses sound energy instead of light energy to “illuminate” the intended water location.

Using the flashlight as an example, the beam moves over the area, and you can only see sections of the space illuminated. So, the transducer head spins using a servo motor swing in an arc to create sections of the entity to show images of things in the surroundings.

Bottom Visibility

It gives you a quality and clear image. While scanning the bottom of a waterbody, transmit power drops at greater distances.

If indeed, the method angles down and seems to have a low height at a hill, the screen may only show a small area. The SONAR device will highlight a larger expanse of the seafloor as it ascends in altitude.

The best SONAR outcomes can be achieved by controlling the elevation above the floor and inclined down.

Acoustic Shadow, Distance, and Altitude

When many objects are in a similar location and covered by shadows, it increases the produced angle and altitude.

Returning to the flashlight analogy, it refers to when a SONAR locates an item to establish its shape, direction, and height. These objects will have an acoustic shadow that will be lighted the same way as visible light.

The acoustic shadows will be short if the SONAR system has a sharp down angle and a high altitude. Short shades might be difficult to see, making it difficult to judge the object.

Object Visibility, Slant Range, Arrival Angle

Objects glow acoustically within the system’s beam patterns and reflect on the sensor.

Any items outside the pattern, whether below, outside, or above, do not appear on the SONAR viewer’s display. Scanning SONAR devices are unable to distinguish between objects with the same slant range.

For example, if two objects are in front of the SONAR at the same vertical range above each other, the SONAR will display them as a single item, despite being made up of a collection of their echoes.

Echoes in SONAR

The SONAR system frequently illuminates things at an angle, as described in previous portions of this essay. As a result, just the areas and sides closest to the method will be visible.

The loudest echoes will be produced by the surface of an object that is horizontal to the system. Areas with far less optimum angle, on the other hand, may cause the sound wave to reflecting off the system, resulting in poor outcomes.

Each of these sound concepts applies to big spaces. For example, when seeing ship bottoms and dock fingers in the sea, the light will reflect the details of the things in the line of vision. Zones concealed aside from the echo back will appear as no-return areas or as shades.

Industrial Applications of SONAR Technology

There are several uses of this technology, ranging from military purposes to deep-sea fishing.

For example, a SONAR can be used in bathymetric investigations. In this case, it detects the seafloor’s depth, ensuring the safe passage of the seas.

Gas and oil industry

A side-scanning technique with a high-frequency sensor can be used to check pipelines. Besides, gas and oil firms frequently apply this technology to identify damage, spans, and rock dump unity.

Underwater safety

Furthermore, in the construction of offshore wind turbines, a strong SONAR ensures safe installation. Underwater SONAR is used to identify explosive hazards. It is also critical to detect cables and pipelines in seafloors as they will explore.

Life-saving missions

SONAR is also commonly used in search and rescue operations. Side-scanning systems assist in locating bodies and directing divers to the location of the recovery. The technology used in submarines and ships allows them underwater sensor networks with other entities.

Active And Passive SONAR Systems

Active SONAR systems send an acoustic wave, or sound pulse, through into the water. When a sound vibration hits an item, the signal reflects off the thing and returns an echo to the SONAR device.

If indeed, the detector can receive signals, this represents the concentration of the signal. The sensor detects the speed and direction of the object by measuring the time difference.

Passive SONAR systems are commonly used to identify sound from marine surfaces and animals such as whales.

Unlike active SONAR, it doesn’t generate its own wave. Hence naval boats use who would not wish to be discovered and focus on silently “listening” to the water.

However, this only senses acoustic signals that are directed at it. Unless used in combination with specific hearing equipment, it cannot determine the range of an entity. A sound wave can be triangulated using several passive SONAR.

Advantages of SONAR

The following are the benefits of Sound Operated Navigation and Ranging:

• Sound waves are less attenuated in water
• The system’s implementation is not costly
• Reliability and accuracy are excellent

Disadvantages of SONAR

The following are some of the drawbacks of Sound Operated Navigation and Ranging:

• Scattering is the most common cause of Interfering
• Marine life is endangered
• The powerful beam of SONAR severely impairs directional accuracy
• The effect of resonance has an impact on the system’s performance

Conclusion

SONAR is a technique that detects the position of things in the water by using sound waves. During World War I, SONAR was created to help in the detection of submarines and icecaps. However, due to its various advantages, people are using it for multiple sectors.

Therefore knowledge of how does SONAR work can be advantageous in many ways. So what is your next project you want to implement this amazing technology?