If you have been reading the recent reports of underwater blackbox detection then you might have heard of the word sonar as well because the technique which is used for underwater detection of objects and for mapping the depth of the ocean’s is known as sonar. It is a pretty old technique but it is used to this day because of the increasing effectivity of this technique with the help of the latest technology.
What is sonar?
Sonar stands for Sound navigation and ranging and as we have mentioned about this for detecting objects as well as mapping the area which is underwater. Above the water it is also used by bats to navigate their way through the air. It works on the basic principle that sound in water or in any other kind of medium travels at a uniform speed and when it is reflected from a object or from a surface, it can be easily detected at what distance is that surface with the help of the speed of sound. Depending on the change and the variation in frequency in the reflected sound the nature of the object can also be calculated to a certain extent. That is why the procedure of sonar is so effective.
As mentioned above some of the commercial applications include mapping the underwater area as well as discovering something inside the oceans and studying the marine life and also sonar is used by Navy as well to keep a watch on the other vessels approaching in its area. Currently, the Navy’s are searching for the black boxes of the lost planes with the help of sonar as well.
How does a sonar work?
Vessel consist of a transducer and a detector and with the help of the transducer the ultrasonic sound is limited in the form of pulses and when this ultrasonic pulses are reflected from a surface it reflects back to the ship and is detected by the detector. Since the sound travels at the constant speed through water you can easily calculate the distance of the surface of the object from which it is reflected back to the detector. This enables the vessel to know at what distance is that surface or object. This is how a sonar works.
Types of sonar:
There are two type of sonar, one is known as the active sonar and the other one is known as the passive sonar. The working of both the would be explaining below.
Passive sonar, is a type of sonar which does not transmit the pulses but rather only collects the receiving pulses and it is used for hearing whether any other vessel is present in the vicinity or not. It is also used to monitor the marine life as well because dolphins as well as whales communicate with each other with the help of sound pulses and therefore marine biologists all over the world use passive sonar to detect their presence and to understand their signals.
Navy ships as well as submarines use this type of sonar to detect whether there is any other anime ship which is present in the vicinity. In order to test the performance of the ship, some of the ships leave behind a collective array of sonar detectors to listen to their own sound pulses to understand whether the ship is working properly or not.
Recently, this type of sonar was also used to detect the pings of the black boxes of the submerged to planes which were crashed in the sea. These black boxes are designed to send pings up to 30 days from the day of the crash and therefore the Navies all over the world, used passive sonar for the detection of these pings.
Active sonar, transmits and receives pulses very rapidly and it consists of a transmitter as well as a detector. When it sends a pulse, the time period between the sending of the pulse and the receiving of the pulse determines the distance of the surface from which the pulse was reflected back. The speed of the sound is pretty fast and also it is constant through the water as well and therefore by knowing the time difference between the transmission of the pulse and the reception of the pulse you can easily calculate the distance of the surface from which it was transmitted back. A concentrated pulse is transmitted in the direction in which the surfaces to be detected. Active sonar can be mounted on ships or on helicopters or even on small boats and it can be put in handheld devices as well.
Effect of sonar on marine life:
As we have mentioned in the article about dolphins as well as whales communicate with each other and also navigate with the help of sound pulses and therefore when the sound pulses which are emitted by the sonar interfere with the sound pulses it can have drastic impact on the dolphins as well as the whales.
There is scientific evidence that when US Navy used low frequency sonar that resulted in some fat and effects on the whales which came back to the surface quite soon as compared to the normal cycle which resulted in the decompression which proved to be fatal. There have also been instances when due to the low frequency sonar pulses the whales have beached and it was found that they had suffered from haemorrhages induced by those sound pulses. This resulted in the death of those whales. This coincided with the testing of the low frequency sonar by US Navy in the same area in 2000.
As it can be seen, sonar is actually a very useful and effective technology but if it is not used in a responsible manner it can play havoc for marine life and result in death of plenty of marine animals. Since that incident, there have been very few occasions when the marine animals have been impacted by sonar and looks like the technology is being put to proper use without putting the marine life in danger.