Sonar (sound navigation and ranging) How does Sonar work? like radar is “eye in the sky” then Sonar is “eye in water”. So what is Sonar? Sonar is a device for observing (detecting, investigating) the existence and location of objects beneath the surface of the sea by using sound waves sent from the device and reflected back by the object (object) being observed, if more precisely the nose to see under water. Some modes of transportation that use it include ships, submarines and aircraft (for special purposes, usually on anti-submarine aircraft, where the sonar is needed to find the point where the submarine is).

Currently sonar has been widely used to detect submarines and mines, detect depth, commercial fishing, safety diving, and communication at sea. The emergence of sonar can not be separated from the pioneering figures like Daniel Colloden who in 1822 used an underwater bell to calculate the speed of sound under water on Lake Geneva, Switzerland. This was followed by Lewis Nixon, who in 1906 invented the first sonar-type hearing aid to detect the tip of the iceberg. Interest in sonar was even higher during World War I, when there was a need to be able to detect submarines. In subsequent developments there was the name Paul Langevin who in 1915 discovered the first sonar device to detect submarines using the properties of the piezoelectric quartz. Although he did not have time to get further involved in the war effort, Langevin’s work had a major influence on the design of the sonar.

How Does a Sonar System Work? The following simple example for example a conventional ship releases a signal into the water, then the reflection will give effect Echo (echo) and return it to the receiver system (receiver) well after that the recipient’s system does the calculation of the distance of the object from the location of the ship and also information information other things needed, such as sea mapping (sea measurements, sea topography, etc.). A sonar consists of a transmitter, transducer, receiver, and monitor screen.

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By knowing the speed of the measured media wave and by using the equation
s = v (½ t), then we will get the measured distance. The half factor in front of t above says half the travel time from the sonar to the reflecting site and back to the sonar. In other words, the time needed for waves to travel from sonar to reflectance.

At first Sonar only had a passive Sonar system, where no signal was sent out. But as technology advances and needs come an active Sonar where the signals sent can be received again. The frequency used by sonar is in the ultrasonic region, which is above 20,000 hertz. Because the frequency can not be heard and the wavelength in the ultrasonic region in the ultrasonic region is so small that the diffraction that occurs is also getting smaller, and the waves will not spread. The small wavelength used, can also be used to detect small objects as well.

What is the difference between Sonar and Radar? the difference between the two is in the source of the radiant energy and its propagation medium. Sonar that uses relatively high frequency sound waves. When on the sonar, sound waves propagate in the water medium while on radar, electromagnetic waves propagate in the air medium. It’s clear right? Now, what are the similarities of Sonar and Radar? the equation is nothing but the same as a navigation system and distance measurement.

What is Radar used for? radar, as explained above has many functions, ranging from the functions of geological surveys, Search and Reacue in the search for sinking aircraft or ships, military uses for example in submarines or anti-submarine aircraft, fishing for fishermen, and bottom mapping the sea and maybe many other functions. For Marine Surveys, usually the type of sonar that is used is the Side Scan Sonar, the side scan sonar is usually carried on an exploration vessel and looks like a blackhead and given a rope which is then put into the water. The sound waves used in side scan sonar technology usually have frequencies between 100 and 500 KHz. Wave pulses are emitted in a wide angle pattern towards the ocean floor, and the echoes are received back by the receiver in seconds. To find a particular location, recording needs to follow a certain survey trajectory using GPS positioning equipment and video plotter. Side scan sonar is able to make seabed recording coverage from both sides of the survey track. In calm sea conditions and a straight bow, sonograms can provide images that are as sharp and detailed as a photograph.

What about the level of Accuracy? Sonar accuracy is apparently influenced by the level of salinity (salt content) of the waters. Temperature and salinity change the water density, which can speed up or slow the signal back. Can Submarines avoid Sonar tracking? for military purposes the submarine infiltration generally moves in the “impermeable area” of airwaves (shadow zone). This area is a safe area where the temperature and salinity of the sea in the layer reflects the incoming sound propagation so that the ship can avoid detection of enemy SONAR, in addition to that technological advances have also made a submarine with special material to minimize reflections and electronic defense systems that can disrupt or damage the opponent’s active sonar system (jamming, scrambler system)

Did you know that Sonar Signal has a negative effect on marine mammals? (Negative Effects of Sonar) Excessive signal emission effects from sonar signals can interfere with the navigation of marine mammals such as dolphins and whales. In one case, a condition occurred where many dolphins were stranded in the sea because of the emission from sonar during a military exercise in the waters.

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