It is an acronym for Sound Navigation & Ranging (SONAR). Sonar is the technology of making use of sound waves to navigate, communicate and detect objects onor under surface of water. There are two types of Sonars today and they are:
What is Sonar Technology?
Active Sonar – It emits an acoustic signal or pulse into the water and if an object is in the way of the acoustic pulse then the sound bounces back and returns an echo to the sonar transducer. The sonar transducer in turn measures the strength of the signal. By determining the time between the emission of the acoustic signal and its reception, the transducer is able to determine the orientation and range of the object.
Passive Sonar - It is essentially listening to the sound made by vessels. It is primarily used to detect noise from marine objects like submarines and marine animals like whales. Passive sonar does not emit its own signals; it only listens to the sound waves coming towards it. This comes to help for military vessels who do not want to be detected, like submarines.
How does it work?
Active sonar consists of a transmitter, transducer, receiver & display.
An electrical impulse is sent out from a transmitter which is converted into a sound wave by the transducer and sent into the water. When this sound wave hits an object it rebounds. This echo strikes the transducer which converts it into an electrical signal which is then amplified by the receiver and sent to the display screen. In most cases the same transducer is used for transmission as well as detection of sound waves.
Now the question arises as how to detect the source of the sound and to understand the distance of the object from the ship. A sonar system constitutes of several hydrophones which act as sensors, and once a sound wave hits the hydrophones, each one will record the intensity of the sound along with the phase. Phase is nothing but the delay in timing to receive the sound wave. The sensor which will record the highest amplitude and will have the least delay in timing will be considered to be placed nearest to the origin/point of relection of the sound wave.
Another key factor which plays a crucial role in Sonar technology is the ocean environment. The performance of the sonar is highly dependent on the ocean environment which is highly unpredictable. Continued ocean studies for better understanding of the ocean are being pursued and better acoustic propagation models for accurate estimation of prediction ranges.
Scattering is one of the challenges which affect sonar technology. It is caused by small objects in the sea as well as from the bottom and surface. This proves to be a major source of interference. It is similar to scattering of light from a cars’ headlight in fog.
Applications of sonar technology
- Defence: Most military vessels carry sonar systems which are used to detect and track enemy vessels, torpedos etc. Both active and passive sonars are used for military applications.
- Bathymetric Studies: Using multi beam sonars or echo sonars to determine the underwater depth of ocean floors has not only given accurate results in determining the depth of the sea floor, but has also made navigation safer over the years.
- Pipeline inspections: Pipeline inspections can now be performed with high frequency side scan sonar which is used by oil & gas companies to detect spans, rock dump integrity & possible damage.
- Offshore wind turbines: High resolution sonars are often used for installation of huge offshore wind turbines as potential sites need to be surveyed accurately. It is also used for checking the seabed and also scour protection around the foundation of the turbine.
- Detecting explosive dangers underwater: As the seafloor gets increasingly exploited, it becomes equally important to identify objects before laying pipes, cables. Locating unexploded mines, bombs, torpedoes become increasingly important.
- Search and rescue missions: Side scan sonar systems are being used by Search & Rescue teams. It is essentially used to locate the body and once the target of a body is located with the help of a side scan sonar it guides the diver to the site for recovering the body.
- Underwater Communications: Dedicated sonars are fitted in ships and submarines for underwater communications.
- Inputs from Jith Joyson – CoreEl Technologies