Sonar system
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Sonar, an acronym for sound navigation and ranging, is a method for detecting and locating underwater objects using reflected sound waves, with historical roots dating back to Leonardo da Vinci in 1490. The system has two main types: active sonar, which uses sound transmitters and receivers in various modes, and passive sonar, which listens for sounds without transmitting. Sonar is crucial for naval operations, finding lost vessels, but its use has adverse effects on marine life, particularly for species like dolphins and whales.
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Sonar system
- 3. Sonar (originally an acronym for SOund Navigation And Ranging) It is a method of detecting , locating ,and determining the speed of objects through the use of reflected sound waves . A system using transmitted and reflected underwater sound waves to detect and locate submerged objects The acoustic frequencies used in sonar systems vary from very low (infrasonic) to extremely high (ultrasonic).
- 4. We know that some animals (dolphins and bats) have use sound as a medium of communication and objects detection for millions of years
- 5. But use of the sound by humans in the water is initially recorded by Leonardo da Vinci in 1490: a tube inserted into the water was said to be used to detect vessels by placing an ear to the tube. Sonar was first patented by Lewis Richardson and German physicist Alexander Behm in 1913.
- 6. o Sonar is a device that is used to detect underwater objects using sound waves. o In this system a sound pulse is generated and sent underwater through a transmitter. o sound waves are reflected by the underwater object which are received at receiver. o The time taken by sound wave to come back is recorded. o And by knowing the speed of sound wave in water the distance can be easily calculated by formula. o Distance = speed x time
- 7. Sonar is of two types: Active sonar Passive sonar
- 8. Active sonar uses sound transmitter and receiver . And there are 3 modes of operation : Monostatic mode Bistatic mode Multistatic mode
- 9. Monostatic mode : when the transmitter and receiver are at the same place. Bistatic mode : when the transmitter and receiver are separated by some distance. Multistatic mode : When more transmitters (or more receivers) are used, again spatially separated.
- 11. Transmitter : The transmitter generates the outgoing pulse. It determines pulse width, pulse reception frequency, modulation and carrier frequency. Transducer array : The individual transducers are simple elements with little or no directionality. They are arranged in an array to improve the directivity index, which improves the figure-of- merit by noise reduction. Beamforming processor: The input/output of each transducer is put through a ,beamforming processor which applies time delays or phase shifts to each of the signals in such a way as to create a narrow beam in a particular direction.
- 12. Duplexer switch : it is a switch that toggles between transmitter and receiver. Synchroniser : Provides overall coordination and timing for the system. Reset the display for each new pulse in order to make range measurements. Receiver : Collects the received energy. The receiver may also demodulate the return if frequency modulation is used on transmission
- 13. Display : Puts all of the detection information into a visual format. There are several types: A-scan : the signal along a single beam for a portion of the listening cycle. A target appears as a raised section if it is in the beam. PPI(plan position indicator) : A top-down (geographic view). The sonar system must sequentially search individual beams which are displayed in their true or relative form. The strength of the return is represented
- 14. o Passivesonarlistenswithouttransmitting. o Passivesonarhasawidevarietyoftechniques foridentifyingthesourceofadetectedsound. o Passivesonarsystemhavelargesonicdatabase butsonaroperatorclassifysignalsbyuseof computerandusethesedatabasestoidentify classesofshipsandaction.
- 15. Sound propagation : Sonar operation is affected by variations in sound speed, particularly in the vertical plane. Sound travels more slowly in fresh water than in sea water. The speed is determined by the water's bulk modulus and mass density. The bulk modulus is affected by temperature, dissolved impurities (usually salinity), and pressure. Speed = 4388 + (11.25 × temperature (in °F)) + (0.0182 × depth (in feet)) + salinity (in parts-per-thousand ).
- 16. It is used to find the actual depth of the sea. Sonar systems are used to find lost ships and submarines. These are used in ocean surveillance systems. They are used by navy detect the locations of enemy submarines. They are used for under water security.
- 17. It has an adverse effects on marine animals like dolphins and whales ,that also use sound waves for their navigation. It leads whales to painful and often fatal decompression sickness. The sonar systems generate lot of noise High intensity sonar sounds can create a small temporary shift in the hearing threshold of some fish
- 19. Thanks for watching and listening … Now is there any questions?